A Sneak Peek at a Book Jacket (with Traces)

Posted on January 4, 2013 by TMartin

After returning from a two-week vacation in California with my wife Ruth, we noticed a cardboard tube awaiting us at home. Intriguingly, the mystery package, which was only about 60 cm (24 in) long and 8 cm (3 in) wide, had been sent by Indiana University Press, the publisher of my new book, Life Traces of the Georgia Coast. We were a little puzzled by it, considering that it couldn’t possibly contain complimentary copies of the book. (As of this writing, I still have not held a corporeal representation of the book, hence my continuing skepticism that it is really published.) What was in this mystery tube?

Front cover and spine of my new book, Life Traces of the Georgia Coast: Revealing the Unseen Lives of Plants and Animals (Indiana University Press). The book, newly released this month, is not yet in stores, but supposedly on its way to those places and to people who were kind enough to pre-order it. But if you didn’t pre-order it, that’s OK: you can get it right here, right now.

Upon opening it, we were delighted to find that it held ten life-sized prints of the book jacket: front cover, spine, back cover, and front-back inside flaps. The cover art, done by Georgia artist Alan Campbell, looked gorgeous, and had reduced well to the 16 X 25 cm (6 X 9″) format, retaining details of traces and tracemakers, but also conveying a nice aesthetic sense. I was also amused to see the spine had the title (of course) but also said “Martin” and “Indiana.” Although I’ve lived in Georgia for more than 27 years, I was born and raised in Indiana, so it somehow seemed fitting in a circle-of-life sort of way to see this put so simply on the book.

Back cover of Life Traces of the Georgia Coast, highlighting a few of the tracemakers mentioned in the book – sea oats, sandhill crane, sand fiddler crab, and sea star – while also providing a pretty sunset view of primary dunes, beach, and subtidal environments on Sapelo Island. (P.S. I love that it says “Science” and “Nature” at the top, too.)

I had no idea what the back cover might be like until seeing these prints, but I thought it was well designed, bearing a fair representative sample of tracemakers of the Georgia barrier islands: sea oats (Uniola paniculata), a sandhill crane (Grus canadensis), sand fiddler crab (Uca pugilator), and lined sea star (Luidia clathrata), as well as a scenic view of some coastal environments. I had taken all of these photos, so it was exciting to see these arranged in such a pleasing way. My only scientifically based objection is that I would have like to see it include photos of insects, worms, amphibians, reptiles, or mammals (these and much more are covered in the book), as well as a few more tracks, trails, or burrows. Granted, I suppose they only had so much room for that 6 X 9″ space, and thus I understood how they couldn’t use this space to better represent the biodiversity of Georgia-coast tracemakers and their traces. (Oh well: guess you’ll have to read the book to learn about all that.)

Inside front and back flap material for Life Traces of the Georgia Coast, which also includes a summary of the book (written by me) and a rare photo of me (taken by Ruth Schowalter) in my natural habitat, which in this instance was on St. Catherines Island, Georgia.

I had written the summary of the book on the inside flap nearly a year ago, so it was fun to look at it with fresh eyes, almost as if someone else had written it for me. Fortunately, I banished my inner critic while reading it, and just enjoyed the sense that it likely achieved its goal, which was to tell people about the book and provoke their interest in it.

In short, this cover jacket symbolizes a next-to-last step toward the book being real in my mind. Now, like any good scientist, all I need is some independently verifiable evidence in the form of tactile data, such as a physical book in my hands. Stay tuned for that update, which I’ll be sure to share once it happens. In the meantime, many thanks to all of the staff at Indiana University Press – who I’ll mention by name next time – for their essential role in making the book happen and promoting it in this new year.

Information about the Book, from Indiana University Press

Life Traces of the Georgia Coast: Revealing the Unseen Lives of Plants and Animals, Anthony J. Martin

Have you ever wondered what left behind those prints and tracks on the seashore, or what made those marks or dug those holes in the dunes? Life Traces of the Georgia Coast is an up-close look at these traces of life and the animals and plants that made them. It tells about the how the tracemakers lived and how they interacted with their environments. This is a book about ichnology (the study of such traces), a wonderful way to learn about the behavior of organisms, living and long extinct. Life Traces presents an overview of the traces left by modern animals and plants in this biologically rich region; shows how life traces relate to the environments, natural history, and behaviors of their tracemakers; and applies that knowledge toward a better understanding of the fossilized traces that ancient life left in the geologic record. Augmented by numerous illustrations of traces made by both ancient and modern organisms, the book shows how ancient trace fossils directly relate to modern traces and tracemakers, among them, insects, grasses, crabs, shorebirds, alligators, and sea turtles. The result is an aesthetically appealing and scientifically accurate book that will serve as both a source book for scientists and for anyone interested in the natural history of the Georgia coast.

Life of the Past – Science/Paleontology

692 pp., 34 color illus., 137 b&w illus.
cloth 978-0-253-00602-8 $60.00
ebook 978-0-253-00609-7 $51.99

More information at:

http://www.iupress.indiana.edu/catalog/806767 ]http://www.iupress.indiana.edu/catalog/806767

The Traces We Leave Behind: A Tribute to Jordi Maria de Gibert

Posted on September 28, 2012 by TMartin

Paleontologists have an odd relationship with death. We often joke about how our livelihoods depend on what has died before us, or we experience great delight when we find an exquisite fossil, which probably was buried alive for it to be so well preserved. We also blithely talk about “death assemblages” and happily explain this gruesome term to non-paleontologically inclined students, friends, spouses, and partners without much thought about how it sounds to people outside of our field.

For ichnologists, who mostly study the tracks, burrows, and other vestiges of these lives that preceded us, our perspectives become even more skewed. Once-live animals, through their behavior, made trace fossils. Yet we almost never see what made them. Hence we also spend much of our time among the living, watching them make traces that we can use as analogs for those trace fossils left by their ancestors. Sometimes we find ourselves identifying with modern animals, developing empathy for what they experience as they form traces, a sensitivity that can extend to their trace-fossil equivalents. Hence for ichnologists, these parts of the fossil record become just a bit less removed from death, and we end up feeling for our tracemakers, both long gone and extant.

Jordi Maria de Gibert, contemplating and lamenting the loss of dinosaurian tracemakers from mass extinctions. The window display was in Basel, Switzerland, one of many places visited by Jordi in his quest to learn all things ichnological. (Photograph by Anthony Martin, who is also pictured in the reflection, along with ichnologists Luis Buatois and Gabriela Mángano, taken in 2003.)

In this sense, our small and close-knit international community of ichnologists was shocked to learn about the sudden loss of one of our own “tracemakers” this past weekend, Jordi Maria de Gibert. His death was unexpected and its impact accentuated because he and the rest of us had just gathered together only last month for the International Congress of Ichnology (Ichnia) in St. Johns, Newfoundland. We also anticipated seeing him again in his home city of Barcelona in 2016, where he died on Sunday. None of us had prepared ourselves to reflect on his legacy, let alone contemplate the possibility that his cognitive traces would cease any time soon.

The aftermath of the first Ichnia football match (sometimes known as “soccer” to you Yanks) between ichnologists of Team Gondwana and Team Laurasia, which took place on a pitch near Trelew, Argentina. Jordi, in the middle of the back row, is either signaling “Peace,” “Victory,” or, most likely, ordering two beers: one for him, and one for you so he can sit down to argue about trace fossils with you. (Photograph by Anthony Martin, taken in 2004.)

Most of our dismay about Jordi’s departure is because we loved him as a person, but it is also surely connected to our witnessing an ascendancy cut short. For instance, at the end of the meeting in St. Johns, Jordi addressed all of us as the newly elected president of the International Ichnological Association, and he had volunteered to serve as the main organizer for the next Ichnia meeting four years from now. His larger-than-life personality was on full display during his informal and impromptu speech: enthusiastic, cheerful, witty, earnest. In the days before then, he delivered multiple presentations on ongoing research projects, most of which revolved around his continuing interests in crustaceans and their traces, as well as those of marine bioeroders, animals that make a living by boring into rocks. Jordi was a prolific publisher of peer-reviewed papers on these topics, and was well known for his cooperative spirit, coauthoring with many ichnologists and other types of paleontologists on these papers.

Jordi (right, seated), in his preferred life habit, talking about fossils with colleagues (and friends) at an outcrop. And this wasn’t just any outcrop, but was at Mistaken Point, Newfoundland, which has one of the most spectacular Ediacaran fossil assemblages in the world. This had to have been a dream come true for him, as it was for many of us.

Jordi showing off his “Bama booties,” required footwear for the sacred ground of Mistaken Point, as some other ichnologist vainly attempts to “photobomb” him with his own blue-footed bootie. (Photograph by Ruth Schowalter.)

I had known Jordi since 1995, having first met in Bornholm, Denmark at a small ichnological meeting there. He and I were still new to our discipline (we were about the same age) and quite green, but eager to learn from our elders. As is typical with many academic friendships, over the next 17 years we would see each other at various meetings, and by my count we saw trace fossils and toasted one another in six countries (Denmark, U.S., U.K., Switzerland, Poland, Canada). Each time together, I grew more impressed with his intense and tenacious will to seek out more knowledge, digest it, and pass it on to others. He was a fierce intellectual who relished the debating of ideas, and was never satisfied with a conversation if he did not leave it wiser. This, of course, benefited all who were brave enough (and lucky enough) to enter into such discussions with him.

A happy time at the Ichnia 2004 banquet in Trelew, Argentina, with (from left to right) Renata Guimarães Netto, Jordi, and Ludvig Loewemark, where the exchange of ideas and good cheer flowed nearly as fast as the wine.

Jordi was young as far as ichnologists go, and as I argued in my previous post, the best ichnologists are the most experienced ones. So he knew as well as any of us that gaining more experience in the field was essential, and traveled to many places and studied traces of all ages – from the Ediacaran to the present – and traces of all kinds, from plant roots to dinosaur tracks. Accordingly, because of his dedication and broad interests, he had already become one of our best. In this vein, one of the metaphorical jokes ichnologists tell is how our academic success can be measured by how deeply we can burrow: shallow tiers are the least successful, whereas the deepst tiers are the most successful. Jordi was assuredly well on his way to the deepest tier, but we are all saddened about his unexpectedly reaching the historical layer before so many of us.

Los quatros amigos, posing happily toward the end of an ichnology field trip in Switzerland in 2003: from left to right, ichnologists Noelia Carmona, Gabriela Mángano, Luis Buatois, and Jordi, sporting some distinctive headgear and proudly flouting conformity. (Photograph by Anthony Martin.)

I learned about Jordi’s death on Sunday through our mutual ichnologist friend, Renata Guimarães Netto, who had likewise known Jordi for more nearly 20 years. Quickly the word spread through social media, e-mails, and phone calls, our sadness multiplying and magnifying worldwide. Only last month, we had celebrated with him, and now we mourned him, and expressed our sorrow to his family members, and close friends.

To ease some of this pain and enjoy an otherwise beautiful Sunday in Decatur, Georgia, my wife Ruth and I went for a walk. Without thinking, I suggested that we meander in one of the largest, quietest green spaces in Decatur, which turned out to be its cemetery. (Yes, I know. All I can say is that the subconscious is more powerful than we know.) While we strolled, I thought about times spent with Jordi on field trips and in conferences, while also recalling papers he had written and discoveries he had made. As mentioned earlier, Jordi’s interests were varied, but perhaps his favorite research topic was crustacean burrows, especially the burrows of crabs, shrimp, lobsters, and other 10-legged crustaceans. Too bad we were nowhere near the Georgia coast, I thought, as it would have been a fitting and comforting homage for Ruth and I to take in the many decapod burrows of the Georgia beaches and salt marshes, which Jordi had never seen in person.

That’s when an eerie coincidence happened. During our walk, we spotted a former pond on the cemetery grounds, now drained for dredging. There’s something about a big pit of mud that appeals to every ichnologist, so I excitedly suggested that we go take a look to see what traces were there. We expected to find lots of tracks, such as those of birds, raccoons, squirrels, and coyotes, and maybe a few other urban fauna. Instead, though, the muddy surface was perforated by decapod tracks and burrows.

Need to see some crustacean traces, but you live in the landlocked part of Georgia? Just go to a dried pond and look for tracks like these.

These were the traces of crayfish, decapods that diverged from a common ancestor to modern lobsters more than 250 million years ago to live in freshwater environments as their brethren dispersed throughout the seas. A few years back, I studied Cretaceous crayfish and their burrows in Australia, but had never seen a live crayfish in its burrow here in Georgia, let alone seen so many of their tracks in one place. We even saw some crayfish (probably a species of Procambarus) poking their heads and claws out of their burrows, or walking around on the mudflat. So it turned out we did not need to go to the Georgia coast after all to see traces reminding us of Jordi: they had been right here with us the whole time.

A crayfish at its burrow entrance in the mudpit now in Decatur Cemetery, either defending its territory, or waving goodbye to people who study its kind and their traces. Your choice, but I know which one I’m picking.

In April, Jordi began writing about ichnology and invertebrate zoology for a more public audience through his cleverly titled blog, Infaunal Epiphany. His first entry was titled First Post, Hope Not Last!, in which he expressed a growing aspiration to connect with more than just his academic colleagues:

We scientists produce science. We scientists consume science. Most of us do that. We do our research, we publish it and other scientists read it. We are keeping all the fun for ourselves!!! It is true that there are scientists, journalists and writers who devote an effort to popularize science results. They are the ones building a bridge to society and I think it is fair to do that as many of us are investigating on public money.

