Rewilding a Jurassic World

(Author’s note; The following post is a republished article of mine, originally published on June 12, 2014 by The Conversation and later republished by The New Republic, The Guardian, Quartz, and several other online news sources. However, this post is an embellished version, in which I include a paragraph on dinosaur microbiomes omitted from the original, and it uses my personal photographs and captions to illustrate its points about dinosaur paleoecology. So you might say this is the “director’s cut.” Many thanks to The Conversation editor Nick Lehr for helping turning my rough prose for the original article into one more readable for a general audience.)

Like many moviegoers this summer, I plan to watch Jurassic World. And because I’m a paleontologist, I’ll cheer for the movie’s protagonists (the dinosaurs) and jeer at the villains (the humans). But no matter how thrilling this movie may be, one question will plague me throughout: where are the dung beetles?

Jurassic-Morrison-Landscape-Walters-Kissinger-CarnegieThis mural depicts theropod dinosaurs (foreground) and sauropod dinosaurs (background) as part of a Late Jurassic ecosystem about 150 million years ago. OK, so this ecosystem has some producers (plants), primary consumers (herbivores, the sauropods), and secondary consumers (carnivores, the theropods). What’s missing from this picture that would be needed to make this a real, functioning ecosystem? If you said “Dung!” and “Dung beetles!,” you’re on the right track. (Mural by Robert F. Walters and Tess Kissinger (Walters & Kissinger) at the Carnegie Museum of Natural History, photograph by Anthony Martin.)

Dung beetles – which are beetles that eat and breed in dung – would be only one of many ecological necessities for an actual Jurassic World-style theme park. Yes, cloning long-extinct dinosaurs is impossible. But even if dinosaur genomes were available, the animals couldn’t simply be plopped anywhere.

So for the sake of argument, let’s say an extremely wealthy corporation did manage to create a diverse bunch of dinosaurs in a laboratory. The next step in building a Mesozoic version of Busch Gardens would be figuring out how to recreate – and maintain – the dinosaurs’ ecosystems. Accomplishing this goal would require a huge team of scientists, consisting (at minimum) of paleontologists, geologists, ecologists, botanists, zoologists, soil scientists, biochemists and microbiologists.

Such a team then would have to take into account countless interacting factors for the dinosaurs’ recreated habitats. And perhaps they could take a page from rewilding efforts that are currently taking place throughout the world.

In a memorable scene from the original Jurassic Park, paleobotanist Dr. Ellie Sattler examines an impressive heap of an ill Triceratops’s feces to look for digested remains of a toxic plant.

One of my favorite scenes in Jurassic Park (1993), when Dr. Ellie Sattler (played by Laura Dern) affirms her Ph.D. (= “Piled Higher and Deeper”) by unhesitatingly plunging her hands into a massive pile of Triceratops feces. Please note her sensible footwear, suitable for running away from theropods planning to add her to the local food web.

Here, the filmmakers touched on a key challenge for recreating an environment from a different geologic period. Many modern plants have evolved defenses against herbivores, which include toxins that can swiftly impair any animal that hasn’t adapted to them. Consequently, a time-traveling Triceratops would be taking a big risk with every visit to its local salad bar.

Paleobotanists could try to solve this problem by cataloging fossil plants that lived at the same time as plant-eating dinosaurs, before picking out descendants of those plants that are still around today. Still, plant lists will never be good enough to say whether or not a Triceratops, Stegosaurus, or Brachiosaurus ate those plants or if they could eat their descendants.

The same might hold true for carnivorous dinosaurs, which – for all we know – may have been picky eaters. For instance, although some Triceratops bones hold tooth traces of Tyrannosaurus, there’s no way to be sure a genetically engineered Tyrannosaurus would eat an equally inauthentic Triceratops (even if it were organic and free-range).

Triceratops-Tyrannosaur-Toothmarks-2 copyDid tyrannosaurs ever eat Triceratops? Oh yeah, and with gusto. Tooth trace fossils in Triceratops hip bones (red arrows) happen to match the dental records of Tyrannosaurus rex, which lived as the same time (Late Cretaceous, 65-70 million years ago) and place (western North America) as Triceratops. Also think about how much meat was covering that hip bone, which means the Triceratops must have been dead when this tyrannosaur was helping to recycle its body into the ecosystem. (Specimen in Museum of the Rockies and photograph by Anthony Martin.)

Yet another food-related dilemma is that we also are not quite sure how most dinosaurs digested what they ate. For instance, many modern animals – from termites to humans – require a suite of gut bacteria to break down and assimilate nutrients from food. Even if microbiologists somehow successfully recreated the microbiome of a dinosaur, how would you prevent it from acquiring modern gut parasites? Dinosaur coprolites (fossil feces) tell us that some dinosaurs had gut bacteria and parasites: but how to engineer the right bacteria and exclude the wrong parasites?

So despite a century of dinosaur flicks portraying tyrannosaurs and other predatory dinosaurs gratuitously munching humans, one bite of our species – or other sizable mammals – might make them sick. In other words, there’s no accounting for taste.

The lack of dung beetles in that same scene with Dr. Sattler also may have explained why the Triceratops’s feces were piled so high. We know from fossil burrows in dinosaur coprolites that dung beetles fed on dinosaur droppings at least 75 million years ago. Similarly, Late Jurassic dinosaur bones from nearly 150 million years ago hold the traces of carcass-eating insects.

Hadrosaur-Coprolite-Dung-Beetle-BurrowsA large, 75-million-year-old coprolite – attributed to the hadrosaur Maiasaura – filled with digested plant debris, but also with dung-beetle burrows. One burrow is sliced length-wise and runs diagonally (upper right to lower left), and another is in cross section and pointed toward you (upper right). Specimen is from the Museum of the Rockies but was part of a traveling display at Fernbank Museum of Natural History in the late 1990s. (Photograph by Anthony Martin.)

Termite-Borings-Dinosaur-Bone-DNMLate Jurassic (about 150 million-year-old) dinosaur bone with insect borings, which are credited to carcass- and bone-eating insects that used these bones for food or breeding soon after the dinosaur was dead. Specimen on display at Dinosaur National Monument near Vernal, Utah. (Photograph by Anthony Martin.)

This makes sense: wastes, bodies and other forms of stored matter and energy must be recycled in functioning modern ecosystems. Accordingly, to maintain the productivity of these dinosaurs’ ecosystems, animals that perform essential services to the ecosystem would need to be introduced. These include pollinators, such as bees, beetles and butterflies, as well as seed dispersers, like birds and small tree- and ground-dwelling mammals. Thus Masrani Global – the imaginary corporation tasked with creating Jurassic World – should have added entomologists (insect scientists), ornithologists and mammalogists to the career opportunities page on its mock website.

Can we learn anything useful from such fanciful reconstructing of long-gone ecosystems, where large animals once roamed? Sure. In so-called “rewilding” projects, imagination meets real science. These projects, which attempt to restore ecosystems by closely mimicking their previous iterations, often include reintroducing locally extinct animals.

Perhaps the most famous and successful of such rewilding projects began just after the release of the original Jurassic Park. In 1995, wolves were reintroduced to Yellowstone National Park. Although admittedly not as exciting as releasing a pack of velociraptors into the woods, the reintroduction of wolves – which had been extirpated from the area earlier in the 20th century – had a dramatic restorative effect.

Wolf-Tracks-Lamar-YellowstoneIf you looked for these tracks in Yellowstone National Park before the original Jurassic Park came out in 1993, you would have been disappointed. They’re from gray wolves (Canis lupus) and are signs of a now-thriving population of these apex predators reintroduced to the Greater Yellowstone Ecosystem in 1995, which has since caused big changes there. (Photograph by Anthony Martin.)

After the wolves gorged on elk – which, without predators, had overpopulated the region – riverine foliage grew more lushly. This prevented erosion and expanded floodplains, which gave beavers a better habitat to get to work damming rivers. A similar experiment is taking place in Europe, where increased numbers of large carnivores, such as wolves, bears and lynxes, are reshaping their ecosystems closer to their original states.