Jordi wanted to share the fun of science, and in that respect, field trips with him were always a delight. These are probably what I will miss most about him, a pang that becomes particularly acute when I realize that one of our last conversations was about his some day visiting the Georgia coast to see its modern traces with me and our like-minded friends.

Lastly, in the light of his most recent life departing us, perhaps Jordi’s most poignant post on his nascent blog was Seven Reasons to Reincarnate as a Cephalopod. I won’t spoil it for anyone who hasn’t read this wonderful piece, but will just say that this post alone showcases how Jordi’s fine sense of humor blended readily with his science.

We will never know whether Jordi’s wish came true, let alone which cephalopod he might have become, or whether some element of his considerable spirit is now somehow connected to one of his beloved crustacean tracemakers or bioeroders in the past or present. But we can be assured that he will continue to live with us through his works and our memories of him. When our ichnological community meets again in his home town of Barcelona four years from now, his traces will all around us, continuing to inspire us to learn and live more.

Salud y un abrazo grande, mi amigo Jordi. Vaya con las trazas.

Correction: Someone pointed out to me that the newly elected International Ichnological Association (IIA) president is actually Alfred Uchman, not Jord. Jordi only seemed presidential to me because of his inspiring report given at Ichnia 2012 as outgoing secretary of the IIA and his agreement to host Ichnia 2016. (I am pleased to report that Alfred likewise gave an excellent speech to those gathered.) Apologies for the mistake, and thanks (as always) to anyone who points them out to me.

Out of One’s Depth in the Ediacaran

Posted on August 27, 2012 by TMartin

In my previous post, which followed a field trip to see a spectacular assemblage of 565-million-year-old Ediacaran body and trace fossils at Mistaken Point in Newfoundland, I made an awkward confession. This admission was that the stock phrase “the present is the key to the past,” used by geologists and paleontologists to describe actualism (also known as uniformitarianism) really depends on which past you’re talking about. As it turns out, when it comes to earth history, there are a lot of pasts.

Looking from afar onto the world standard for rocks recording the transition from life that lived superficially to life that, well, went a little deeper. (Photograph by Ruth Schowalter, taken at Fortune Head, Newfoundland (Canada).)

For instance, if you mean to apply that aphorism while referring to the last 12% of earth history, then for the most part you’ll be OK, although some of it will fall completely flat (more on that later).

But if you think it can be said blithely when referring to a time when all of the lifeforms looked like aliens from a bad Star Trek episode (TOS, of course), or when global oxygen levels were significantly lower than today, or the ozone layer protecting us from UV radiation was mostly absent, or deep-burrowing predators were completely unknown from every ecosystem, or the geochemistry of bottom sediments in the world oceans were radically different, then that’s not going to work so well for you. The world was vastly different at the Precambrian-Cambrian transition about 550 million years ago, and no amount of studying modern geological and biological processes or, say, modern traces of the Georgia barrier islands, is going to close that factual gap.

Underneath the intertidal sandflats of the Georgia barrier islands lurks the common moon snail (Neverita duplicata), detected through its burrow (left); and it radiates malevolence once exhumed from the burrow end (right, arrow). It is the top predator, the lion of the tidal flat, one might say, burrowing under sandflat surfaces to stalk its prey (other mollusks, including its own species), enveloping them with its muscular foot, and drilling into their shells to eat them alive. Simple, effective, and deadly. Was there anything like this moon snail in the Ediacaran Period, 635-542 million years ago? Nope. (Photographs by Anthony Martin, taken on Jekyll Island, Georgia.)

So let’s say you took a common moon snail from the Georgia coast and sent it back to the Ediacaran. You would think its evolutionarily advanced status, placed among such primitives, means that it would suddenly become the gastropod equivalent of a Terminator (the Summer Glau version, of course), wiping out every Ediacaran challenger in its mucus-lined path. Instead, it would die and quick and messy death from a combination of low oxygen levels, excessive biomats getting in its way, a lack of desirable prey, and excessive UV radiation. So you can stop building that gastropod-sized Tardis, and just face up to two realities: (1) the present is not always the key to the past; and (2) there is no such thing as time travel.

Oh yeah, back to the field trip. During the same excursion that included a stop at Mistaken Point, we also went to Fortune Head. Fortune Head is the place where the International Commission on Stratigraphy established the standard stratigraphic boundary for the switch from the Precambrian to the Cambrian. Called a Global Boundary Stratotype Section and Point (GSSP), or simply “stratotype,” this is a section of rock with the most nearly complete transition of rock units representing one time unit to the next.

A plaque at Fortune Head Ecological Reserve, informing visitors about the scientific importance of this site to geologists and paleontologists.

For example, the outcrop at Fortune Head is the stratotype for the transition from the Ediacaran Period (635-542 mya) to the Cambrian Period (542-488 mya). Sometimes geologists nickname this system of picking an exact boundary “the golden spike,” invoking images of a geologist hammering such a gaudy implement into the outcrop to imperiously announce its precise location. Lacking such geo-bling, though, we settled for one of the field trip leaders simply pointing with his walking stick to the boundary.

While we stayed safely on the hillside, the graduate students risked their lives to climb down onto the section and point at the Ediacaran-Cambrian boundary at Fortune Head, Newfoundland. For me, this brought back fond memories of Marlin Perkins, Jim Fowler, and Wild Kingdom. (Spoiler: the graduate students made it back OK.) (Photograph by Anthony Martin.)

So how would you know for yourself where, er, when you are – geologically speaking – in a section that has the youngest rocks of the Ediacaran Period and the oldest rocks of the Cambrian Period? That’s where the awesome power of ichnology comes into play, and it’s really simple to wield. If you look at the rocks and see the following trace fossil – Treptichnus pedum – you’re in the Cambrian Period. But if you don’t, you’re in the Ediacaran.

Whoa, check out that beautiful trace fossil! It’s Treptichnus pedum, a burrow made by a deposit-feeding animal, which was probably a worm-like animal, but also could have been an arthropod. Regardless of who made it, it’s a burrow reflecting a new behavior that evidently didn’t exist only a few million years before it was made. And that, boys and girls, makes this trace fossil a distinctive one. Scale in centimeters. (Photograph by Anthony Martin, taken at Grand Bank, Newfoundland.)

This trace fossil, a feeding burrow made by an invertebrate animal living in the seafloor 542 mya, is one of the few trace fossils used as an index fossil. Index fossils (also called guide fossils) tell you the age of the rocks you’re viewing. A good index fossil should have the following traits:

Abundant
Easily identifiable
Stratigraphically restricted
Geographically widespread

Treptichnus pedum indicates a behavior very different from every other trace fossil seen in Ediacaran rocks. It shows that the burrowing animal – probably a type of worm or arthropod – systematically probed into the sediment to ingest some of it, withdrew back into the main part of its burrow, then moved forward to probe again. Furthermore, over the course of making its burrow, its pathway may make loops, which increased the likelihood of it getting lots of goodies (organics) from the sediment. This behavior was totally different, and if it had been allowed to happen in the Ediacaran, no doubt would have led to laughter and ostracizing by other epifaunal and infaunal invertebrates. That is, if they could laugh or ostracize. (Hey, like I said, it was really different back then.)

But here’s the really strange dimension of the Ediacaran Period: as far as burrowers were concerned, it was mostly two-dimensional. Animal movement seemed restricted to horizontal planes, in which animals (worm-like or otherwise) squirmed, crawled, anchored and pulled, or whatever they did to get around, but stayed mainly in the plane.

Vertical movement, such as daring to burrow up or down in the sediment, was forbidden by either the rules of the marine ecosystems at that time, or by the bodies of the animals themselves. What kept animals from digging a little deeper? Part of the problem was that the seafloor was ruled by microbial mats, which covered sediment surfaces like plastic coverings on furniture at your grandma’s home.

This wrinkled surface on a Lower Cambrian sandstone just above the Ediacaran-Cambrian boundary at Fortune Head, Newfoundland is evidence of a probable microbial mat, or “biomat” These biomats were really common in the Ediacaran, became less common in the Cambrian, then after the Cambrian became more rare than a modest politician in an election year. Scale in centimeters. (Photograph by Anthony Martin.)

So if you were an animal then, you had no choice: you could adapt to being under these mats or on top of them. To make matters worse, all animal life apparently lacked the right hard parts, limbs, or other anatomical traits that could have pierced those mats or excavated the sediment underneath them. So no amount of rugged individualism in those invertebrates was going to change their horizontal movement to vertical.

A horizontal trail, probably made by an invertebrate animal, preserved on a 565-million-year-old bedding plane at Mistaken Point, Newfoundland. So you thought you could burrow vertically? Forget it, Jake – it’s Ediacaratown!

Of course, eventually the earth changed, the tyranny of the microbial mats was overcome by new evolutionary innovations in animals, and other adaptive paths took life into a third dimension. Consequently, the animals living on the seafloor started acting more like the ones we see today: not just living on or just underneath that seafloor, but also going down into it. This change was huge in an ecological sense, sometimes dubbed by paleontologists as the agronomic revolution, which accompanied the Cambrian explosion. This is not to say that revolutions must involve explosions, though. On the contrary, this was a quiet and slow sort of revolt, in which as earth environments changed, natural selection favored the burrowers, and the burrowers changed their environment. ¡Viva la revolución!

Here’s a little musical lesson about the increased biodiversity of the Cambrian Period. Professors, assign it to your students. Students, tell you professors about it, so they can look like they’re almost hip when they assign it. And for American viewers: the song has some sort of subversive subliminal message toward the end, praising some country other than the U.S. You’ve been warned.

In this respect, what was most meaningful about our visit to Fortune Head was seeing evidence of this ecological shift at the very same outcrop holding the stratotype for the Ediacaran-Cambrian boundary. Small, thin burrows preserved in the rocks from the earliest part of the Cambrian Period, spoke of this difference in the way life related to the seafloor. Vertically oriented they were, having gone into the sediment at a depth only the width of my fingernail. Nonetheless, it was a start, and an important one, heralding the evolution of ecosystems that more closely approach those of today.

See that little U-shaped burrow just below that thin sandstone? It only goes about a centimeter down, but that’s deeper than nearly any other burrow you would see in rocks from the Ediacaran Period. This sort of simple U-shaped burrow is given the ichnogenus name Arenicolites by ichnologists. Canadian-themed scale is in centimeters. (Photograph by Anthony Martin, taken at Fortune Head, Newfoundland.)

Same goes for this burrow, which is a spiral – cut on its side – and named Gyrolithes. Scale bar = 1 cm (0.4 in). (Photograph by Anthony Martin, taken at Fortune Head, Newfoundland.)

Life has moved further downward since, from worms to arthropods in marine environments, then later from millipedes to dinosaurs to gopher tortoises in continental environments, looking to places well below the surface that they could call home. So it was a awe-inspiring privilege to see a sample from the geologic record of when this first started, one centimeter at a time.

What was next stage for burrowing animals in the world’s oceans during the next 100 million years or so? To answer that question, we’ll jump ahead to the Ordovician Period, shuttling between rocks and trace fossils of that age in both Newfoundland and Georgia (USA, y’all). But while doing this, we’ll also look for glimpses of how these Ordovician trace fossils get just a little bit closer to the traces we being made in the modern sediments of the Georgia coast, and thus more like the actualism we all know and love.

Further Reading

Bottjer,D.J., Hagadorn, J.W., and Dornbos, S.Q. 2000. The Cambrian substrate revolution. GSA Today, 10(9): 1-7.

Canfield, D.E., and Farquhar, J. 2009. Animal evolution, bioturbation, and the sulfate concentration of the oceans. Proceedings of the National Academy of Sciences, 106: 8123-8127.

Gingras, M., et al. 2011. Possible evolution of mobile animals in association with microbial mats. Nature Geoscience, 4: 372-375.

Seilacher, A. 1999.Biomat-related lifestyles in the Precambrian. Palaios, 14: 86-93.

Vickers-Rich, P., and Komarower, P. (editors). 2007 The Rise and Fall of the Ediacaran Biota. Geological Society of London, Special Publication 286: 448 p.

Mistaken Point and the Limits of Actualism

Posted on August 23, 2012 by TMartin

Sometimes we paleontologists, especially those who also study modern organisms and their behaviors, get a little too sure of ourselves, thinking we have a clear vision of life during the pre-human past. So it’s good to have that confidence shaken a little, made uneasy by a glimpse at a much deeper past, one that preceded the bulk of fossils that shape our accepted norms and basic expectations in paleontology.

Welcome to the Ediacaran Period, the span of earth history from 635-542 million years ago, and a time when actualism – the precept that the present is the key to the past – becomes a naïve, idealistic dream, a glib summary of a world that has only existed for a mere 12% of earth history.

What are these? They’re fossils, but otherwise I’m not sure what else to tell you: guess I’ve been spending too much time in the present. But for for those people who have studied them and know better than me, they’re called Charniodiscus, and they’re frond-like fossils with holdfasts (those circular parts connected to their stems) that kept them attached to the seafloor about 565 million years ago. All you have to do to see these fossils is go to Newfoundland, Mistaken Point Ecological Reserve in Newfoundland, Canada, get permission from the Reserve to visit them, have a guide accompany you, and walk 40-45 minutes to the site from a car park. Incidentally, there will be absolutely no cafes or toilets on the way there. You know, just like how it was in the Precambrian. (Photograph by Anthony Martin; scale in centimeters.)

These discomforting realizations started a little less than two weeks ago, inspired by a field trip to the Ediacaran-Cambrian rocks of eastern Newfoundland, Canada. Why was I in cool, temperate Newfoundland, instead of sweating it out on the summertime Georgia coast? The occasion was a pre-meeting trip associated with the International Congress on Ichnology, simply known among ichnologists as Ichnia. This was the third such meeting, a once-every-four-years event (coinciding with years of the summer Olympics). The previous two were in Krakow, Poland (2008) and Trelew, Argentina (2004), and thus far these meetings also include fabulous field trips.

For Ichnia 2012, upon seeing an announcement of a field trip to Mistaken Point and other localities associated with the Precambrian-Cambrian boundary, I eagerly signed up for it. You see, Mistaken Point is world famous for its extraordinary preservation of more than 1,000 body fossils of those weird and wonderful fossils known as the Ediacaran fauna, Ediacaran biota, Vendian fauna, or Vendobionts (take your pick). This was the main reason why my fellow ichnologists on the field trip – 16 of us from 9 countries – were along for the ride, despite the trip’s clear emphasis on body fossils.

A rare photo of ichnologists getting really excited about seeing body fossils, which is totally understandable when we’re talking about the Ediacaran fossils at Mistaken Point, Newfoundland. Eventually, though, they later became unruly and started demanding, “Show me your trace fossils!” Fortunately for the sake of international ichnological relations, the field-trip leaders happily obliged that same day. (Photograph by Ruth Schowalter.)

These rare fossils, which are strange enough to even cause paleontologists to question whether or not they are animals (hence the cautious use of the more inclusive term “biota” instead of “fauna”), are abundantly exposed on broad bedding planes in Mistaken Point Ecological Reserve on the southeastern coast of Newfoundland. Discovered in 1967, these fossils have since proved to be one of the best examples of easily visible body fossils from more than 542 million years ago, and the Newfoundland fossils comprise the only such assemblage that originally lived in deep-marine environments. They evidently died in place when suffocated by a layer of volcanic ash that settled onto the seafloor, hence the fossils reflect a probable sample of their original ecosystem. This ash layer neatly preserved the fossils, and its minerals provided a means to calculate absolute age dates for the assemblage, which is from 565 +/- 3 mya (million years ago).

Bedding-plane exposure at Mistaken Point with many frond-like fossils, broadly referred to as rangeomorphs. (Photograph by Anthony Martin, Canadian-themed scale is in centimeters.)

A close-up of one of the more exquisitely preserved rangeomorphs, which I think is Fractofusus misrai. But you really shouldn’t trust this ichnologist with that identification, so it’d be wise to double-check that with a real expert. (Photograph by Anthony Martin.)

Just a few years ago, though, Mistaken Point became paleontologically famous again, and this time for its trace fossils. Researchers from Memorial University in Newfoundland and Oxford University looked at bedding planes near those holding the the body fossils, and were surprised to find a few trails there. At that time, it was the oldest evidence of animal movement from the fossil record, and although these finds have been disputed and others have tried to stake this claim for trace fossils elsewhere, it is still holding up fairly well.

A surface trail, probably made by a < 1 cm wide animal moving along the seafloor about 565 mya. The animal moved from left to right, which is indicated by the crescentic ridges inside the trail, which open in the direction of movement. (Photograph by Anthony Martin, taken at Mistaken Point, Newfoundland.)

Another surface trail, but this one without the internal structure of the other one, and with levees on either side of the central furrow. (Photograph by Anthony Martin, taken at Mistaken Point, Newfoundland.)What’s this? Don’t have a clue. It looks like a series of overlapping trails, some looping, but would have taken me several hours to unravel. Anyway, it generated some good discussion at the outcrop, and they’re probably trace fossils, which made us ichnologists both happy and perplexed. (Photograph by Anthony Martin, taken at Mistaken Point, Newfoundland; scale in centimeters.)

What made these trace fossils? It’s hard to say, and that’s a humbling statement for me to make. In public talks I’ve given about my upcoming book, and in a presentation I gave the following week at Ichnia on the Memorial University campus, I’ve assured how the actualism of the Georgia barrier islands and its traces can reliably serve as models for interpreting many trace fossils formed in different environments, and trace fossils of various geologic ages from around the world. But in this instance, I didn’t have a inkling of what made the Mistaken Point trace fossils. These trace fossils were also made in deep-marine environments, which are lacking from the Georgia coast, and I haven’t learned much about deep-marine trace fossils from elsewhere.

In short, my ignorance was showing, and these trace fossils were completely out of my realm of experience. The only feeble hypothesis I could conjure on the basis of what I’ve seen in modern sediments of the Georgia barrier islands are small marine gastropod trails. Sorry, that’s all I got.

Oooo, look, it’s snail! Making a trail! Isn’t that neat? And if you squint really hard and have a couple of beers, you might agree that it almost resembles one of the fossil trails from Mistaken Point. Don’t see it yet? Here, have another beer. (Photograph by Anthony Martin, taken at Sapelo Island, Georgia; scale in millimeters. )

But if ignorance loves company, I can feel good in knowing that others have grasped at the same straw of actualism and found it far too short. I could tell a few of my ichnological colleagues were likewise a little challenged by what they saw at Mistaken Point, and I knew that for some of them – like me – they normally deal with trace fossils in much younger rocks. But hey, that’s what geology field trips are supposed to do: challenge us with what’s really there in the rock record, right there in front of us, rather than what we wish were there.

Fortunately, a little more information provided during the meeting after the field trip helped my understanding of the trace fossils we saw at Mistaken Point, and actually connected to modern tracemakers. Alexander Liu, the primary author of the paper that first reported the trace fossils, gave a talk that reviewed the evidence for Precambrian trace fossils, including those from Mistaken Point. In experiments he and his coauthors did with living anemones in a laboratory setting, they were able to reproduce trails similar to the Mistaken Point trace fossil with the internal structure. Thus these researchers were able to use actualism to assist in their interpretation, which also meant that neoichnology was not so useless after all when applied to the Ediacaran. That made me feel a little better.

Let’s take a look at that first surface trail again, but this time with the help of my trustworthy colleague Paleontologist Barbie, who was along for the field trip. The crecentic ridges in the interior of the trail may represent marks where the basal disc of a anemone-like animal pushed against the surface as it moved. Even more interesting, the arrow points to an oval impression, which may be a resting trace that shows the approximate basal diameter of the tracemaker. What was the tracemaker? It’s currently identified as a small anemone, which is based on modern traces. Neoichnology rules! (Photograph by Anthony Martin.)

Ediacaran trace fossils still engender debate, though, and especially with people who don’t necessarily accept that animals made trails during the Ediacaran. For instance, about four years ago, some scuba-diving researchers observed a giant protozoan making a trail on a sediment surface in the Bahamas. Accordingly, they proposed that one-celled organisms – not animals – could have made similar trails during the Ediacaran Period. Interestingly, this shows how actualism can produce conflicting results when applied to Ediacaran fossils. After all, it’s still a big world out there, and we humans haven’t really observed everything in it yet.

So I’ll make one last point about Ediacaran fossils here, then will move on to more recent times. If you think that at the very least we paleontologists should be able to tell the difference between trace fossils and body fossils in Ediacaran rocks, you’re also in for some confusion. In the only research article I have ever attempted on Ediacaran fossils, which were much closer to Georgia – coming from the Carolina Slate Belt of North Carolina – my coauthors and I struggled with exactly that question with some fossils found in that area. In the end, we said they were body fossils, not trace fossils. And as everyone knows, I love trace fossils, and I really wanted these to be trace fossils. But they were not. That’s science for you: denying your deepest desires in the face of reality.

So surely the Cambrian would be easier to interpret, right? I meanl, after 542 mya, animals started burrowing merrily, to and fro, hither and tither, with uninhibited and orgiastic abandon, and, well, you get the idea. But, not really. Another part of the field trip involved looking at what happened with the departure of the relatively unbioturbated alien world of the Ediacaran, pre-542 mya, to the more familiar sediment mixing of the Cambrian and Ordovician Periods, post-542 mya. Yet even these rocks and their trace fossils were still not quite like what we see today.

This will be the subject of my next post, which will again explore the theme of how we should approach strict actualism like any scientifically based idea: with a mixture of astonished wonder, but also with a hard-edged look at what is really there.

As we bid adieu to Mistaken Point and began our walk back to the car park, we could swear we saw lifeforms emerging from the mist-covered rocks, resurrected from the deep time and deep water of the Avalonian Precambrian. Then we realized those were just some of our group behind us. Oh well. Maybe next time. (Photograph by Anthony Martin.)

(Acknowledgements: Much appreciation is extended to the field trip leaders – Liam Herringshaw, Jack Matthews, and Duncan McIlroy – for their organization and execution of a fantastic three-day field trip; to Valerie and Richard of the Mistaken Point Ecological Reserve for guiding us to the site; to my ichnological colleagues for their cheery and knowledge-broadening company; and my wife Ruth for being with me and providing an artist’s perspective about her experiences with us crazy ichnologists, shared here and here.)

Further Reading

Fedonkin, M., Vickers-Rich, P. Grey, K., and Narbonne, G. 2007.The Rise of Animals: Evolution and Diversification of the Animalia. Johns Hopkins Press, Washington: 320 p.

Liu, A.G., McIlroy, D., and Brasier, M.D. 2010. First evidence for locomotion in the Ediacaran biota from the 565Ma Mistaken Point Formation, Newfoundland. Geology, 38: 123-126.

Matz, M.V., Frank. T.M., Marshall, N.J., Widder, E.A., and Johnsen, S. 2008. Giant deep-sea protest produces bilaterian-like traces. Current Biology, 18: 1-6

Tacker, R.C., Martin, A.J., Weaver, P.G., and Lawver, D.R. 2010. Trace vs. body fossil: Oldhamia recta revisited. Precambrian Research, 178: 43-50.

Vickers-Rich, P., and Komarower, P. (editors). 2007 The Rise and Fall of the Ediacaran Biota. Geological Society of London, Special Publication 286: 448 p.

Deep in the Dinosaur Tracks of Texas

Posted on August 6, 2012 by TMartin

Given the continuing public mania over dinosaurs, and recent important discoveries of yet more exquisite specimens of feathered theropod dinosaurs discovered in countries far away from the U.S. (here and here), it is sometimes easy to forget what has long been known about these animals, and right here in my own “backyard” (globally speaking).

Need to see some of the best dinosaur tracks in the world, and you live in the southeastern U.S.? Guess what: you can seen them in Glen Rose, Texas. Not China, Mongolia, Canada, Utah, or some other far-off land inhabited by strange people with unusual customs, but Texas. Saddle up! (Photograph by Michael Blair, taken in Dinosaur Valley State Park, Texas.)

So on July 22, just to jog my memory a bit, I flew from Atlanta, Georgia to the Dallas-Ft. Worth (Texas) airport, and only a few hours later was gazing upon dinosaur tracks accompanied by the burrows of invertebrate animals, both trace fossils having been made more than 100 million years ago. It was a fitting welcome to Glen Rose, Texas, a place famous for its dinosaur trace fossils since the 1930s, and where dinosaurs were an integral part of its culture long before it was cool, hip, and contemporary elsewhere.

In Glen Rose, Texas, the dinosaur tracks are so abundant, you can choose whether to see these just outside of your hotel room, or go to the hotel jacuzzi and pool. Naturally, I chose both. (Photograph by Anthony Martin, taken in Glen Rose, Texas.)

So just how did I end up in Glen Rose, Texas, looking at Cretaceous dinosaur tracks and invertebrate burrows? I was lucky enough to be there as an invited participant in an expedition sponsored by the National Geographic Society. I say “lucky” because luck was certainly a part of it, a fortuitous connection made through my writing a book about the modern traces of the Georgia coast. James (Jim) Farlow, a paleontologist at Indiana-Purdue University Fort Wayne (IPFW) and an associate editor with Indiana University Press, reviewed the first draft of my book, but he was also in charge of this dinosaur-track expedition to Glen Rose. Evidently he was impressed enough about what I knew about invertebrate burrows (or at least what I wrote about them) that he considered me as a possible member for his team of scientists, field assistants, and teachers on this expedition.

Dr. Jim Farlow, the world expert on the Glen Rose dinosaur tracks, having a reflective moment at Dinosaur Valley State Park near Glen Rose, Texas. What’s with the broom? He and other people in the expedition used these to sweep river sediment out of dinosaur tracks submerged in the river. In 100° F (38° C) temperatures. On the other hand, I just described invertebrate trace fossils, which was more of a job, not work. (Photograph by Anthony Martin, taken in Dinosaur Valley State Park, Texas.)

Thus when Jim asked me last fall if I would be interested in joining them to describe and interpret the Cretaceous invertebrate burrows that occur with the dinosaur tracks there, I jumped at the opportunity. The Glen Rose dinosaur tracksites, most of which crop out in the Paluxy River bed in Dinosaur Valley State Park, are world famous for their quantity and quality, and they connect with an important part of the history of dinosaur studies. Going there, experiencing these tracks for myself, and better understanding their paleoecological and geological context would be of great benefit to me, my students, and of course, you, gentle readers.