Bolstered by these successes, rewilding proponents have even proposed reintroducing elephants, lions, cheetahs and other animals to parts of North America as ecological proxies to mammoths, American lions and American “cheetahs” that lived only a little more than 10,000 years ago in those areas. Given the much shorter elapsed time since their extinction, enough similar species today and no need for genetic engineering, a “Pleistocene Park” – Pleistocene being the geological epoch that was about 2.5 million to 11,700 years ago – would be far easier to achieve than a Jurassic World (while also being more alliterative).

Pleistocene-Park-YellowstoneYou want a “Pleistocene Park”? Here’s a start, with herds of large primary consumers (Bison bison, otherwise known as “bison”) and grasslands in Yellowstone National Park, which overlap in range with secondary consumers wolves and grizzly bears. Now just add some elephants, lions, cheetahs, and a bunch more dung beetles, and you should be set. Wait a minute: you say the National Park Service wouldn’t approve of that? Oh well, one step at a time. (Photograph by Anthony Martin.)

So to any corporations out there that are thinking of making such a park, do us a big favor: whatever you do, don’t forget to include dung beetles.

Flight of the Quahogs

Let’s try a science-education experiment. Give a child a live clam and ask, “Can this animal fly?” and I predict her or his answer – accompanied by much giggling – will be “No!’ But if you ask, “Can you fly?”, the answer may change, especially if this child has already flown on an aircraft. So of course humans can fly, but to do this, they require machines, paragliders, or other technological aids in order to move through the air and – this is important – arrive on the ground safely.

Shattered-Quahogs-Pier-Jekyll-IslandFor clams that try to fly, they end up with more than shattered dreams. How did these clams (Mercenaria mercenaria, also known as quahogs or “hard clams”) end up doing Humpty-Dumpty impressions on a wooden pier? Please read on. (Photograph by Anthony Martin, taken on Jekyll Island, Georgia.)

In a similar way, clams can fly. They just need a little help from other animals that can fly and willingly give them a temporary lift from the earth they and their molluscan relatives have known for all of their evolutionary history. Compared to most of our forays into the air, though, these flights are much more limited. Clam aerial exploits are brief and mostly vertical, with little time for them to appreciate the view from above or otherwise experience unusual sensations. They go up, then they come down, and fast.

Clams do not have landing gear. So they can hit the ground hard, especially if their free fall happened after a lengthy trip up into the air and the ground surface is hard: think of a sandflat at low tide, a paved parking lot, or a wooden boardwalk. A a result, the most common end to clam flights is a shattered shell, which is quickly followed by the demise of the clam as it is consumed by the very same animal that bestowed it with flight, however brief and self-serving.

Impact-Trace-Seagull-Clam-DropTraces of a unidirectional vertically oriented clam flight (otherwise known as “falling”) that did not end well for the clam, but worked perfectly for the flying animal that took it for a ride. Notice the impact trace on the hard sandflat, outlining the ribbed shell of the clam (probably Dinocardium robustum) and bits of shell. Most of the probably-still-alive-but-definitely-dying animal  was dragged off to a nearby spot so that its soft parts could be eaten by the same perpetrator that took it for a ride. (Photograph by Anthony Martin, taken on Sapelo Island, Georgia.)

So just what flying animals do such dastardly deeds, taking hapless clams up for a ride, only to drop them to a certain death? By now the gentle reader has probably figured out birds are responsible for this blatant bivalvicide, and some may have already known that seagulls are the most likely culprits. In some coastal areas and during low tides, some seagulls fly over exposed sandflats and mudflats, searching for the outlines of clams buried below the surface. These avian ichnologists then swoop down, land, pick up the clam with their beaks, take off, and then once high enough, they drop them, serving up instant raw clam on the half (or quarter, or eighth) shell. Typically all that is left is a jigsaw puzzle of clamshell pieces and the seagull perpetrator’s footprints, but with the latter only evident on muddy or sandy surfaces amenable to preserving tracks.

Seagull-Tracks-Eaten-ClamIchnological evidence of who killed the clam, provided by the tracks a laughing gull (Larus altricilla).The other half of the shell was broken by its falling onto the sandflat elsewhere, then the gull carried its clam on the half-shell to a more scenic place for its meal. (Photo by Anthony Martin, taken on Little St. Simons Island, Georgia.)

I found this behavior so compelling that I started my book Life Traces of the Georgia Coast (2013) with a story about a laughing gull (Larus altricilla) and the traces of its unwitnessed predation on an Atlantic cockle (Dinocardium robustum), seagull behavior on the Georgia coast. I was not the first person to note this method of clam-smashing by seagulls, as it has been documented by other scientists in parts of the U.S. and abroad, and has been caught on video. Amazingly, though, despite more than 15 years of visiting the Georgia coast, I had never actually witnessed seagulls dropping clams. instead I had only performed post-mortem forensics, in which I would find broken clamshells on hard sandflats accompanied by seagull tracks, telling tales of murder most fowl.

Video footage of a western gull (Larus occidentalis) picking up a clam, flying up about 10 meters (> 30 feet), and dropping it onto rocks to crack it open. After this doesn’t work the first time – and after shooing away a potential clam-stealing rival – it tries again, and is presumably successful. It’s almost as if this gull is using a scientific methodology, isn’t it? (The videographer is only credited as ‘Trisera’ on the YouTube page, and I don’t know where it was filmed, but suppose it’s on the western coast of the U.S.)

Seagull-Cockle-Predation-DiagramHere’s the first illustration a reader will see in my book, Life Traces of the Georgia Coast (2013, Indiana University Press), which I drew to provide a visual forensic analysis of how an Atlantic cockle met its demise at the hands of – er, I mean, wings and bill of – a laughing gull. Part (a) depicts the gull landing after recognizing the outline of the cockle from the air, stopping, and extracting it from the sandflat. Part (b) shows where the cockle was dropped and broken successfully, accompanied by the gull landing and trampling the area as it enjoyed its clam dinner.

This meant I was more than overdue to get visual confirmation of gulls killing clams, which was finally granted just a few weeks ago during a recent trip to Jekyll Island (Georgia). It was the day after I had given an invited talk at the annual meeting of The Initiative to Protect Jekyll Island environmental group, and while my wife Ruth and I were relaxing before leaving the island, but of course were also observing whatever nature we could.

In that spirit, and while sitting on a deck on the west side of the island and looking at a mudflat (in between swatting sand gnats), we noticed a seagull flying about 10 meters (>30 feet) above a wooden pier. At one point, it paused its ascent, and we saw an object fall from its mouth and down toward the pier. Thunk! We clearly heard the impact of the object correlate with what we saw, and with much excitement realized that we had just witnessed seagull clam-cracking for the first time.

Jekyll-Island-Mudflat-Dead-Clams A mudflat replete with mud snails (probably Ilyanassa obseleta), grazing away and making gorgeous meandering trails on the western side of Jekyll Island (Georgia). But wait, what are those big white chunks on the same surface?

Dead-Clams-Mudflat-Jekyll-IslandWhy, look at that: hard clams (Mercenaria mercenaria) in an unnatural state, i.e., disarticulated, broken, and dead on the surface of the mudflat. These clams normally burrow into and live under the mud, and usually manage to stay intact if they stay below the surface. The pieces of clams here must have bounced off the wooden pier, which is casting a shadow in the lower right-hand side of the picture. (Both preceding photographs by Anthony Martin and taken on Jekyll Island, Georgia.)

What was most surprising to me about this broken-shell assemblage on the pier was how it was represented only by the hard clam, or quahog (Mercenaria mercenaria). These thick-shelled clams are quite common in sparsely vegetated muddy areas of salt marshes, burrowing into the mud and connecting their siphons to the surface so that they can filter out suspended goodies in the water during high tides. During low tides, however, they become vulnerable to avian predation. Despite being “hidden” in the mud, somehow the seagulls spotted them from the air, landed next to them on the mudflat, and pulled them out of the mud. They then used the nearby pier as an anvil, and the clam’s hard, thick shell unwittingly became its own hammer when they hit the pier after falling from a fatal height.

Shattered-Quahogs-Jekyll-Pier-MartinThe horror, the horror: a clam killing “ground,” thoughtfully supplied by humans for seagulls in the form of a long, hard, wooden pier. (Photograph by Ruth Schowalter and Yours Truly for scale, taken on Jekyll Island, Georgia.)

OK, now it’s time to think about broken clams and deep time. If you found such an assemblage of broken shells of the same species of thick-shelled clams in a geologic deposit, how would you interpret it? Would you think of these broken shells as predation traces, let alone ones made by birds? Which also prompts the question, when did seagulls or other shorebirds start using flight and hard surfaces to open clams? Did it evolve before humans, and if so, was it passed on as a learned behavior over generations as a sort of “seagull culture”?

All of these are good questions paleontologists should ask whenever they look at a concentration of broken fossil bivalves that are all of the same species, and overlapping with the known geologic range of shorebirds. In short, these may not be “just shells,” but evidence of birds using gravity-assisted killing as part of their predation portfolio.

Tales of Trails by Seahorse Tails

I’ve always been a big fan of aquariums. Having grown up in the landlocked Midwest and not seeing an ocean with its bountiful life until I was 20 years old, I am still drawn to the old-school charm of big tanks filled with salt water and populated by exotic fish and other sea critters. These environments, however artificial, never fail to inspire awe and wonder. Even better, they often teach me something new and relevant each time I pay closer attention to what they hold.

Seahorse-Making-Resting-TraceA seahorse, of course, is not a horse. But that’s not the only way seahorses differ from horses, in that they leave trails instead of tracks. Intrigued? Yeah, me too. (Photograph by Anthony Martin, taken at the UGA Aquarium, Skidaway Island, Georgia.)

Nonetheless, I also have a “problem,” which manifests itself whenever I’m at an aquarium, walking along a beach, sitting on a park bench, driving down a  road, or, well, conscious. As an ichnologist, I’m constantly looking for animal traces. Then once found, I study these traces carefully so that they may inform me whenever I see similar traces in the fossil record. But because I’m a land-dweller and rarely have the opportunity to snorkel or scuba-dive, aquariums come in handy for observing traces of aquatic animals I might not often see. Particularly helpful are aquariums in which the people caring for them were kind enough to include sand on their bottoms (the aquariums, that is).

So last weekend, while leading a class field trip to the Georgia coast and after a wonderful boat ride to Wassaw Island and back, I eagerly joined my students in viewing a salt-water aquarium. This particular venue was the UGA Aquarium (UGA = University of Georgia, Athens) is maintained by the UGA Marine Extension Service (MAREX) on Skidaway Island, Georgia. Our visit was especially satisfying because we were there on a Sunday afternoon, when the aquarium is closed to the public. This luxury afforded us plenty of room and quietude, qualities that are rumored to enhance learning.

Within just a few minutes of entering the main room, one tank to the right caught my eye, and not just because of its pretty colors, but for its denizens and traces on the sandy bottom of that tank. It contained seahorses, fishes that are so odd compared to other fishes, we humans had to compare them to hoofed domesticated mammals. The best part of all, though, was that this tank had lots of intersecting grooves and circular imprints on its sandy surface, which no doubt had been made by the seahorses.

Seahorse-Making-TrailA seahorse (Hippocampus sp.) showing off its lack of swimming skills by moving along the sandy bottom of a tank. Gee, what are all of those meandering and intersecting grooves in the sand and circular imprints? I wonder what made those? Sorry, first guess doesn’t count. (Photograph by Anthony Martin, taken at the UGA Aquarium, Skidaway Island, Georgia.)

All seahorses are under the genus Hippocampus, which consists of more than fifty species. Evolutionarily speaking, they are ray-finned fish (actinopterygians) and share a common ancestor with pipefish and sea dragons (Sygnathidae). The oldest known fossil seahorses are in Miocene Epoch rocks, from about 13 million years ago. Besides their equine-like profiles, they are well known for their prehensile tails, which can either grasp onto algae, sponges, or corals, or curl up underneath them as they swim.

However, seahorses are never going to inspire bets at underwater race tracks, as they are among the slowest-swimming of fish, propelled mostly by tiny pectoral fins while moving upright. Still, they don’t need to be fast, as they are very successful predators, with about 90% accuracy in nabbing fast-swimming small crustaceans that get too close to their mouths. Seahorses also don’t need to swim away from larger predatory fishes that might wish to pick them from a seafood menu. Whenever seahorses attach to algae and corals, they sway in harmony with their temporary hosts, effectively blending in with their surroundings.

One point I keep in mind whenever visiting an aquarium, zoo, or other such enclosures is how these can alter so-called “normal” behaviors of their animals. In this instance, the smaller space of this tank, combined with little material for attachment, meant these seahorses were more likely to swim along its bottom then they might in an open ocean. Accordingly, they had made lots of traces in the sand: mostly undulating grooves, but a few circular impressions from their curled tails plopping onto one side or the other.

Seahorse-Making-Trail-2A seahorse making tail trails while swimming along the bottom of an aquarium. Notice how the trail would become less linear, wider, and more circular if the tail flops over to one side or another, involving a greater area of the curled end. (Photograph by Anthony Martin, taken at the UGA Aquarium, Skidaway Island, Georgia.)

Seahorse-TrailsA close-up of those trails left by swimming seahorses dragging their tails along a sandy surface. Also, check out the overlapping circular “plop” traces on the right, made by the curled part of the tail? (Photograph by Anthony Martin, taken at the UGA Aquarium, Skidaway Island, Georgia.)

What’s the take-home message of these observations for ichnologists, geologists, and paleontologists? That experience matters, as does questioning preconceived notions about what we might observe from the geologic record. Take a look at the preceding photo, and tell me – quite honestly – that your very first interpretation of the tracemakers would have been “fish,” let alone “seahorse.” Instead, I think nearly everyone (yes, me too) would have reached for the easiest answer, which would have been “worm trails,” similar to how geologists reflexively apply “worm burrows to anything small, tubular trace fossil they encounter at an outcrop. Wrong, wrong, wrong.

So next time when looking at rocks formed in marine environments – whether from the last 13 million years or much older – and these rocks host lots of “worm trails” on their surfaces, ask yourself who else could have made such trails, and how. Reach beyond easy and ordinary explanations, and imagine. Oh, and when you go to aquariums, don’t just look at their sea-life, but also the traces of the sea-life in them.

Acorns, Mighty Oaks, and Raccoons

Despite more than 15 years of visiting the Georgia coast, studying its traces, and taking students on field trips to its barrier islands, I always marvel at how each trip is different, bestowing new insights and lessons to both me and my students. So a trip there this past weekend was no exception, and perhaps the most intriguing phenomenon I encountered during it was of some “mere” scrapings in a sandy road on Wassaw Island, Georgia.

Raccoon-Scrapings-Acorns-WassawWho needs a Mystery Date when you can have a Mystery Trace? Here we have some enigmatic scrapings in a sandy road on Wassaw Island, Georgia. What could have made these, and why? (Photograph by Anthony Martin; scale in centimeters.)

Wassaw Island is a National Wildlife Refuge, and I’ve mentioned it before as the one island of the Georgia coast that most closely approaches the ideal of “pristine,” a label blithely applied to nearly any Georgia barrier island regardless of how much humans had modified their landscapes. Current estimates are that it Wassaw only about 600 years old, which means that Native Americans had barely populated it by the time the Spanish arrived in the 16th century. Thus whenever I teach my biannual Barrier Islands class, I like to include a field trip to Wassaw Island so my students can appreciate the close-to-natural state of its ecosystems. We then contrast their experiences there by visiting overdeveloped Tybee Island on the same weekend, giving my students the opportunity to think about “before and after” conditions of Georgia barrier-island ecosystems.