Just to back up a bit, and clarify for anyone who doesn’t know why these tracks are so darned important, here’s a brief background. In November 1938, Roland T. Bird, an employee of the American Museum of Natural History and a field assistant to flamboyant paleontologist Barnum Brown (the guy who named Tyrannosaurus rex), saw large, isolated limestone slabs with theropod dinosaur tracks in a Native American trading post in Gallup, New Mexico. Upon inquiring about the origin of these tracks, Bird was told they came from Glen Rose, Texas. So he set out in his Buick for Glen Rose to see for himself whether these tracks were real or not, and whether there were any more to see in the rocks around Glen Rose. The theropod track set in the town bandstand – pictured below – was one of the first sites that greeted him, and Glen Rose locals told him about the tracks in the Paluxy River.

Glen Rose, Texas, the only place in the world where the town bandstand has an Early Cretaceous theropod dinosaur track on display. Wish I could also tell you about all of those little holes in the rock with that track, but I can’t right now. Nonetheless, rumor has it they are burrows made by small, marine invertebrates that lived at the same time as the dinosaurs. (Photograph by Anthony Martin, taken in Glen Rose, Texas.)

Bird had hit the jackpot, the motherlode, the bonanza, the surfeit, the, well, you get the point. Not only did the Paluxy River outcrops contain hundreds of theropod dinosaur tracks – many as continuous trackways – but also the first known evidence of sauropod dinosaur tracks.

A couple of beautifully preserved theropod tracks under shallow water in the Paluxy River. Note that the track at the bottom also has a partial metatarsal (“heel”) impression, and look closely for the digit I (“thumb”) imprint on the right. Scale is about 20 cm (8 in) long. (Photograph by Anthony Martin, taken in Dinosaur Valley State Park, Texas.)

Funny how those “potholes” in the limestone bedrock of the Paluxy River have oblong outlines and form regular alternating patterns, isn’t it? Well, them ain’t no potholes, y’all. They’re sauropod tracks, and were among the hundreds recognized as the first know =n such tracks from the geologic record. (Photograph by Anthony Martin, taken in Dinosaur Valley State Park, Texas.)

The discovery of sauropod tracks was as huge as the tracks. Up until then, sauropods were assumed to have been so large that they could not support their weights on land and spent most of their time in water bodies. These tracks said otherwise, that these sauropods were walking along mudflats along with the theropods. In short, the trace fossil evidence contradicted the assumed story about how these massive animals moved. After all, trace fossils are direct records of animal behavior, and if interpreted correctly, can tell paleontologists more about what an animal was doing on a given day than any amount of shells, bones, and yes, even feathers.

Sauropod tracks from the main tracksite in Dinosaur Valley State Park, Texas. The sauropod was moving away in this view, and the trackway pattern is a typical diagonal-walking one, right-left-right. In parts of this trackway, both the manus (front foot) and pes) rear foot registered, something Bird noticed in 1938, his observation accompanied by more than a little bit of excitement. (Photograph by Anthony Martin, taken in Dinosaur Valley State Park, Texas.)

The details preserved in these sauropod tracks are also astounding. Most sauropod tracks I have seen elsewhere, in Jurassic and Cretaceous rocks of the American West, Europe, and Western Australia, are only evident as large, rounded depressions that you would only know are tracks because they form diagonal-walking patterns. In contrast, the Glen Rose tracks include all five toe and claw impressions on the rear feet (pes) and full outlines of the front feet (manus). The original calcium-carbonate mud in the shoreline environments where the sauropods walked, similar to mudflats I’ve seen in the modern-day Bahamas, is what made this exquisite preservation possible. The mud had to be firm enough to preserve these specific details of the sauropods’ feet, but not so soft that the mud would collapse into the tracks after the sauropods extracted their feet.

Beautifully preserved tracks, manus (top) and pes (bottom). Note the five toe impressions in the pes, which along with its size confirms that these were made by a large sauropod. Meter stick for scale. (Photograph by Anthony Martin, taken in Dinosaur Valley State Park, Texas.)

One sauropod trackway, preserved with a theropod trackway paralleling and intersecting it, was actually quarried out of the river and taken to the American Museum. Once there, its pieces stay disassembled for years, before Bird helped with putting the puzzle pieces back together so that it could be used as part of a display there.

Archival video footage of Roland Bird and his field crew working on the dinosaur tracks in the Paluxy River near Glen Rose, Texas. More about this tracksite and its role in the history of dinosaur paleontology is ably conveyed by Brian Switek here.

Photos at the visitor’s center at Dinosaur Valley State Park, showing the sequence of clearing (left) and extraction (right) of the limestone bed containing the theropod and sauropod dinosaur tracks. (Photographs taken of the photographs, then enhanced, cropped, and placed side-by-side by Anthony Martin.)

A lasting trace today of Roland Bird and his field helpers from the 1940s, in which they took out a sauropod and theropod trackway from this place and transported it to New York City. (Photograph by Anthony Martin, taken in Dinosaur Valley State Park, Texas.)

Other than some of the best-preserved Early Cretaceous dinosaur tracks in the world, one other claim to fame for the Glen Rose area, and not such a proud one, is its attraction to evolution deniers, a few charlatans who used the tracks to promote what might be mildly termed as cockamamie ideas. You see, Glen Rose is also the site of the infamous “man tracks.” These tracks are preservational variants of theropod tracks that – through a combination of the theropods sinking into mud more than 100 million years ago and present-day erosion of the tracks in the Paluxy River – prompted some people to claim these were the tracks of biblical giants who were also contemporaries of the dinosaurs. (Perhaps this is as good of a time as any to start humming the theme music for The Flintstones.)

Rare documentary footage of humans and dinosaurs interacting with one another during the Early Cretaceous Period, or the Late Jurassic Period. Whatever. Note the inclusion of other seemingly anachronistic mammals, too, such as the saber-toothed felid Smilodon. Perhaps this footage could be included in the curriculum of some U.S. public schools, providing a formidable counter to the views of 75 Nobel laureate scientists. Then we’ll let the kids decide which is right.

I will not waste any further electrons or other forms of energy by continuing to flog this already thoroughly discredited notion, but instead will direct anyone interested to a thorough accounting of this debacle to some actual scholarship here, summarizing original research by Glen Kuban and others in the 1980s through now that have laid to rest such spurious notions. Speaking of Mr. Kuban, I was delighted to meet him for the first time during while in Glen Rose (we had corresponded a few times years ago). I was even more gratified to spend a few hours in the field with him, discussing the genuinely spectacular trace fossils there in Dinosaur Valley State Park with these directly in front of us. Again, I’m a lucky guy.

The expedition was scheduled in Glen Rose for three weeks during late July through early August, but with so many commitments for this summer, I could only carve out a week for myself there, from July 22-29. Fortunately, this was enough time for me to accomplish what was needed to do, while also having fun getting to know the rest of the expedition crew – teachers, artists, videographers, laborers – and enjoying wonderful discussions (and debates) with colleagues in the field. The people of Glen Rose were also exceedingly welcoming and accommodating to us: we felt like rock stars (get it – “rock”?), and were feted by local folks three nights in a row during the week I was there. Many thanks to these Glen Rose for the the exceptional hospitality they extended to our merry band of paleontologists, geologists, river sweepers, or what have you.

You can’t see it, but I’m standing in a sauropod dinosaur track, which is a little deeper than the rest of the river bed. You also can’t see the invertebrate burrows that are in the limestone bedrock, which is fine, because I can’t show them to you yet anyway. But be patient: you’ll learn about them some day. (Photograph by Martha Goings, taken in Dinosaur Valley State Park, Texas.)

I can’t yet say much more about what I did during that week, as all participants signed an agreement that National Geographic has exclusive rights to research-related information, photos, and video unless approved by them. But if you’re a little curious about the daily happenings of the expedition (which just ended last week), Ray Gildner maintained a blog that succinctly touched on all of the highlights, Glen Rose Dinosaur Track Expedition 2012.

Still, I can say, with great satisfaction, that I did successfully describe and interpret invertebrate trace fossils that were in the same rocks as the dinosaur tracks. Hopefully my colleagues and I will have figured out how these burrows related to environments inhabited by the dinosaurs that walked through what we now call Texas.

All in all, my lone week in the Lone Star State was a marvelously edifying and educational experience, one I’ll be happy to share with many future generations of students and all those interested in learning about the not-so-distant geologic past of the southeastern U.S.

Group photo from the Glen Rose Dinosaur Track Expedition 2012. Names of all participants can be found here, but in the meantime, just sit back and admire those Dinosaur World t-shirts everyone is wearing. (Photograph by James Whitcraft or Ray Gildner: they can fight over who actually took it. Although, the automatic timer on his camera took the photo, so maybe it should get credit instead.)

Further Reading

Bird, R.T. 1985. Bones for Barnum Brown: Adventures of a Dinosaur Hunter. Texas Christian University Ft. Worth, Texas: 225 p.

Farlow, J.O. 1993. The Dinosaurs of Dinosaur Valley State Park. Texas Parks and Wildlife Department, Austin, Texas: 30 p.

Jasinski, L.E. 2008. Dinosaur Highway: A History of Dinosaur Valley State Park. Texas Christian University, Ft. Worth, Texas: 212 p.

Kuban, G.J. 1989. Elongate Dinosaur Tracks. In Gillette, David D., and Martin G. Lockley (editors), Dinosaur Tracks and Traces, Cambridge University Press, Cambridge, U.K.: 57-72.

Pemberton, S.G., Gingras, M.K., and MacEachern, J.A. 2007. Edward Hitchcock and Roland Bird: Titans of Vertebrate Ichnology in North America. In Miller, William, III (editor), Trace Fossils: Concepts, Problems, Prospects. Elsevier, Amsterdam: 32-51.

Public Outreach via Ichnology: Traces for Kids

Posted on July 19, 2012 by TMartin

(This post is the second in a series discussing academic scientists and public outreach of their science, but with a focus on my recent experiences in using ichnology and paleontology for public outreach. The first of the series, introducing science outreach in general and some of its challenges for academic scientists, is here.)

One of the clichés of the environmentalism is to “think globally, act locally,” and the same principle applies well to public outreach done by scientists. For example, here in Atlanta, Georgia, I live near Fernbank Museum of Natural History. And by “near,” I mean I can ride my bicycle to it in 10-15 minutes from either home or my workplace at Emory University. Over my 20+ years in Atlanta, I’ve tried to cultivate a relationship with Fernbank, having done some informal consulting for them on exhibits, given public lectures about my research in ichnology and paleontology, shown some of my science-based artwork there, and otherwise done volunteer work that qualifies as public outreach.

Look, a real paleontologist who somehow escaped from his “ivory tower” (or stone house) and found time to talk with the public! This is a small visual sample of the fun I had this past Saturday at Fernbank Museum of Natural History, talking with children and their parents about dinosaur trace fossils. Why yes, those are Paleontologist Barbies (one of them quite famous) sitting in the box to the right of me. Do you have a problem with that? (Photograph by Ruth Schowalter.)

But one of my acknowledged deficiencies in public outreach with Fernbank and elsewhere has been sharing my science with kids. Full confession: I don’t have children. (As far as I know, that is. If I ever run for political office, I’ll find out for sure.) Moreover, nearly all of the students I teach are 18 to 22 years old, and I normally don’t have children around me through family, friends, or neighbors in everyday life. Thus most of my experience in communicating science at any level is with adults. This leaves me feeling a little handicapped and less confident about my abilities to adapt and use the unique set of skills needed for relating sometimes-complex scientific concepts to children.

Why should I bother getting bothered about this, especially in doing outeach with a local natural history museum? Well, a simple reality of natural history museums today is that their economic survival relies on children visiting them, and preferably (although not necessarily) with their parents in tow. Sure, educating the young has always been a role of natural history museums. But pitching science solely to kids while bypassing adults has become so pronounced in some museums that adults have begun complaining about the “infantilization” of museum exhibits.

Fernbank is not immune to this charge. For example, the traveling exhibit they have there now – The Scoop on Poop – is clearly aimed at viewers 10 years old and younger, and is inspired by a children’s book with the same title. To be fair, though, Fernbank hosting the Darwin exhibit from the American Museum of Natural History last year was a refreshing concession to adults who certainly felt like kids, filled with excitement and awe, while learning about the roots of evolutionary theory.

A study in contrasts of traveling exhibits that have been to Fernbank Museum. Above, here’s part of the sign that greeted visitors to the Darwin exhibit, shown there September-December 2011…

…and here’s the sign welcoming people to the Scoop on Poop exhibit, showing there now. Gee, do you think each was intended for a different audience?

So it was with a mixture of mild trepidation, but also eagerness, that I welcomed an opportunity for outreach with kids and their parents last Saturday, July 14. One of my friends who works at Fernbank asked me several weeks ago if I’d be interested in participating in a museum event they organized for July 14-15, called “The Scoop on Dinosaurs.” In this event, Fernbank put together a range of dinosaur- and other science-related activities and programs for kids, but of course also designed it with the assumption that these kids would be accompanied by parents or other adults. The problem was, all of the planned activities lacked a real, practicing scientist, let alone a paleontologist. And seeing that I’m one of the few paleontologists in the Atlanta area, I live close by, and I enjoy doing public outreach, it made sense for me to participate.

After discussing it with my Fernbank friend, we decided that a simple “meet the paleontologist” format would work best, with me sitting at a table and talking informally with people about one of my research topics – dinosaur trace fossils – as they dropped by. I also thought it would be good to have a few props, and ones that would provoke inquiry-based learning, or what educators used to call “thinking.”