Even better for my students, our leader for the field trip to Wassaw was not me, but John “(“Crawfish”) Crawford, one of the most knowledgeable naturalists on the Georgia coast. Employed by the University of Georgia Marine Extension Service on Skidaway Island, John regularly takes groups on an open boat to Wassaw Island for day trips. These trips never disappoint for the sheer variety and richness of natural history learned along the way, whether on the boat trip there and back, or on the island itself. I’ve been to Wassaw four times with John as a guide, and each time with him have seen something novel there. (I mean, how often do you see a decapitated seagull?)

Wassaw-Interior-HikingInto the Woods, Wassaw Island style! With our intrepid guide (John “Crawfish” Crawford) leading the way into the maritime forest of Wassaw, my students were in for a world of discovery on this beautiful Georgia barrier island. (Photograph by Anthony Martin.)

Just one example from this most recent trip I’d like to share are traces I have never before seen, or, more likely, never before noticed. We encountered it while walking down a sandy road on Wassaw used more often by deer and alligators than humans. The traces were systematic and widespread scrapings of the top few centimeters of the road, some of which resolved themselves as curved to linear features with finer grooves in their interiors. Because they did not match the feeding traces of feral hogs (Sus scrofa) or nine-banded armadillos (Dasypus novemcinctus), I was intrigued. Who made these, and why?

Raccoon-Scrapings-Acorns-WassawJust in case you missed it the first time, here’s that photo again. Yes, this will be on the exam: why do you even ask?

A closer look revealed the traces were overlapping sets pf five evenly spaced grooves, corresponding with five thin-fingered hands. These could only belong to the most dextrous, industrious, and resourceful denizens of maritime forests and other environments on the Georgia coast, raccoons (Procyon lotor). When I queried John about these traces, he confirmed that not only were they made by raccoons, but also were a result of their “mining” the sand. The raccoons, using their front paws, methodically raked the loose sand to expose shallowly buried acorns dropped by the many old and mighty oaks lining the road, indulging in an all-you-can-eat acorn feast.

DSCN4416Close-up of the same mystery trace seen in the previous photo, but this time more groovy. Check out the curving, parallel set of five grooves (left) and the partial track (right), telling us that a masked bandit left its mark. (Photograph by Anthony Martin; scale in centimeters.)

Although raccoons are infamously omnivorous, in winter months they depend on acorns for much of their diet. Thus considering that the Georgia coast was still in winter, and that a sub-freezing cold front had just passed through the area a few days before, it was not surprising to see this evidence of extensive acorn foraging.

OK, time to replace my floppy coastal-geologist hat with my more stylish paleontologist hat to ask this question: Would such traces preserve in the geologic record, and if so, would they be recognizable for both the tracemaker (raccoon) and behavior (foraging)? Probably not for both, as the loose quartz-rich sand in a maritime forest would have few chances of being buried intact and cemented in a way that would “freeze” the details needed to discern both tracemaker and its intent. Yet these traces would lend some insights to interpreting disturbed zones in the upper parts of fossil soils, especially those that might have preserved acorns or other nuts in them.

So next time you’re in a maritime forest during the winter and come across some odd scrapings in the road, take a closer look and ask yourself a few questions about them. Who made them? Why did they make them? How do these traces relate to the broader ecology of the area? Would they be preserved in the fossil record, and if so, could we properly interpret them? Then ask yourself what you’ll find next time you go to the same place and look just a little bit closer.

Jots and Tittles of Beaks and Feet

The wide variety of modern bird behaviors – as well as the traces that result from these behaviors – continue to captivate and fascinate me. Given recent revelations of birds’ dinosaurian ancestry and the interrelationships of modern birds (an evolutionary history spanning more than 150 million years), this wonderment should be expected. Accordingly, then, the traces made by modern birds can be equally varied, and can serve as guides to the behaviors of their predecessors, especially when made by birds interacting with ecological margins (ecotones).

Grackle-Crow-Tracks-TybeeA mixture of tracks left by boat-tailed grackles (Quiscalus major) and American crows (Corvus brachyrhynchos) on wind ripples in the upper part of a sandy beach. So if paleontologists found something similar in the geologic record, would they be able to say more than “Looks like a bunch of birds were walking around”? That’s why we look at modern traces and their associated behaviors: to get beyond such easy (and terribly incomplete) answers. (Photograph by Anthony Martin, taken on Tybee Island; pen is about 15 cm (6 in) long.)

The most recent example I witnessed of bird tracemakers and their traces in an ecotone setting was last month on Tybee Island (Georgia). Tybee is a barrier island just east of Savannah, and one I had visited in May, when I noted burrowing wasps in the coastal dunes there. The tracemakers were boat-tailed grackles (Quiscalus major), a passerine bird (“songbird”) that people commonly see and hear along the Georgia coast. Grackles belong to to an evolutionarily related group (clade) called Icteridae, colloquially known as “blackbirds.” I frequently see grackle tracks on the upper parts of beaches and in the dunes, where they are oftentimes the most common vertebrate traces above the high tide mark on Georgia shorelines.

What was strikingly atypical this time, though, was how all of the grackles I saw making tracks were adult females. Female grackles are distinguished from males by their brown coloration, whereas the males are iridescent black, almost deep purple when viewed in the right light. Female adult grackles are also noticeably smaller than adult males, at about 70% their lengths and half their weights. Like most passerine birds, grackles have four-toed anisodactyl feet, with the “thumb” (digit I) pointing directly backwards with respect to its three forward-pointing toes (digits II-IV). Such tracks show their feet are well adapted for grasping branches in trees; yet they hang out along shorelines and nest near water bodies. I also wondered whether the tracks of this gender-sorted assemblage could be distinguished from those of the larger males, but didn’t get a chance to test this idea.

Boat-tailed-grackles-foraging-TybeeGirlfriends going out for a bite to eat by the beach: a group of boat-tailed grackles – all female adults – foraging in between the sea oats on the south end of Tybee Island. Here they were on the seaward side of the dunes, and just before sundown. (Photograph by Anthony Martin.)

Yet it wasn’t track sizes that caught my attention: it was what they were doing and the traces they were leaving. They were actively foraging, walking in between stalks of the sparsely populated sea oats (Uniola paniculata), which were barely holding down the dunes. This meant lots of slow, methodical walking with their heads down, and beaks actively snatching anything of interest. What were they finding and eating? On an over-developed island like Tybee, it could be almost anything. Grackles are notoriously omnivorous, which explains why they’ve easily adapted and thrived along the eastern coast of the U.S. despite extensive human alterations to this island and elsewhere.

Boat-tailed-grackles-foraging-Tybee-2Grackles in different feeding postures: two with their heads down and feet together (foreground and right), and another with her head up and left leg ahead of her right, and all after walking slowly and stopping often. With that in mind, think of the trackway patterns that would correspond with these movements and postures. (Photograph by Anthony Martin, taken on Tybee Island.)

So here’s what’s cool: these grackles were eating locally by chowing down on sea oats. That’s right, given all of the human-provided junk food they had available, they were going for the all-natural, organic, raw, and totally vegetarian option. (Tragically, it was not gluten free. But I think they were OK with that.) As a result, their tracks showed lots of short steps (diagonal walking) punctuated by “T-stops,” where they stopped to place their feet side-by side (making a “T” pattern), all of which were accented by beak traces, the last of these intersecting depressions formerly occupied by the sea-oat grains.

Boat-tailed-grackle-eating-sea-oats-TybeeA close-up of the grackle from the previous photo, showing exactly why it stopped it with its feet together and put its beak down to the sand: fallen grains of sea oats. (Photograph by Anthony Martin, taken on Tybee Island.)

Boat-tailed-grackle-sea-oat-in-beak-closeup-trace-TybeeAnother close-up of a grackle, but with sea oats in her beak. More importantly, check out the tracks behind her, the little depression where the oats laid on the sand (arrow), and the beak mark next to it that she made just before grabbing the grains. (Photograph by Anthony Martin, taken on Tybee Island.)

Grackle-Foraging-Tracks-Tybee-2

Boat-tailed grackle tracks that say, “I’m out looking for food, and whole grains only, please.” Note the “T-stop” pattern in the tracks and a beak impression within the trackway (center bottom) coinciding with some sea-oat grains, and a similar set of traces toward further down the trackway. (Photograph by Anthony Martin, taken on Tybee Island.)

So if you’ve read anything written by me before now, you probably know what I’m going to do next. (No, not that. But maybe next time.) I’m probably going to say, “Hey y’all, why don’t you look for traces like these next time you’re out walking along the beach?” But I’m also likely to say, “Gee, I wonder if traces like these would show up in the fossil record?” Both are important questions to keep in mind, even though the first deals with the here and now, whereas the other dives into deep time.

As a paleontologist, though, I’m all about the deep-time question. For example, when did the ancestors of grackles and other blackbirds start eating seeds from the ancestors of the sea oats, and in coastal environments? How would we know when these proto-grackles started having cereal for breakfast? If any trace fossils that look like the ones shown here do somehow got preserved, they should help connect those dots between all of the genes, bones, and other scientific evidence we use to figure out the evolution of this diverse clade of blackbirds.

Berlin-Specimen-ArchaeopteryxYeah, I know, it’s a body fossil. But hey, it’s the Berlin specimen of Archaeopteryx, probably the most famous body fossil in the world, so it’s OK. I was lucky enough to see it in person at the Museum für Naturkunde in Berlin early last month, and like most paleontologists who see it, I was awestruck by its 150-million-year-old beauty. Understandably, then, the evolutionary history of birds was on my mind when – three weeks later – I watched those grackles making traces on a Georgia beach. Will Archaeopteryx trace fossils ever be found? Let’s hope so, and if they do, they deserve to be as famous as this specimen. (Photograph by Anthony Martin.)

Jurassic World’s Trailer Traces

One of the most momentous events of the post-Jurassic world happened last week with the online release of the official trailer for the upcoming movie Jurassic World. Yet within mere hours of its release, a great wailing and gnashing of teeth arose from dinosaur nerdom, as professional paleontologists and fervent paleo-fangirls and paleo-fanboys alike jumped onto it like a ravenous pack of naked, oversized, bunny-handed velociraptors (or deinonychosaurs: whatever).

Jurassic-World-ToothOwen (Chris Pratt): “Looks like a large theropod dinosaur tooth.” Claire (Bryce Dallas Howard): “That’s not going to tell us anything. Why don’t you look at its toothmarks right next to you?” That’s just one small sample of how I would rewrite the Jurassic World script from an ichnological perspective, neatly repairing its reputation as a scientifically accurate film while retaining blockbuster entertainment value. (This still image and all others in this post were stolen shamelessly from the Jurassic World trailer.)

You see, this trailer – which lasted for all of 161 seconds – contained 257 scientific inaccuracies, which comes out to about 1.6 errors/second. OK, maybe I just made up that number, much like how some people make up movie plots, scripts, and characters. Nonetheless, the trailer had scenes depicting featherless theropods, elephant-skinned sauropods, and a non-dinosaur mosasaur that was far too big, had a frill on its back, and a non-forked tongue. It’s almost as if these were genetically recreated monsters, and not the original animals from the Mesozoic Era. Oh, the waste! Oh, the humanity!

Anyway, let’s talk about something that really matters, like traces. As far as I know – and like many others on the Internet, I plan to stay ignorant of anything that might add to my present knowledge – not one of those paleo-critics, or even the critics of the paleo-critics, mentioned the totally awesome and epic traces shown in this trailer. This egregious oversight once again reinforces my oft-asserted point that ichnology is the Rodney Dangerfield of paleontology.

So that’s why I’m here, to enlighten the masses and convert y’all to the Church of Ichnology, where there’s no tithing, dancing and drinking are required, and you can leave the church any time you feel like it. I’ve also covered this beat before, having reviewed the ichnology of Jurassic Park, which was an entire movie, not just a trailer. Even better, I know a little bit about dinosaur ichnology, having just written a book on that topic (Dinosaurs Without Bones, if you must know).

What traces in are in the trailer, you ask? The first ones shown are at 1:39, revealed with a shot panning up a concrete wall. There on the wall are sets of three more-or-less parallel scratches, some straight and some curved. The scratches vary in lengths, and a few cross-cut each another. In one set the scratches are not parallel, but form more of a fan pattern.

Jurassic-World-Wall-Scratches-1I knew it was worth sitting through the first 1:30 of this trailer – check out those scratch patterns!

Of course, the preceding picture means little to an ichnologist unless it has a scale. I mean, were these from Compsognathus, or something a lot bigger? Fortunately, at 1:47, Chris Pratt provides a means of comparison by placing his hand on one of the scratches, and it looks like his three middle fingers approximate the width of that mark.

So let’s assume his hand proportions are about 1.4 times the size of mine, a supposition that can only be tested by the two of us having a beer together. (Hey, it could happen.) Accordingly, we will name this conversion factor the Chris Pratt Manual Ratio™ (CPMR). My three middle fingers bunched together are 5 cm (2 in) wide, which, after multiplying it by the CPMR, would make this scraping about 7 cm (2.75 in) wide. The spaces between the scratches seem to be about twice as wide, or 15 cm (5.5 in). This would make the entire set – three scratches and the two spaces between them – 51 cm (20 in) wide. These are twice as wide as some of the biggest known theropod dinosaur tracks. Or, as I like to say whenever I encounter grizzly-bear scratches on trees: “That ain’t no squirrel.”

Jurassic-World-Wall-Scratches-3Put your hands on the traces, and feel their healing power and redemption! Repeat the Holy Trinity of the Church of Ichnology with me: Substrate, Anatomy, and Behavior! Amen, brothers and sisters!

Based on my detailed study of these traces for at least two minutes (perhaps less), as well as Chris Pratt’s concerned gaze following these scracthes up the wall, I am interpreting them as traces made by three claws on the feet and hands of its tracemaker, with the wider sets coming from feet and the narrower ones from hands. Overall, these traces would be anatomically appropriate for theropod dinosaurs, many of which had three digits on its feet and hands with sharp claws. Moreover, this would have been a theropod dinosaur with impressively endowed forelimbs, sufficient for helping to pull it up a wall (sorry, T. rex).

Big-Three-Toed-Foot-With-Claws-Jurassic-WorldWhy, that looks like an enormous three-toed foot with robust claws on their ends, and in motion as it chases the presumed protagonist of Jurassic World. Who could’ve predicted that, based on mere ichnologically based foreshadowing?

The behavior of the tracemaker can also be interpreted by looking for where the “feet” traces cross-cut the “hand” traces on the wall. This pattern would have been made by an upward movement of the tracemaker as it climbed the vertical surface. In short, these are escape traces, and they were made by a very large theropod-like dinosaur. To his credit, Chris Pratt’s character (“Owen”) totally got this.

Jurassic-World-BonesChris Pratt isn’t just a Guardian of the Galaxy and a dinosaur handler: he’s also an ichnologist. (By the way: what’s with the bones behind him that don’t have any toothmarks on them? And why aren’t my paleontologist friends outraged about that unforgivable error?)

Any other traces in the trailer? Oh yeah, and it’s a good one. At 1:51, Bryce Dallas Howard (“Claire”) picks up a hardhat that clearly was not hard enough to prevent serious brain leakage in its former wearer. The trace is a sharply defined gouge that nearly cleaves the hardhat into two half-hats. This trace is either from a claw or tooth, but because it’s by itself, I’m going to surmise it was from a single strategically employed claw. How wide was the claw? We can figure that out by using the Bryce Dallas Howard Pollex Ratio™ (BDHPR) of 1.0, which assumes her thumb is the same width as mine, 2.2 cm (0.9 in). (Yes, I have petite thumbs. You have a problem with that?)