For example, I brought with me two sets of dinosaur bones, one of which was noticeably denser than the other. (And by the way, real bones are essential, so the kids could say and remember when they held real dinosaur bones.) These differences, which engaged a sense other than sight, lent well to the question, “Why is one bone heavier than the other, even though they’re the same size?,” followed by a discussion of the preservation of dinosaur bones.

Whoa, dinosaur bones! The darker dinosaur bone on the left is noticeably heavier than the lighter-colored one on the right, which the kids could feel for themselves right away when they put one in each hand. After they noticed this, I asked them why, and next thing you knew, we were having a scientific discussion.

Of course, because I’m ichnologist, you just knew some traces and trace fossils were somehow going to be involved in this, too. Sure enough, my friends at Fernbank printed out and laminated the following two photographs of mine, which I used to introduce the concept of dinosaur tracks to the kids. But rather than just blabbing on about each track, I showed them the photos and asked “Which one is the dinosaur track, which one is the bird track?” One track was from a modern sandhill crane (Grus canadensis) made on a Georgia barrier island, whereas the other was from a non-avian Cretaceous theropod dinosaur.

Which is the bird track and which is the dinosaur track? It’s kind of a trick question, but one that also introduces the concept that questions can have multiple right answers, and those answers lead to more questions and deeper meaning. And just in case you were wondering, the track on the left is from a theropod dinosaur, preserved in Early Cretaceous rocks that are about 105 million years old, and the one on the right is from a modern sandhill crane. (Both photographs by Anthony Martin, the left one taken in Victoria, Australia, and right one taken on St. Catherines Island, Georgia.)

For the more shy kids, I asked them to just point to the one they thought was the dinosaur track, and assured them that it was OK to be wrong, because being wrong is also part of science. So what was fun about this exercise was how they could be right no matter which they picked. If they pointed to dinosaur track, I would tell them they were right. But if they instead pointed to the modern sandhill crane track, I smiled and said, “You’re right, but it’s from a modern dinosaur, because birds are dinosaurs, too.”

This revelation led to a short explanation of how some dinosaurs are still around as birds, even if all of the other dinosaurs went extinct 65 million years ago. (Most of the kids already knew this, but I’m not so sure all of their parents did.) They also could clearly see that the tracks, which were very similar in size and shape, comprised one piece of evidence showing the relatedness of these two animals, even though they were separated by more than 100 million years. With a few of the older kids, we even talked some about how they were able to distinguish the fossil track from the modern one. (“That looks like a rock, and that looks like sand,” some of them said. Couldn’t have said it better myself.) What was really fun about this approach was to see how much the kids’ parents learned from this ichnologically based exercise, too. In other words, this wasn’t just done with children in mind.

Another simple trace-fossil-oriented quiz came from a photo of a 75-million-year-old dinosaur coprolite. Only I didn’t tell them it was a coprolite; instead, I told them what was in it (bits and pieces of plants), that my hand was in the picture (showing the size of the rock), and that the rock was a type of dinosaur trace fossil.

What’s this? It has bits and pieces of plants in it, it’s big (there’s my hand for scale), and it came from a dinosaur. If you said “paleo-puke,” that’s not bad, but you’re thinking of the wrong end of the dinosaur. It’s a coprolite, probably from a hadrosaur (like Maisaura), and is from the Late Cretaceous Two Medicine Formation of northwestern Montana.

With just those few clues, sometimes aided by my holding my nose, some kids actually figured it out (“DINOSAUR POOP!”), and even those who didn’t immediately get it were delighted with their answer after guiding them with just a few more questions. There’s probably something about their having recently learned proper toilet habits (reinforced daily) that makes feces loom large in a child’s imagination. So linking such traces to dinosaurs makes those feces even bigger, smellier, and hence more memorable.

With regard to other academic paleontologists who do public outreach, several parents mentioned that their kids regularly watch the TV show Dinosaur Train on PBS, and that’s how their children were learning about paleontology (or, more narrowly, just dinosaurs and pterosaurs). Although I’ve only seen a few clips from this show, I knew its host is also a real, academically trained research paleontologist with a Ph.D., Dr. Scott Sampson, sometimes known simply by the kids as “Dr. Scott.” So I made sure to tell these parents how fantastic it was to see an academic paleontologist with such credentials teaching paleontology in a children’s show. In other words, I was trying to counter the “Sagan effect,” while helping to dissuade parents from the notion that academic scientists are all disengaged from the public. (Maybe we paleontologists could call it the “Sampson effect.”)

Dr. Scott Sampson, an academic paleontologist who went on to do something a little different in his career, which was to become a science communicator with a recent focus on teaching paleontology to kids. Yet he still does peer-reviewed research on dinosaurs, meaning the two are not mutually exclusive. And you know what? The rest of us academic paleontologists think that’s cool.

Of course, I had lots of kids say, “I want to be a paleontologist!” Not wanting to crush their dreams with tales of pessimistic woe from academia (see my previous post if you need a big downer on that), I instead saw this as a chance for them to learn science in upcoming years, regardless of whether they become paleontologists or not. So advice I gave to those kids included (in particular order):

Get outside as much as possible. Although I’m not an overly fervent acolyte of Richard Louv and his “get kids in nature” movement, I do agree with the basic premise that kids need to connect more directly with nature by simply getting their little butts outside. From what I understand, “Dr. Scott” preaches the same message, so it’s good for kids to hear this coming from paleontologists, who do lots of their best work outside.
When you’re not outside, read as much as possible. Although, now that I think about it, I should have advised them to read outside.
Take lots of math classes. These kids represent the future, and the future of paleontology means more computer applications and more quantification of our data. So they can’t think about doing paleontology without also thinking about how math will be used in that science. Even though some kids wrinkled their tiny noses at me when I said “lots of math,” they got the message.
Take lots of science classes. And for the science classes, I told them that they’d better take geology, but also biology and chemistry. (I’m not sure if I mentioned physics, but maybe that was my way of getting back at fictional physicist Sheldon Cooper for what he’s said about geology.)

Yes, I know, all of this sounds wonderful, in a self-congratulatory, back-patting sort of way. Yay me! Nonetheless, while doing this outreach, I remained conscious of how I also fulfill a tenacious stereotype in paleontology. This typecasting has been discussed by fellow paleo-bloggers Victoria Arbour (here) and Brian Switek, the latter dubbing it the “male and pale” syndrome. It’s a syndrome exemplified by documentary filmmakers who pretend that the entire paleontological community is composed of middle-aged men of European descent, or, to throw in some diversity, older men of European descent.

Considering I live in an ethnically diverse place – Atlanta is more than 50% African-American, for starters – I’m reminded daily that my face doesn’t match those of most kids around me (and it’s not just the beard). This was certainly true for those kids and parents who stopped by to see me on Saturday: it was a rainbow of ethnicities totally unlike anything I experienced as a kid growing up in Indiana in the 1960s. But for here in Atlanta and many major metropolitan areas in the U.S. and around the world, this is normal. So if paleontologists who look like me plan to do public outreach, they have to be mindful of this reality, get educated about other ethnicities, and adjust accordingly. In this respect, I’ve been enlightened through working some with Emory’s Center for Science Education, which has had great success in implementing a variety of programs working to increase minority participation at all levels in STEM (science, technology, engineering, math) in the Atlanta area.

I’m also sensitive to the gender gap in perceptions of paleontologists, or the expectation that all paleontologists will be male, even as the demographics in our profession start to approach equity (though admittedly, we still have a long ways to go). So I made sure, after showing them the photo I had taken of a dinosaur coprolite from Montana and discussing how feces get fossilized, to tell them that the paleontologist who actually studied those coprolites was Dr. Karen Chin. Plus, I pointed toward the nearby Scoop on Poop exhibit and said they should go in there and watch Dr. Chin speak about her research on coprolites in several videos there. (Karen, if you’re reading this, thanks for your virtual help in being a cool role model!)

Dr. Karen Chin, the acknowledged world expert on dinosaur coprolites, who also doesn’t look like me (and that’s a good thing for both of us.) Here she is holding up one of her research subjects, which fortunately is sufficiently fossilized for her to gesture without getting any of it on her or the person behind the camera. Oh, and sorry if my photo taken from a video in The Scoop on Poop exhibit violates some sort of copyright, but I did it for the children. So there.

So it was with great joy and satisfaction that I’ll note my mere two hours of public outreach filled me with hope for the future. Many kids, accompanied by proud parents, stopped by to meet a “real paleontologist” and chat about, well, paleontology. Although I should have taken data, tabulated results, and analyzed them for significance, of the kids who said, “I want to be a paleontologist,” I recall the gender ratios were about 50:50. Probably my favorite brother-sister pair consisted of the brother who wants to be a paleontologist and the sister wants to be a marine biologist. (Making it even better, their dad was very pleased with the prospect of having two scientists in the family.)

I was also occasionally astonished at how knowledgeable some of the kids were. For example, one 10-year-old girl asked me whether one of the dinosaur bones I had brought was from a hadrosaurine or lambeosaurine dinosaur, which we then discussed (based on the extremely scanty evidence, that is). Her mother wore a face-splitting grin as she watched this exchange between her daughter and me, and other kids stood by in awe: looking at the girl, not me. Now that’s peer teaching!

Her (left): “What? You really think the phylogenetic distinction between the hadrosaur clades is based on THAT plesiomorphy?” Her sister (right): “Yeah, who taught you cladistics anyway?” Me: “Um, uh, OK. Say, have either of you ever watched Dinosaur Train?”

Will I do this kind of public outreach again? Sure, and Fernbank can certainly count on me doing more such programs with them in the future. From this experience I also learned that “dinosaurs and kids” as a frame for science education, whether at natural history museums or elsewhere, is a fountain that apparently never goes dry. But even better, I can still use my academic research specialty – ichnology – to provide a different perspective on dinosaurs specifically and science in general, for children and parents alike.

Public outreach in paleontology with kids can be fun and rewarding, given the right setting, preparation, and attitude. Meanwhile, just behind me, Gigantosaurus is apparently chasing Argentinosaurus, giving a whole new twist to the term “ankle biter.” (Photograph by Ruth Schowalter, taken at Fernbank Museum in Atlanta, Georgia.)

Further Reading

None for now. Go outside instead.

Public Outreach via Ichnology: The Prelude

Posted on July 18, 2012 by TMartin

One of the more popular topics discussed nowadays by scientists and science writers via online social media and meetings regards how academic scientists – you know, those Ph.D. types who live in Ivory Towers – might most effectively conduct public outreach. Public outreach is also known as public engagement, or (my favorite) “engaged scholarship,” a term that stops just short of sheepishly admitting that most mainstream academic scholarship at universities is disengaged from the public. This allusion is connected to a consensus that academic scientists don’t do enough public outreach, causing people to nod their heads knowingly in agreement, even though this idea normally lacks, like, you know, actual data. (One exception is here, though.)

Wow, look a real paleontologist! Or maybe it’s a clever use of animatronics, or a holographic projection simulating a paleontologist, because everyone knows university scientists never go out to meet the public. (Photograph by Ruth Schowalter, taken at Fernbank Museum of Natural History in Atlanta, Georgia.)

Regardless of whether academic scientists are disengaged, engaged, or simply eloping with people outside of their peer groups, at least part of the discussion revolves around how academics can be rewarded for their outreach. The conventional wisdom nowadays I read and hear about university scientists is that:

They are terrible at communicating their science to laypeople, so everyone is better off if they just stay in their labs or in the field and not even try to talk with anyone other than their few (and I mean, very few) geeky friends.
They will not be rewarded for doing outreach, unless it’s required by the granting agency that gave them whatever research grant they have at the time (grant blackmailing, you might say).
They are actively discouraged from doing outreach, even if they’re already doing it through blogging, public presentations, making informative videos, working with science educators and science journalists, and so on.

With regard to the last of these, the negative consequence of outreach has been sometimes nicknamed the “Sagan Effect” (yes, that Sagan), in which non-outreaching scientists – arms crossed against their chests – may shun, poop-poo, or otherwise denigrate those scientists who dare to talk to the public. This basal primate behavior stems from the perception that scientists who are guilty of such slumming, including their writing books for non-colleagues, talking to journalists, and appearing on TV, must not be very good or very serious scientists (the latter being a far harsher judgement). And despite evidence to the contrary, this prejudice seemingly lingers.

Fortunately, my personal sense and one shared by many in the online science-loving community is that the tide has turned on this pernicious attitude. This shift is partly because most of those in academia who think “scientists who also try to be communicators = scum” are retiring, dying, or otherwise removing themselves from the meme pool, and their ranks are being filled incrementally by people who embrace public outreach. In other words, even ivory towers can evolve, especially if the next generation, schooled by people like Carl Sagan, pass on their memes.

Did you know that one of the best and most well-known science communicators – Bill Nye the Science Guy – does not have a Ph.D. in science and has never been a research scientist at a university? He “only” has a B.S. degree in mechanical engineering from Cornell University and some honorary degrees. Yet here he is, explaining natural selection (a basic principle of evolutionary theory) and connecting it to human alterations of environments, all while employing a masterfully mesmerizing blend of enthusiasm and ferocity that makes most of us Ph.D. types look like milquetoast. Or Wonder Bread. Or Miller Lite. Or some other grain-based metaphor that means really bland and boring. And he did it in less than two minutes. Oh, and did you know that one of his professors at Cornell was research scientist and science communicator Carl Sagan? That’s probably not a coincidence, just like the use of this video as an allegory for what’s happening to academic scientists in the U.S. right now.

Impediments also revolve around the discernment by scientists in the U.S. that most people may not be interested in what scientists have to say, regardless of what they have to say and how well they say it. I mean, when the U.S. National Oceanic and Atmospheric Association (NOAA) has to put out an official statement denying the existence of mermaids, it’s going to be an uphill battle no matter how enthusiastic and knowledgeable a scientist might be. Incidentally, as an ichnologist, I can independently verify that NOAA is very likely correct: thus far, I have not seen a single mermaid trace on any Georgia beach or elsewhere in the world. Although that would make for a good April Fool’s post next year. (You’ve been warned.)

Actual photographic evidence of the existence of mermaids. In your face, NOAA! But what intrigues me here is the distinctive ichnological evidence resulting from the resting trace of a extant half-piscine-half-hominin tracemaker in a sandy intertidal environment, and how to assess the fossilization potential of such evidence. (Photograph originally from the documentary film Splash, with many copies available all over The Internets.)

Related to this problem, though, is that the dream of young, academically trained scientists to become tenured research-oriented scientists in the U.S., who will then have little or no contact with people outside of their research group, is turning into a quaint anachronism. For one, anybody who has been following trends in U.S. universities knows that tenure-track positions in scientific fields are shrinking, especially as university budgets continue to tighten, salaries stagnate, and faculty support lessens. In other words, tenure-track positions are already alternative careers, not the norm.

This means that more people being trained as research scientists at those universities should expect to seek out or carve out their own careers in capacities other than those as traditional research scientists. One of these roles, of course, could be as scientists who communicate science to the public. Even so, scientists who wish to become science communicators with a public presence may not be rewarded for doing this in non-tenure-track positions at universities, or given enough time, as they will be teaching more classes and students. This means they may have to find other creative ways to channel their scientific knowledge while also earning a living wage. Not to mention health insurance, life insurance, retirement funds, and other mundane perks – ones we assumed that came with all of the hard work behind earning a Ph.D. in a scientific field – that are also in danger of diminishing in academia.

Wow, those are some broad-sweeping problems that require lots more discussion and some serious solutions! So what better way to do that than with personal anecdotes expressed through a blog and using my research specialty of ichnology? Stay tuned for that part tomorrow, Act I in Public Outreach via Ichnology, a mini-series based on a variety of real-life public-outreach encounters I’ve had as an academic paleontologist during the past week. And just to summarize what happened, while also foreshadowing: it was fun, real, and real fun.

How were these two photos of traces used to conduct public outreach of science with children at a natural history museum? If you want to find out, I guess you’ll have to read my next post.

Further Reading

Ecklund, E.H., James, S.A., and Lincoln, A.E. 2012. How academic biologists and physicists view science outreach. PLoS ONE, 7(5): e36240. doi:10.1371/journal.pone.0036240.

Mason, M.A. 2012. The Future of the Ph.D. Chronicle of Higher Education, May 12, 2012.

Marine Moles and Mistakes in Science

Posted on June 25, 2012 by TMartin

A first day of field work in the natural sciences can be expected to hold surprises, no matter what type of science is being attempted. Sometimes these are unpleasant ones, such as finding out the fuel gauge in your field vehicle – which you are driving for the first time, and in a remote place – doesn’t work. Other times, you make a fantastic discovery, like a new species of spider, a previously undocumented invasive plant, or a fossil footprint. But sometimes you see something that just makes you scratch your head and say, “What the heck is that?”, or more profane variations on that sentiment.

What is this long, meandering ridge making its way through a beach to the high tide mark on Sapelo Island, Georgia, and what made it? If you’re curious, please read on. But if you already know what it is, then you know a lot more than I did the first time I saw something like this. (Photograph by Anthony Martin.)

The last of those three scenarios happened to me on Sapelo Island, Georgia, in June 2004. My wife Ruth was with me, and we had just arrived on the island the previous afternoon, having stayed overnight at the University of Georgia (Athens) Marine Institute, or UGAMI. We decided that our first full morning in the field would be at Nannygoat Beach on the south end of Sapelo, which is a 5-minute drive or a 20-minute walk from the UGAMI.

We drove a field vehicle there (the gas gauge and everything else worked), parked, and took the boardwalk over the coastal dunes. Our elevated view from the boardwalk afforded a good look at many insect, ghost crab, bird, and mammal tracks made in the early morning. Circular holes punctured the dunes, made by ghost crabs (Ocypode quadrata). Sand aprons composed of still-moist sand were next to these burrow entrances, bearing crisply defined ghost-crab tracks, although early-morning sea breezes had already started to blur these.

At some point after walking onto the beach, though, we saw traces that we had not noticed in previous visits to Sapelo, and ones I have rarely seen there or on other Georgia barrier islands since. These oddities were meters-long, slightly sinuous to meandering ridges, about 15-20 cm (6-8 in) wide, extending in the sandy areas from the dunes through the berm and down to the high-tide mark, where they ended abruptly.

Same meandering ridge shown in the first photo, but viewed from the high-tide mark, showing how it connects with the primary dunes. Note how a few holes are punched in the part near me: more about those soon. (Photograph by Anthony Martin, taken on Sapelo Island, Georgia. P.S.: My wife Ruth is the scale in both photos, fulfilling one of the top 10 signs that I might be a geologist.)

Although a few ridges crossed one another, they rarely branched, and if they did, the branches were quite short, only about 10-15 cm (4-6 in). When we followed them to the dunes, they seemed to originate from some unseen place below the sandy surfaces. We investigated further by cutting through some of the ridges to see what they looked like inside. They turned out to be mostly open tunnels with circular cross sections about 5 cm (2 in) wide, slightly wider than a U.S. dollar coin. They were mostly hollow, and only occasionally did we encounter a plug of sand interrupting tunnel interiors. This supposition was backed up by ridges that had collapsed into underlying voids. A few of the ridges stopped with a rounded end the same diameter as the ridge, or as a larger, raised, elliptically shaped “hill.”

Ridge with quite a bit of meander in it. Check out the short branch toward the top right, where the tracemaker must have changed its mind and backed up, then continued digging toward the viewer. Scale = 15 cm (6 in). (Photograph by Anthony Martin, taken on Sapelo Island, Georgia.)

Two separate ridges intersecting, caused by one crossing the other, resulting in “false branching.” Also notice the partial collapse of sand into underlying hollow tunnels and how one of the ridges ends in a rounded mound. Scale = 15 cm (6 in). (Photograph by Anthony Martin, taken on Sapelo Island, Georgia.)

A short ridge ending in a raised, elliptical “hill,” connected to a partially collapsed tunnel that is not otherwise evident as an elevated surface. Same scale as before. (Photograph by Anthony Martin, taken on Sapelo Island, Georgia.)

Ruth and I agreed that these tunnels were burrows, instead of some random features made by the winds, tides, or waves. But by what? Clearly their makers were impressive burrowers, capable of digging through meters of sand. Their bodies also were probably just a little narrower than the burrow interiors, which helped us to think about body sizes. Then we considered where we were – dunes and beach – and what animals were the most likely ones to burrow in these environments.

A process of elimination – determining what they were not – was a good way to start figuring out their potential makers. For example, no way these burrows were from insects, such as beetle larvae, ant lion larvae, or mole crickets, because they were just too big. Insects also have a tough time handling salinity, so once they got to the surf zone with its saturated, saline sand, they would have had problems, or (more likely) an aversive reaction and turned around immediately instead of plowing ahead.

Insect burrow in coastal dune sand, made by a small beetle. Look at both the form and scale, and you’ll see this is not a match for what we were seeing. Scale in centimeters. (Photograph by Anthony Martin, taken on Cumberland Island, Georgia.)

Small mammals, like beach mice (Peromyscus polionotus), didn’t seem like good candidates either. Beach-mouse burrows are totally different from what we were seeing, and their burrows do not run all of the way down to the intertidal zone. Mice, like insects, also don’t like marine-flavored water; even if they might be able to temporarily tolerate it, they wouldn’t continue to burrow through moist, salty sand.

A beach-mouse burrow, with their tracks coming and going. Either the mice dug this burrow, or they occupied an abandoned ghost-crab burrow. Regardless, this also doesn’t match our mystery traces. Scale in millimeters. (Photograph by Anthony Martin, taken on Little St. Simons Island, Georgia.)

This led to an initial hypothesis that these burrows were from one of the most common larger burrowing animals in the area, and one comfortable in dune, berm, and beach environments with saturated, salty sand. These could only be from ghost crabs, I thought, an explanation supported by undoubted ghost crab burrows that perfectly intersected these tunnels, accompanied by undoubted ghost-crab tracks.

Ghost-crab burrows intersecting tunnels, accompanied by lots of ghost-crab tracks. Wow, that’s really convincing circumstantial evidence, wouldn’t you say? (Photograph by Anthony Martin, taken on Sapelo Island, Georgia.)

End of story, right? Well, no. I and a lot of other scientists have said this before, but it bears repeating: part of how science works is that in its practice we do not prove, we disprove. I somehow knew the “ghost crab burrowing horizontally through meters of sand from the dunes to the beach” hypothesis was a shaky one, and it bothered me that it just didn’t seem right. So I started reading as much as possible about ghost-crab burrowing behaviors. I thought I already knew a lot about this subject, but nonetheless was willing to acknowledge that there might be some holes in my learning (get it – holes?) that needed filling (get it – filling? Oh, never mind).

The gentle reader probably surmised what happened next. That’s right: not a single peer-reviewed reference mentioned ghost crabs digging meters-long shallow tunnels from the dunes to the beach. So either I was wrong, or I had documented a previously unknown and spectacular tracemaking behavior in this very well-studied species. A single cut by Occam’s Razor simply said, “You’re wrong.”

You thought I made long horizontal burrows that go all of the way from the dunes to the surf zone? Wow, you primates are dumber than I thought. (Photograph by Anthony Martin, taken on Sapelo Island, Georgia.)

If not a ghost crab then, what else could make meters-long horizontal burrows of the diameter we had seen? This is when I began to reconsider my original rejection of moles as possible tracemakers.

So what am I: chopped liver? (Photograph from Kenneth Catania, Vanderbilt University, and taken from Wikipedia.org here.)

Here’s what was the most interesting about this mistaken interpretation: it was made because of where we were. In other words, our initial mystification about these traces stemmed from their environmental context. Had we seen these burrows winding down a sandy road in the middle of a maritime forest on Sapelo Island, we would not have hesitated to say the word “mole.” Yet because we saw exactly the same types of burrows in coastal dunes and beaches, we said, “something else.”

A long, meandering mole burrow in the sandy road going through a maritime forest on the north end of Sapelo Island. So if you see a burrow like this in the forest, you instantly say “mole.” But if you see it on the beach, you say, “Um, uh, duh…must be something else!” My tracks (size 8 1/2, mens) and 15 cm (6 in) photo scale for, well, scale. (Photograph by Anthony Martin.)

Another long, meandering ridge ended in a rounded “hill,” a trace that no one would hesitate to call a mole burrow, especially because it’s in the middle of a maritime forest. (Photo by Anthony Martin, taken on Sapelo Island, Georgia.)

A trip back to the literature further confirmed the mole hypothesis while also serving up a big slice of humble pie. I was embarrassed to find that these same burrows were described and interpreted as mole burrows in an article published in 1986. Even more mortifying: my dissertation advisor (Robert “Bob” Frey) was the first author on the article; it had been published while I was doing my dissertation work with him; and I had read the article years ago, but didn’t remember the part about mole traces. It was like these burrows were saying to me, “Go back to school, young man.”

OK, so these are mole burrows. Case closed. Now that we’ve identified them, we can stop thinking about them, and go on to name something else. But that ain’t science either, is it? This one answer – mole burrows – actually inspires a lot of other questions about them, which could lead to heaps more science:

• Which moles made these burrows? The Georgia barrier islands have two documented species of moles, the eastern mole (Scalopus aquaticus) and star-nosed mole (Condylura cristata). Of these two, eastern moles are relatively common on island interiors, whereas star-nosed moles are either rare or locally extinct from some of the islands. But star-nosed moles are also more comfortable next to water bodies and seek underwater prey. So could these traces actually signal the presence of star-nosed moles in dune and beach environments? Frey and his co-author, George Pemberton, originally interpreted these as eastern mole burrows, but they also didn’t eliminate the possibility of star-nosed moles as the tracemakers, either.

• What is the evolutionary history of moles on the Georgia barrier islands? Are these moles descended from populations isolated from mainland ones 10,000 years ago by the post-Pleistocene sea-level rise, or do they represent more modern stock that somehow made its way to the islands? A genetic study would probably resolve this issue, but who the heck is going to compare the genetic relatedness of moles from the Georgia barrier islands to those on the mainland?

• What were they eating? Moles don’t just burrow for the exercise, but for the food. While burrowing, they are also voraciously chowing down on any invertebrate they encounter in the subsurface. But what would they eat in beach sands? As many shorebirds know, Georgia beaches are full of yummy amphipods, which would likely more than substitute for a mole’s typical earthworm- and insect-filled diet in terrestrial environments. Yet as far as I can find in the scientific literature, no one has documented mole stomach contents or scat from coastal environments to test whether these small crustaceans are their main prey or not.

• What happened to these moles once their burrows got to the surf zone? Did they turn around and burrow back, or did they go for a swim in the open ocean? The latter is actually not so far fetched, as moles are excellent swimmers, especially star-nosed moles. But how often would they do this?