Based on this unit of measurement, the split seems to be at least three times her thumb width, or minimally 6.6 cm (2.6 in) wide. Which, incidentally, is about the same width as the scratches left on the concrete wall, which I also interpreted as coming from claws, and which neatly connects the escaped “dinosaur” to this heinous act committed on what was no doubt an out-sourced employee who did not have health insurance. Coincidence? No, it’s ichnology!

Jurassic-World-Hardhat-PunctureHey, this hardhat is defective! Let’s check the warranty. Yup, sure enough: “Does not cover hybrid dinosaur attacks.” But at least we got a cool trace out of it.

So despite all of the problems my paleontological colleagues justifiably noted for the dinosauroid animals depicted in the trailer, I am encouraged that Jurassic World will have enough ichnology in it to persuade me to leave a buttock-shaped impression on my theater seat in June 2015. But there had better be tracks, nests and feces in it, otherwise you’ll see my footprints going straight out of the theater.

(For other “ichnology at the movies” posts by Yours Truly, also check out The Ichnology of Pacific Rim and The Ichnology of Godzilla.)

Groovy Trace Fossils at the SVP

After an undramatic (but still tiring) trip from Atlanta, Georgia to Berlin, Germany, I’m happy to be attending the Society of Vertebrate Paleontology annual meeting (SVP) in Berlin. The meeting – with talks, posters, and various social events – officially begins today (Wednesday, November 5) and continues through Saturday, November 9, but like all good paleontology meetings, it also has field trips before and afterwards.

Aside from my being with more than a thousand other paleontologists, exchanging information about the latest research, and enjoying good German beer while learning about this research (all of these are connected, I assure you), one of the main reasons why I am so far from Georgia is to present some of my research, too. It’s very much in the preliminary stages, but my coauthors and I thought it would be good to put this work out for other paleontologists to examine, poke, prod, and otherwise leave their impressions on it before we present it in a formal, peer-reviewed paper. I’ll be providing pictures and words expressing our work in a poster session today.

Groovy-Trace-Fossils-Cedar-Mountain-FormationSeries of small grooves in an Early Cretaceous (about 100 million-year-old) sandstone in Arches National Park, Utah (USA). Notice how they make radiating patterns, too. Do you wonder what made these trace fossils? If so, join the club. My coauthors and I take a semi-educated guess, which is just below for your reading pleasure. (Photograph by Anthony Martin, taken in June 2012; scale in centimeters.)

The following abstract summarizes the work, but the preceding picture might help, as does this one-sentence summary at the start of the poster:

Linear grooves in Early Cretaceous sandstone beds of the Early Cretaceous (Aptian-Albian) Cedar Mountain Formation are likely feeding trace fossils made by a beaked vertebrate, such as a pterosaur or bird.

VERTEBRATE FEEDING TRACE FOSSILS IN THE CEDAR MOUNTAIN FORMATION (LOWER CRETACEOUS), ARCHES NATIONAL PARK, UTA (USA): BIRD, PTEROSAUR, OR UNKNOWN TRACEMAKER?

MARTIN, Anthony J., Emory University, Atlanta, GA, USA, 30322; KIRKLAND, James I., Utah Geological Survey, Salt Lake City, UT, USA; MILNER, Andrew R.C., St George Dinosaur Discovery Site at Johnson Farm, St. George, UT, USA; SANTUCCI, Vincent L., National Park Service, Washington, DC, USA.

ABSTRACT

Abundant linear grooves on sandstone bedding planes of the Ruby Ranch Member of the Cedar Mountain Formation (Lower Cretaceous) in Arches National Park (Utah, USA) are interpreted as feeding traces made by a beaked vertebrate, such as a bird or pterosaur. These grooves have regular lengths (15.7 ± 2.0 mm), widths (3.4 ± 0.3 mm), and depths (1.5 ± 0.7 mm; n = 30), indicating a common origin related to the behavior and anatomy of their tracemakers. The trace fossils are either: solitary, bundled together as parallel groups of 4-8 grooves, or form semi-circular to circular patterns of 35-70. Bundles forming arc-like patterns are 13-15 cm wide. Grooves are on the same surface with runzelmarken, invertebrate trails, tridactyl theropod tracks, and a didactyl dromaeosaurid track. Forms and patterns of these features do not correspond to any known inorganic structures or invertebrate traces, nor traces made by fish. Thus they are considered as trace fossils made by either birds or pterosaurs. Runzelmarken and laminations imply that algal films bound sedimentary surfaces and helped to preserve these trace fossils and their associated theropod tracks. Hence the grooves may have been grazing traces, in which tracemakers gouged just underneath and parallel to algal films by using hard body parts, such as beaks. If so, beaks would have been 3-4 mm wide and groove lengths would have been linked to beak length and neck movement. The diameter of the semicircular and circular patterns suggests that the tracemakers were relatively small vertebrates. Arc-like patterns of clustered grooves could have been made by the tracemaker standing in one spot or shifting laterally to systematically mine the surface. However, no pes tracks were observed in direct association with these grooves. Hence the traces also may have been formed.

Many thanks to my coauthors – Jim Kirkland, Andrew Milner, and Vincent Santucci – for their help on this research, which hopefully will get a little bit of the attention it deserves here in Berlin. Stay tuned this week for more ichnologically related posts, which I’ll try to write and publish in between all of the aforementioned enjoyable exchanges and German beer.

Traces of the Red Queen

The seagull looked peaceful on that beach, lying on its left side with its eyes closed. Yet it was a permanent quietude, as only its head was there.

This disembodied head stuck out as a white spot with a red edge, perched on top of a pile of dull-brown, dead cordgrass. The torso so recently connected to this head was nowhere to be seen, and I could find no tracks belonging to the gull or any other animal nearby. It looked as if it had been placed there as an object of art, ready for erudite admirers – wine glasses in hand – to comment on its broader themes and nuanced metaphors. To a ichnologist, though, it also spoke of a sudden death, and one likely dealt by a aerial predator.

Seagull-Head-Decapitated-WassawThe place where I saw this gruesome sign was on Wassaw Island, Georgia. Wassaw is the only island on the Georgia coast that was never logged or otherwise developed by European or Americans, hence it retains a more primitive feel compared to most other Georgia islands. You can only get there by boat, and in this instance our boat captain and guide – John Crawford – had taken our field-trip group there to learn about its unique natural history. Because of its intact environments and general lack of human influence on the landscape, I was not surprised to see something new on Wassaw. However, I haven’t seen anything like this since.

Within minutes of arriving on the island, this beheaded seagull presented a little mystery for us. As mentioned before, tracks and the rest of the body were not visible, nor were any droplets of blood around its head, either. Moreover, its dry feathers and the freshness of its fatal wound – a clean severing of its neck vertebrate – also meant it had not washed up on shore. Where did it die, and how did it get there?

After ruling out the land and sea, we looked above the beach, and realized that the attack must have been delivered up there, in the air. We then imagined what could have possessed the bulk, ferocity, and other means to chop through a seagull’s neck while in flight. The list of suspects was a short one, and we quickly narrowed it down to one: a bald eagle.

Our hypothesis was not so far-fetched, as bald eagles don’t just eat fish, but also kill and eat other birds, including gulls. This meant the seagull head we saw that morning was very likely a result of bird-on-bird predation. Extending this a bit further into the evolutionary pasts of these birds, it reflected a time when when their non-avian dinosaur ancestors killed and were killed by similar behaviors, but on the ground.

How did birds evolve flight from non-flighted theropod ancestors? No doubt one of many selection pressures exerted on non-avian dinosaurs was predation. Any means for increasing the likelihood of escape from predators also bestowed a greater probability for passing on genes coding for that “escaping trait” to the next generation of not-quite-flighted dinosaurs.