• Just how common (or rare) are these burrows in beaches? Just because I just perceive these burrows as rare could be an example of sample bias. Yes, I wrote an entire book about Georgia-coast traces and tracemakers and have done field work on the islands since 1998. But I don’t live on the Georgia barrier islands, nor have I spent more than a week continuously on any of them. Keenly observant naturalists who live on the islands or otherwise spend much time there could better answer this question than me. I suspect they’re actually much more common than I originally supposed, and now look for them to photograph or otherwise document whenever I go back to any of the islands.

• Would such burrows preserve in the geologic record? Probably so, especially if they were made in dunes and filled with a differently colored or textured sand. But I’ll bet that nearly every paleontologist or geologist would make the same mistake I did, and reach for a burrowing marginal-marine crab or some other invertebrate as the tracemaker.

Geologists would be further fooled if fossil mole tunnels were intersected by genuine ghost-crab burrows, which would constitute a great example of a composite trace made by more than one species of animal. But why did the crabs burrow into the mole tunnels? Because it was easier. After all, the moles left hollow spaces and loosened sand over wide areas, practically begging ghost crabs to exploit these disturbed areas.

Anyway, I doubt many geologists would think of a small terrestrial mammal as a tracemaker for such burrows in sedimentary rocks formed in marginal-marine environments, although I’d love to be proved wrong on this. I’m hoping my writing about it here will help to prevent such confusion, and that whoever benefits from it will buy me an adult beverage as thanks.

In summary, this example of making a crab burrow out of a mole tunnel thus serves as a cautionary tale of how where we are when making observations in the field can influence our perceptions. But it also goes to show us how our wonderment with what we observe in natural environments can be renewed and encouraged by daring to be wrong once in a while, and learning from those mistakes.

Further Reading

Frey, R.W., and Pemberton, S.G. 1986. Vertebrate lebensspuren in intertidal and supratidal environments, Holocene barrier island, Georgia. Senckenbergiana Maritima, 18: 97-121.

Gorman, M.L., and Stone, R.D. 1990. The Natural History of Moles. University of Chicago Press, Chicago, Illinois: 138 p.

Harvey, M.J. 1976. Home range, movement, and diel activity of the eastern mole, Scalopus aquaticus. American Midland Naturalist, 95: 436-445.

Henderson, R.F. 1994. Moles. Prevention and Control of Wildlife Damage, Paper 49, University of Nebraska, Lincoln: D51-58. (Entire text here.)

Hickman, G.C. 1983. Influence of the semiaquatic habit in determining burrow structure of the star-nosed mole (Condylura cristata). Canadian Journal of Zoology, 61: 1688-1692.

Life Traces as Cover Art

Posted on April 30, 2012 by TMartin

I’ve been a long-time admirer of the artistic appeal of tracks, trails, burrows, nests, and other traces of animal behavior. My fondness for the beauty of traces also no doubt contributes to my science: after all, the longer I look at a trace, the more I learn about it. This sentiment accords with a long-time principle of paleontology, botany, and other facets of natural history, which is, “If you draw it, you know it,” with the added benefit of expressing your appreciation of natural objects to others through visual depictions.

Here it is: the cover for my upcoming book, Life Traces of the Georgia Coast: Revealing the Unseen Lives of Plants and Animals! The book is scheduled to be published by Indiana University Press in the fall of 2012, so be watching out for it then. But in the meantime, look at the beautiful cover art. Who created it, what inspired it, and what science lies behind its aesthetically pleasing composition? Please read on to find out.

My thinking about traces as objects of art is not very original, though, and in fact has been preceded by most of humanity. For example, animal tracks and other traces were common subjects of rock art extending back to the Pleistocene Epoch. Whether made as pictographs or petroglyphs, these traces of traces are in Australia, southern Africa, Australia, and Europe, with some tens of thousands of years old. Based on this tantalizing evidence, one could reasonably propose that the representation of animal traces through art composes an intrinsic part of our heritage as a species. Yes, I know, that’s a tough hypothesis to pursue any further. So I’ll leave it to my paleoanthropologist colleagues to work out (or not).

Petroglyphs that likely represent bird tracks, etched in Triassic sandstone by Native Americans hundreds of years ago (sorry, I’m a paleontologist, not an archaeologist). The pair of marks on the right is similar to the tracks made by a perching bird with three forward pointing toes and one rearward-pointing toe – such as an eagle – whereas those to the right may be like those of a roadrunner, which has an X-shaped foot. Petroglyphs are in northeastern Arizona, near Petrified Forest National Park.

Much more recently, trace fossils similarly inspired renowned ichnologist Dolf Seilacher, who also saw these vestiges of past behavior as lovely objects that fill us with wonder. As a result, in the mid-1990s, he conceived of a traveling exhibit and book showcasing tableaus of trace fossils and other sedimentary structures, titled Fossil Art. For this show – embraced by natural-history venues but mostly rejected by art museums – Seilacher prepared it by: (1) making latex molds of sedimentary rock surfaces; (2) pouring epoxy resin into the molds to make casts mimicking the original bedding planes; and (3) using indirect lighting to enhance details; and (4) assigning creative titles to each piece as if they were works of art.

So these artificial slabs are not human-made art in the traditional sense, but nonetheless invoke marvel, project splendor, and otherwise make us think, engaging the same senses and thought processes that accompany an appreciation of art. Moreover, the slim book Seilacher authored for the exhibit contains explanatory text about each of the objects, illuminated further by his marvelous illustrations and visual interpretations. I remember first seeing a version of this exhibit in Holzmaden, Germany in 1995, near Seilacher’s home in Tubingen, and most lately enjoyed strolling through it with other many ichnologists – and Seilacher himself – in Krakow, Poland in 2008.

World-renowned ichnologist and (oh yeah) Crafoord Prize winner, Dolf Seilacher, lecturing about the planning and execution of Fossil Art as an exhibit while it was showing at the Geological Museum of Jagiellonian University in Krakow, Poland in September 2008. Photograph by Anthony Martin.

A close-up of Wrong Sided Hands, one of the pieces displayed in Fossil Art, cast from a latex mold of a sample from Lower Triassic Buntsandstein of Germany. The piece is so-called because the false appearance of a “thumb” on the outside of the tracks originally led to the mistaken idea that the animal awkwardly crossed its own path with each step. This turned out to be wrong. Also, check out the mudcracks! Photograph by Anthony Martin.

Another close-up of a piece from Fossil Art, titled Shrimp Burrow Jungle (helpfully translated into Polish here). This one is based on burrow systems made by crustaceans during the Late Triassic in Italy, which became densely populated over time and hence contributed to overlapping systems. Photograph by Anthony Martin.

Hence during my writing of a book about the modern traces of the Georgia barrier islands, I was well aware of how some of these traces could likewise lend to artistic expression. Some of this mindfulness was applied to a collaborative artwork done with my wife, Ruth Schowalter, in which we took an illustration of mine from the book and used it as the inspiration for a large watercolor painting depicting traces that would form with rising sea level along the Georgia coast (discussed in detail here).

Nonetheless, it was especially important to think about traces as art when considering a potential cover for the book. Book authors know all too well that a well-designed, attractive cover is essential for grabbing the attention of a potential reader, so I had that practical consideration in mind. But I also wanted a cover that pleased me personally, sharing my love of beautiful traces with others, especially those varied and wondrous tracks, burrows, and trails I had seen and studied on the Georgia barrier islands during the past 15 years.

In such an endeavor, I also faced the added pressure of precedence set by my publisher, Indiana University Press. My book is part of a series by IU Press, called Life of the Past, which is widely admired not only for its comprehensive coverage of paleontological topics, but also for its fine cover art, showcasing works done by a veritable “who’s who” of “paleoartists,” So I knew the cover art for my book needed to both conform to this legacy of artistic excellence, but also stand out from other books in the series because of its unique themes. After all, this would be first book in Life of the Past focusing specifically on ichnology. Moreover, the book is more concerned on modern tracemakers and their environments, rather than plants and animals of pre-human worlds. This was done with the intention of demonstrating how our knowledge of modern traces helps us to better understand life from the geologic past, an intrinsic principle of geology called uniformitarianism.

Ideally, as an ichnological purist, I would have had a cover devoid of any animals, and just shown environments of the Georgia of the Georgia coast with their traces. Indeed, I did just that in some of my illustrations in the book, in which I purposefully omitted animals and left only their traces. This “ichno-centric” mindset actually serves a pedagogical purpose, in that it would echo the truism that many sedimentary rocks are devoid of body fossils, yet are teeming with trace fossils.

Figure 1.3 from Life Traces of the Georgia Coast, conveying a sense of the variety and abundance of traces on a typical Georgia barrier island, from maritime forest (left) to shallow intertidal (right). I purposefully drew this illustration using a more cartoonish technique to introduce broad search images of traces for people who may not ordinarily think about these. But also notice what’s missing from the figure: the animal tracemakers. Instead, only immobile plants are depicted. Would this make for good cover art? No and no, especially if you’ve seen the typical covers done for Indiana University Press books. Illustration by Anthony Martin.

Realistically, though, I also knew that modern traces, particularly those made in places as easy to visit as parts of the Georgia coast, would be more eye-catching if accompanied by some of their charismatic tracemakers in a beautiful, natural setting. After all, the Georgia coast has lengthy sandy beaches, dunes, maritime forests, and salt marshes, inhabited by a wide variety of animals, such as sea turtles, shorebirds, alligators, horseshoe crabs, ghost crabs, and many others.

I also knew that a paleoartist would not be as well suited to the task of creating a cover as someone who works more with modern environments. A better pick would be someone who was familiar with the landscapes, plants, and animals of the Georgia barrier islands, but also a fine artist. I briefly toyed with the idea of doing it myself, but already felt like far too much of the book had been “DIY,” and was not confident enough in my skills to put together a compelling cover in enough time before the book came together. An artfully done photograph was another possibility, so I sent several prospective examples to the editors for their appraisal, but these were all shot down for not having enough aesthetic elements for an attention-getting cover (i.e., traces + landscapes + sky + water = very difficult to get into a single photo).

Fortunately, through social connections that still happen despite the Internet and its incentives for becoming increasingly introverted, I met Alan Campbell through mutual friends in December 2008 at a dinner party on the Georgia coast. Fortuitously enough, our meeting was also just before Ruth and I did three weeks of field work on the barrier islands for the book. It was only fitting, then, that our first meeting was spent dining with both of us facing a Georgia salt marsh, filled with fiddler crab burrows and other such traces. Alan is a Georgia artist with much life experience along its coast, he has often portrayed its environments through gorgeous watercolors, and he has worked with scientists in the field.

Consequently, I kept Alan in mind as a potential cover artist for the next few years, and after I had finished the text and all figures for the book, I contacted him last year about my idea, while simultaneously suggesting him to the editors at IU Press. After much back-and-forth negotiations, with me in the middle, both parties finally came to an agreement, and Alan had a contract to do the artwork for the cover by December 2011.

To help Alan in researching his task, I sent him all of my illustrations and photos used in the book so that he would have an extensive library of trace images on hand for reference. He also had this blog as a source, in which I regularly write about Georgia-coast traces, explanations that are always accompanied by photographs and an occasional illustration. We also exchanged many e-mails and talked on the phone whenever needed. I told Alan my preferred cover would feature a coastal scene, but one filled with traces. He voiced a concern that the painting might become too “busy,” and the details might be lost in reduction of the image to the size

Alan’s contract specified that he would have preliminary study sketches would be done by February 1, and the final cover art was to be finished by March 30. He was only a little late with the study sketches (delayed by a minor operation), and I was delighted to see the following sketch in mid-February.

Study sketch by Alan Campbell for the cover of Life Traces of the Georgia Coast. Reprinted with his permission, and anyone else who want to use it, you have to ask him, too. By the way, every time you use original artwork without permission, a little kitten dies.

After a little bit of feedback from both me and graphic designers at IU Press, Alan went back to the drawing board (so to speak), and came up with the following watercolor painting.

Life Traces of the Georgia Coast, 2012, watercolor on paper, 14” X 18” by Alan Campbell. Again, if you want to use it, you have to ask him first and get permission. Remember those kittens? They’re alive now, but there’s no guarantee they’re going to stay that way.

I gave this artwork a big thumbs up, as did the people at IU Press. So once approved and the scan was sent to IU Press, it was up to the graphic designers there to pick out the typeface, color of the type for the main title, subtitle, author name, and placement of type without covering up the main composition of the painting. I had no say in this, and that’s a good thing, because they really knew what they were doing. It is a very nicely designed cover, and the only thing that would please me more is if they had produced a holographic image of it. (Maybe next year.)

The final cover art for Life Traces of the Georgia Coast revisited. Does it look a little different, now that you know more about how it came about?

I won’t spoil the fun for potential readers, scientists, and art appreciators by explaining in detail all of the ichnological, ecological, and geological elements incorporated into the cover. After all, I’d like to sell a few copies of the book, while also letting readers make their own personal discoveries. But hopefully all of you now have a better appreciation for how traces made by animals, our recognition and admiration for these, and artistic expression of them can all combine to contribute to a book that can be accurately judged by its cover.

Further Reading

Leigh, J., Kilgo, J., and Campbell, A. 2004. Ossabaw: Evocations of an Island. University of Georgia Press, Athens, Georgia.

Martin, A.J., in press. Life Traces of the Georgia Coast: Revealing the Unseen Lives of Plants and Animals. Indiana University Press, Bloomington, Indiana.

Morwood, M.J. 2002. Visions from the Past: The Archaeology of Australian Aboriginal Art. Allen & Unwin, Sydney, Australia.

Seilacher, A. 2008. Fossil Art: An Exhibition of the Geologisches Institut. Tubingen University, Tubingen, Germany.

Tomaselli, K.G. 2001. Rock art, the art of tracking, and cybertracking: Demystifying the “Bushmen” in the information age. Visual Anthropology, 14: 77-82.

Into the Dragon’s Lair: Alligator Burrows as Traces

Posted on March 15, 2012 by TMartin

American alligators (Alligator mississippiensis) tend to provoke strong feelings in people, but the one I encounter the most often is awe, followed closely by fear. Both emotions are certainly justifiable, considering how alligators are not only the largest reptiles living on the Georgia barrier islands, but also are the top predators in both freshwater and salt-water ecosystems in and around those islands. I’ve even encountered them often enough in maritime forests of the islands to regard them as imposing predators in those ecosystems, too.

Time for a relaxing stroll through the maritime forest to revel in its majestic live oaks, languid Spanish moss, and ever-so-green saw palmettos. Say, does that log over there look a little odd to you? (Photo by Anthony Martin, taken on St. Catherines Island.)

But what many people may not know about these Georgia alligators is that they burrow. I’m still a little murky on exactly how they burrow, but they do, and the tunnels of alligators, large and small, are woven throughout the interiors of many Georgia barrier islands. Earlier this week, I was on one of those islands – St. Catherines – having started a survey of alligator burrow locations, sizes, and ecological settings.

Entrance to an alligator burrow in a former freshwater marsh, now dry, yet the burrow is filled with water. How did water get into the burrow, and how does such traces help alligators to survive and thrive? Please read on. (Photograph by Anthony Martin and taken on St. Catherines Island, Georgia.)

In this project, I’m working cooperatively (as opposed to antagonistically) with a colleague of mine at Emory University, Michael Page, as well as Sheldon Skaggs and Robert (Kelly) Vance of Georgia Southern University. As loyal readers may recall, Sheldon and Kelly worked with me on a study of gopher tortoise burrows, also done on St. Catherines Island, in which we combined field descriptions of the burrows with imaging provided by ground-penetrating radar (also known by its acronym, GPR). Hence this project represents “Phase 2” in our study of large reptile burrows there, which we expect will result in at least two peer-reviewed papers and several presentations at professional meetings later this year.

Why is a paleontologist (that would be me) looking at alligator burrows? Well, I’m very interested in how these modern burrows might help us to recognize and properly interpret similar fossil burrows. Considering that alligators and tortoises have lineages that stretch back into the Mesozoic Era, it’s exciting to think that through observations we make of their descendants, we could be witnessing evolutionary echoes of those legacies today.

Indeed, for many people, alligators evoke thoughts of those most famous of Mesozoic denizens – dinosaurs – an allusion that is not so farfetched, and not just because alligators are huge, scaly, and carnivorous. Alligators are also crocodilians, and crocodilians and dinosaurs (including birds) are archosaurs, having shared a common ancestor early in the Mesozoic. However, alligators are an evolutionarily distinct group of crocodilians that likely split from other crocodilians in the Late Jurassic or Early Cretaceous Period, an interpretation based on both fossils and calculated rates of molecular change in their lineages.

Archosaur relatives, reunited on the Georgia coast: great egrets (Ardea alba), which are modern dinosaurs, nesting above American alligators (Alligator mississippiensis), which only remind us of dinosaurs, but shared a common ancestor with them in the Mesozoic Era. (Photograph by Anthony Martin, taken on St. Catherines Island, Georgia.)

Along these lines, I was a coauthor on a paper that documented the only known burrowing dinosaur – Oryctodromeus cubicularis – from mid-Cretaceous rocks in Montana. In this discovery, we had bones of an adult and two half-grown juveniles in a burrow-like structure that matched the size of the adult. I also interpreted similar structures in Cretaceous rocks of Victoria, Australia as the oldest known dinosaur burrows. Sadly, these structures contained no bones, which of course make their interpretation as trace fossils more contentious. Nonetheless, I otherwise pointed out why such burrows would have been likely for small dinosaurs, especially in Australia, which was near the South Pole during the Cretaceous. At least a few of these reasons I gave in the published paper about these structures were inspired by what was known about alligator burrows.

Natural sandstone cast of the burrow of the small ornithopod dinosaur, Oryctodromeus cubicularis, found in Late Cretaceous rocks of western Montana; scale = 15 cm (6 in). (Photograph by Anthony Martin, taken in Montana, USA.)

Enigmatic structure in Early Cretaceous rocks of Victoria, Australia, interpreted as a small dinosaur burrow. It was nearly identical in size (about 2 meters long) and form (gently dipping and spiraling tunnel) to the Montana dinosaur burrow. (Photograph by Anthony Martin, taken in Victoria, Australia.)

What are the purposes of modern alligator burrows? Here are four to think about:

• Dens for Raising Young Alligators – Many of these burrows, like the burrow interpreted for the dinosaur Oryctodromeus, serve as dens for raising young. In such instances, these burrows are occupied by big momma ‘gators, who use them for keeping their newly hatched (and potentially vulnerable) offspring safe from other predators.

Two days ago, Michael and I experienced this behavioral trait in a memorable way while we documented burrow locations. As we walked along the edge of an old canal cutting through the forest, baby alligators, alarmed by our presence, began emitting high-pitched grunts. This then provoked a large alligator – their presumed mother – to enter the water. Her reaction effectively discouraged us from approaching the babies; indeed, we promptly increased our distance from them. (Our mommas didn’t raise no dumb kids.) So although we were hampered in finding out the exact location of this mother’s den, it was likely very close to where we first heard the grunting babies. I have also seen mother alligators on St. Catherines Island usher their little ones through a submerged den entrance, quickly followed by the mother turning around in the burrow and standing guard at the front door.

Oh, what an adorable little baby alligator! What’s that? You say your mother is a little over-protective? Oh. I see. I think I’ll be leaving now… (Photograph by Anthony Martin, taken on St. Catherines Island.)

• Temperature Regulation – Sometimes large male alligators live by themselves in these burrows, like some sort of saurian bachelor pad. For male alligators on their own, these structures are important for maintaining equitable temperatures for these animals. Alligators, like other poikilothermic (“cold-blooded”) vertebrates, depend on their surrounding environments for controlling their body temperatures. Even south Georgia undergoes freezing conditions during the winter, and of course summers there can get brutally hot. Burrows neatly solve both problems, as these “indoor” environments, like caves, provide comfortable year-round living in a space that is neither too cold nor too hot, but just right. The burrowing ability of alligators thus makes them better adapted to colder climates than other crocodilians, such as the American crocodile (Crocodylus acutus), which does not make dwelling burrows and is restricted in the U.S. to the southern part of Florida.

• Protection against Fires – Burrows protect their occupants against a common environmental hazard in the southeastern U.S., fire. This is an advantage of alligator burrows that I did not appreciate until only a few days ago while in the field on St. Catherines. Yesterday, the island manager (and long-time resident) of St. Catherines, Royce Hayes, took us to a spot where last July a fire raged through a mixed maritime forest-freshwater wetland that also has numerous alligator burrows. The day after the fire ended, he saw two pairs of alligator tracks in the ash, meaning that these animals survived the fire by seeking shelter, and further reported that at least one of these trackways led from a burrow. The idea that these burrows can keep alligators safe from fires makes sense, similar to how gopher tortoises can live long lives in fire-dominated long-leaf pine ecosystems.

An area in the southern part of St. Catherines Island, scorched by a fire last July, that is also a freshwater wetland inhabited by alligators with burrows. The burrow entrances are all under water right now, which would work out fine for their alligator occupants if another fire went through there tomorrow. (Photograph by Anthony Martin, taken on St. Catherines Island.)

• Protection against Droughts – Burrows also probably help alligators keep their skins moist during droughts. Because these burrows often intersect the local water table, alligators might continue to use them as homes even when the accompany surface-water body has dried up. We saw several examples of such burrows during the past few days, some of which were occupied by alligators, even though their adjacent water bodies were nearly dry.

For example, yesterday Michael and I, while scouting a few low-lying areas for either occupied or abandoned dens, saw a small alligator – only about a meter (3.3 ft) long – in a dry ditch cutting through the middle of a pine forest. Curious about where alligator’s burrow might be, we approached it to see where it would go. It ran into a partially buried drainage pipe under a sandy road, a handy temporary refuge from potentially threatening bipeds. Seeing no other opening on that side of the road, we then checked the other side of the road, and were pleasantly surprised to find a burrow entrance with standing water in it. This small alligator had made the best of its perilously dry conditions by digging down to water below the ground surface.

Alligator burrow (right) on the edge of a former water body. Notice how water is pooling in the front of the burrow, showing how it intersects the local water table. The entrance also had fresh alligator tracks and tail dragmarks at this entrance, showing that it was still occupied despite the lack of water outside of it. (Photograph by Anthony Martin, taken on Cumberland Island, Georgia.)

Alligator burrows (left foreground and middle background) in a maritime forest, also not associated with a wetland but marking the former location of one. Although the one to the left was unoccupied when we looked at it, it had standing water just below its entrance. This meant an alligator could have hung out in this burrow for a while after the wetland dried up, and it may have just recently departed. Also, once these burrows are high and dry, bones strewn about in front of them also add a delicious sense of dread. Here, Michael Page points at a deer pelvis, minus the rest of the deer. (Photograph by Anthony Martin, taken on St. Catherines Island, Georgia.)

What is especially interesting about the American alligator is how the only other species of modern alligator, A. sinensis in China, is also a fabulous burrower, digging long tunnels there too, which they use for similar purposes. This behavioral trait in two closely related but now geographically distant species implies a shared evolutionary heritage, in which burrowing provided an adaptive advantage for their ancestors.

Thus like many research problems in science, we won’t really know much more about alligator burrows until we gather information about them, test some of the questions and other ideas that emerge from our study, and otherwise do more in-depth (pun intended) research. Nonetheless, our all-too-short trip to St. Catherines Island this week gave us a good start in our ambitions to apply a comprehensive approach to studying alligator burrows. Through a combination of ground-penetrating radar, geographic information systems, geology, and old-fashioned (but time-tested) field observations, we are confident that by the end of our study, we will have a better understanding of how burrows have helped alligators adapt to their environments since the Mesozoic.

Juvenile alligators just outside two over-sized burrows, made and used by previous generations of older and much larger alligators. How might such burrows get preserved in the fossil record? How might we know whether these burrows were reused by younger members of the same species? Or, would we even recognize these as fossil burrows in the first place? All good questions, and all hopefully answerable by studying modern alligator burrows on the Georgia barrier islands. (Photograph by Anthony Martin, taken on Sapelo Island, Georgia.)

Further Reading

Erickson, G.M., et al. 2012. Insights into the ecology and evolutionary success of crocodilians revealed through bite-force and tooth-pressure experimentation. PLoS One, 7(3): doi:10.1371/journal.pone.0031781.

Martin, A.J. 2009. Dinosaur burrows in the Otway Group (Albian) of Victoria, Australia and their relation to Cretaceous polar environments. Cretaceous Research, 30: 1223-1237.

Martin, A.J., Skaggs, S., Vance, R.K., and Greco, V. 2011. Ground-penetrating radar investigation of gopher-tortoise burrows: refining the characterization of modern vertebrate burrows and associated commensal traces. Geological Society of America Abstracts with Programs, 43(5): 381.

St. John, J.A., et al., 2012. Sequencing three crocodilian genomes to illuminate the evolution of archosaurs and amniotes. Genome Biology, 13: 415.

Varricchio, D.J., Martin, A. J., and Katsura, Y. 2007. First trace and body fossil evidence of a burrowing, denning dinosaur. Proceedings of the Royal Society of London B, 274: 1361-1368.

Waters, D.G. 2008. Crocodlians. In Jensen, J.B., Camp, C.D., Gibbons, W., and Elliott, M.J. (editors), Amphibians and Reptiles of Georgia. University of Georgia Press, Athens, Georgia: 271-274.

Acknowledgements: Much appreciation is extended to the St. Catherines Island Foundation, which supported our use of their facilities and vehicles on St. Catherines this week, and Royce Hayes, who enthusiastically shared his extensive knowledge of alligator burrows. I also would like to thank my present colleagues and future co-authors – Michael Page, Sheldon Skaggs, and Kelly Vance – for their valued contributions to this ongoing research: we make a great team. Lastly, I’m grateful to my wife Ruth Schowalter for her assistance both in the field and at home. She’s stared down many an alligator burrow with me on multiple islands of the Georgia coast, which says something about her spousal support for this ongoing research.

Life Traces of the Georgia Coast

Unseen lives of the Georgia barrier islands

Tag Archives: paleontology

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The Traces We Leave Behind: A Tribute to Jordi Maria de Gibert

Out of One’s Depth in the Ediacaran

Mistaken Point and the Limits of Actualism

Deep in the Dinosaur Tracks of Texas

Public Outreach via Ichnology: Traces for Kids

Public Outreach via Ichnology: The Prelude

Marine Moles and Mistakes in Science

Life Traces as Cover Art

Into the Dragon’s Lair: Alligator Burrows as Traces