Of course, flight has evolved for many uses in birds. Nevertheless, making a quick getaway from mortal peril is still one of them. Yet flight has also been used as a means for enhancing predation in the birds that kill other birds, exerting new and different selection pressures on prey. This example of an evolutionary back-and-forth “arms race” between predators and prey is often nicknamed the Red Queen hypothesis, named after Lewis Carroll’s character in Alice in Wonderland. Only now I will change her line (said to a fleeing Alice) about running in place:

Now, here, you see, it takes all the running you can do to keep in the same place.

to a more avian-appropriate one:

Now, here, you see, it takes all the flying you can do to keep in the same place.

Still, In this Georgia-coast example, a more appropriate literary allusion would have been to the Queen of Hearts from Alice in Wonderland, a decapitating character famous for uttering the line, “Off with their heads!” In this sense, the Red Queen and Queen of Hearts meet in the arms race between predators and prey.

Will this “Red Queen of Hearts” scenario happen again during eagle and seagull conflicts? Yes: that is, unless the seagulls’ descendants adapt, which may be followed by the eagles’ descendants adapting to these changes. And on it goes, this evolution of the now blending with the then, a reminder that these days of the dead affect those of the living, as well as those not yet alive.

Slow Worms at Wormsloe

Every time I visit the Georgia coast, traces that have been there all along make themselves apparent to me for the first time. One would think these personal discoveries would stop happening after more than fifteen years (on and off) of going to that coast and studying its traces, especially after writing a 700-page book about them (Life Traces of the Georgia Coast). Nevertheless, they happen, and when they do, these insights underscore the importance of doing regular field work in the same places. However familiar it might seem, there’s always something different you missed previously while there. So before each trip to the Georgia coast, I make sure to become wide-eyed and expectant, rather than jaded and bored.

Intersecting-Worm-Trails-Wormsloe-1Mysterious trails in a sandy road, crossing and re-crossing paths. What could have made them? And why so many? If curious, read on. If not, I’ve heard there are some Web sites with pictures of cats that require your viewing. (Photo by Anthony Martin, taken at Wormsloe Historic Site, Georgia.)

The latest example of this exercise in place-based humility happened just a little more than a week ago during a short time at Wormsloe Historic Site, south of Savannah, Georgia. Sarah Ross, the President and Director of the Wormsloe Institute for Environmental History, invited me there to give a nature walk and talk to guests at a private event on the evening of Saturday, October 11. After the walk and talk (which was a big success), we all watched lovely and enlightening story-telling by a local Gullah/Saltwater Geechee performance group (The Saltwata Players), had a delicious dinner, partook in great conversations fueled by nice wine, and I got to sell and sign copies of the book I mentioned earlier. In short, the proverbial good time was had by all.

My wife Ruth and I stayed in a guest cabin on the grounds of the former plantation that night; in morning, I got up just before dawn to start tracking and otherwise looking for traces. In the dimness, only a few raccoon and deer tracks stood out on the sandy roads, as well as a pile of scat that had been inside a feral hog only a few hours before. A nearby salt marsh beckoned, and because the low tide had exposed its banks, I walked out onto a nearby dock for better views of its exposed surfaces. The dark mud was pockmarked by thousands of holes, most belonging to mud-fiddler crabs and other burrowing invertebrates that call this place home.

Salt-Marsh-WormsloeA small part of the salt marsh at Wormsloe Historic site where it abuts the maritime forest, and during low tide. See all of those holes in the foreground? I wonder what those might be?

Salt-Marsh-Wormsloe-BurrowsEach and every one of these holes is the burrow of a small marine-adapted animal – fiddler crabs, polychaete worms, and more. In other words, an ichnologist’s dream come true. (Photos by Anthony Martin.)

Less than a hundred meters from this dock is the home of Craig and Diana Barrow. Mr. Barrow is the ninth-generation heir of Wormsloe, but donated its grounds to the state of Georgia so that it could become a natural laboratory for researchers studying its environmental history. Ruth and I were acquainted with the Barrows from two previous visits to Wormsloe, and Craig – a great outdoors enthusiast – had eagerly given us personal tours of the woods, fields, and marshes on the property.

Having hunted for most of his life, Craig is a good tracker, and we’ve had in-depth discussions on animal-track forms, trackway patterns, aging of tracks, scat, and related topics. I find these conversations refreshing. Academic hierarchies, journal articles, impact factors, grant amounts, and other dull concerns become meaningless when you’re in the field with experienced naturalists. Here are some traces. Let’s learn.

Thus as the dawn light started to illuminate the maritime forest, I was not surprised to see Craig already outside his home, and to have him enthusiastically invite me to hop onto a golf cart with him to go look for tracks. He had already been out earlier on one of the sandy roads near his house and spotted three red foxes, so he wanted to check on whether their tracks were there, too. Within minutes, we arrived at the spot where he saw the foxes, and we quickly confirmed his sighting by identifying their fresh tracks in the loose sand on the road.

That was also about when Craig asked me a question that I answered wrong at first, then corrected once I gathered more data. You know, like any good scientist should. His question was “What’s this?”, and he was referring to a thin, shallow, and meandering groove in the sand. “Beetle trackway,” I answered instantly, without looking too closely. Then I squatted to show him the tiny tracks that would be on each side of the groove, where I imagined the beetle had dragged its abdomen.

Worm-Trail-Wormsloe-4Oh look, a beetle trackway, and right next to the tracks of a red fox (Vulpes vulpes)! How exciting! Gee whiz, I gosh-darn love science! Isn’t it neat? Wait a minute: what’s that earthworm doing at the end of a beetle trackway? (Photo by Anthony Martin, taken at Wormsloe Historic Site.)

That’s when I realized there were no tracks on either side of the groove. This was a trail made by a legless animal. “Wait a minute, this isn’t from a beetle,” I said. “Maybe a worm?” And by “worm,” I meant earthworm, but my small amount of experience with identifying earthworm traces made me a little uncomfortable with elaborating further on that idea. After all, I didn’t want to appear too ignorant about such common animals, and ones I had written about in both my book and on this blog (Of Darwin, Earthworms, and Backyard Science and Darwin, Worm Grunters, and Menacing Moles).

Fortunately, an earthworm saved me from further embarrassment by having the decency to be at the end of one of these trails, moving and otherwise actively demonstrating how these traces had been made. With our eyes and brains properly (and instantly) trained by this association between trace and tracemaker, Craig and I glanced around us. We were rewarded for looking, and promptly became astonished. The road was criss-crossed with hundreds of earthworm trails for as far as we could see, and most of them had living worms at their ends.

Even better, a few of these trails connected to open, small-diameter vertical burrows. My second insect-biased mistake of the morning was to initially identify these burrows as the shafts of halictid bee burrows. However, too many earthworm trails connected directly to these holes. Again, like any good scientist should in the face of contradictory evidence, I changed my mind. These traces were also from earthworms, and showed where the earthworms exited their subterranean homes.

Vertical-Burrow-Worm-WormsloeEarthworm burrow marking exactly where it left its home for the surface world, and intersecting a trail. (Photo by Anthony Martin, taken at Wormsloe Historic Site.)

What really surprised me, though, was the length and complexity of the trails. These were not simple meandering paths, but complicated records of earthworm decision making. These worms may have been slow, but their traces certainly weren’t dull.

Worm-Trail-Wormsloe-2This trail was made by one earthworm that moved from right to left. The pointed grooves on either side of the main trail are from where its “head” and “tail” ends probed the sand.

Worm-Turning-Wormsloe-1Here’s an earthworm in action, moving from right to left. Compare this to the next photo to see how movement of both its forward and rear ends changes the trail, putting newer traces on top of the previously made ones.

Worm-Turning-Wormsloe-2See what I mean? Small but multiple movements from both ends of a worm – as well as its middle – make this much, much more than just a “worm trail.” So don’t be calling it that. (Photos by Anthony Martin, taken at Wormsloe Historic Site.)

Yes, I know, there’s a bigger question that looms over all of this ichnological minutiae: Why were so many worms on top of the ground, instead of in it? What could have caused hundreds of them to leave their homes and risk the perils of dehydration and predation at the surface?

I speculated aloud that their mass stranding might have been related to vibrations imparted to the road. After all, Charles Darwin had noted how earthworms reacted like this to subsurface vibrations, associating these with their mortal enemies, burrowing moles. This was independently verified by “worm grunters” of the Appalachians, who took advantage of earthworm-mole co-evolution to get bait for their fishing. Craig backed up my idea by saying that he had grated the road the previous day. So perhaps the vibrations from his vehicle and activities had persuaded the earthworms to come up and out of the ground.

Later, though, I wondered whether another much larger stimulus had invoked such aversive reactions in the earthworms, one that persisted for more than a day after the road had been grated. What else could have done this, impelling these earthworms to flee, much like urban hipsters sensing the first few notes of a nearby Justin Bieber concert, and leaving spilled PBR’s in their wake?

Then it came to me. A full moon that weekend had caused higher tides than normal in the area, ranging from 2.6 to 2.9 m (8.5-9.6 ft). As a result, saltwater probably crept high enough in the soil profile to trigger a collective reaction in the earthworms, which do not fare well once salty water starts filling their homes. Yes, that would do it.

Salt-Marsh-WormsloeHi, terrestrial earthworms. Remember me? I’m a salt marsh with 2.5-3 m high tides, right next to where you live.

Assuming this hypothesis is correct, what we saw there on that sandy road of Wormsloe Historic site was a great example of a marine ecosystem forcing animals living in a terrestrial ecosystem to drastically change their behaviors. Best of all, these animals made a suite of traces that reflected this sudden change in their behaviors. If preserved in the fossil record, such trails and burrows might even be recognizable to geologists and paleontologists, some of whom are quite fond of calling every invertebrate trace fossil a “worm burrow” anyway.

All in all, this field experience at Wormsloe taught me a lesson about keeping my senses open to noticing and wondering about traces wherever I go, as should you, gentle readers. Look for those moments when the worm has turned: they will teach you something new.

Worm-Trail-Wormsloe-1

Vestiges of Home

I first became a scientist in my backyard. This path to life-long inquiry began when I was four years old, as soon as my family moved to a larger house, and one with a larger yard. This small, outdoor patch of land with a few large trees, bushes, and grass soon became my field area, laboratory, classroom, and all-purpose place for conducting experiments in nature. Even better, my proclivity for observing this world outside of myself was encouraged – or at least tolerated – by my mother and father.

At the time, I had no idea just how important of a role this backyard and parental support would play in my scientific career. Yet now I look back on it with a mix of gratitude and wistfulness, especially as both of my parents have departed this earth I have studied for most of my life.

Backyard-Home-IndianaHere’s where I first learned science by going into the field. Back in the day, people – including my parents – called it a “backyard.” (Photograph by Anthony Martin.)

Indiana was an odd place for a natural scientist to develop in the 1960s. I recall how kids in public schools there and then were encouraged to study and pursue careers in science. However, this was mostly because of the “space race,” in which the U.S. was competing against the U.S.S.R. to see who could first land on the moon. I loved space, staring at the moon, planets, and stars, and I watched Star Trek (the original series, of course), dreaming of some day traveling in space. Science fiction stories became an outlet for me as well. Weekly trips to the public library meant checking out books by Arthur C. Clarke, Ray Bradbury, and other sci-fi writers who expanded my perspectives and kick-started my imagination with worlds far different from those I could experience in the Midwest.

Yet science fiction wasn’t the only subject that put me on a first-name basis with librarians as I checked out stacks of books. There were two other topics that supplemented my learning, namely dinosaurs and insects. Although the study of dinosaurs had not yet gone through its major scientific revolution of the 1970s, these animals still loomed large in my and other children’s inner worlds. “Tyrannosaurus rex! Stegosaurus! Brontosaurus!” we kids would shout gleefully at one another, or at bemused adults. Books with artistic recreations of dinosaurs and the occasional movie starring dinosaurian protagonists – such as The Beast from 20,000 Fathoms, The Valley of Gwangi – fed our fancy, too.

Charles-Knight-PaintingPhoto of the original mural of Charles Knight’s ‘Triceratops and Tyrannosaurus‘ (1927), which is in the Field Museum of Natural History in Chicago, Illinois. While growing up, I saw this image many times in books, and it inspired both my artistic and scientific leanings. (Photograph by Anthony Martin.)

Still, no matter how hard I imagined, I could not see a tyrannosaur in my backyard, let alone watch it stalk and devour its prey. In contrast, insects and other animals with jointed legs delivered Tennyson’s “nature red in tooth and claw,” and much more. For about nine months of any given year during my childhood, starting in the spring, I could step out the back door of my house and watch ants, bees, wasps, butterflies, moths, spiders, and praying mantises. Plant-insect interactions in particular – such as pollination, herbivory, and wound responses in plants – drew me in, teaching me those ecological principles long before I ever heard the words “pollination,” “herbivory,” and “wound response.”

Roses-Pollination-Bee-HomeRoses blooming in the front yard of my Indiana home in August 2014, attracting a pollen-gathering carpenter bee (probably Xylocopa virginica). Female carpenter bees leave exquisitely crafted traces in wood, boring into them to make brooding cells, which they provision with pollen balls. The rose bush was originally planted by my father in the late 1970s. (Photograph by Anthony Martin.)

Leave-Insect-Feeding-TracesInsect damage on the leaf of an apple tree in the backyard of my Indiana home in August 2014. The leaf mine (left) was probably caused by a different insect from the one that made the incision along the leaf margin just to its right. Notice the brown discoloration in the leaf, a trace of its response to these injuries and its healing. My father planted this apple tree, but I’m not sure when: maybe also in the late 1970s. (Photograph by Anthony Martin.)

Predation fascinated me, probably because death was such an inappropriate topic for children to discuss with their parents. This wasn’t the artificial, acted-out stuff of TV and movies, but was in your face, or rather, in front of your face. With mild shame now (and apologies to my Buddhist friends), I remember going into my backyard, picking up ants, and throwing them into wolf spiders’ ground webs. It was a repeatable experiment in which I could observe spider response-times to tactile stimuli, and it was real.

My backyard is also where I learned to sit still and wait. As soon as I spotted a praying mantis, it was only a matter of time before that magnificent, big-eyed head swiveled to lock onto a target, moved delicately toward it, and sprang its barbed arms forward to snatch and hold its squirming dinner, which it devoured alive. Who the hell needed TV, with sharks, lions, and polar bears, when you had this, and for free?

Ah, there’s that word, “free.” This connects to the main reason why my science leaned more toward field observations and less to indoor labs, a legacy that stuck. You see, my family was poor. I didn’t know this until other kids at school made fun of my shoes, which had holes in their soles, or my pants, which were too outgrown or ragged, or my haircuts, which looked odd because my mother cut it, and badly, but with good intentions, because haircuts done by barbers were just too expensive. Compounding this (and not coincidentally), my mother and father never went to college, and my parents struggled to maintain their traditional roles, for which they were ill suited to succeed.

My father was a veteran of World-War II, and late in his shortened life was diagnosed with PTSD (post-traumatic stress syndrome), which in the 1970s was labeled “shell shock.” This condition meshed all too well with his alcoholism, meaning he had trouble keeping down a job for more than a few years. His last paycheck came from working as a night-shift janitor at a Columbia Records distribution center in Terre Haute. This job ended once he began suffering from a series of serious illnesses that put him in and out of hospitals for the last 15 years of his life. Only 59 years old, he died in the summer of 1985, just a few months before I left for Ph.D. study at the University of Georgia.

Dad-Then-LaterMy father at six months old (in 1927) and near the end of his life (circa 1982). His mother was still alive when the photo at the left was taken, but he never got to know her; she died when he was only two years old. During his last ten years of life, he developed a fondness for roses, cultivating them in our yard and bringing beauty to our home every year.

My parents were also Catholic, which in their time meant the only birth control they used was prayer. As a result, we had a big family, and I grew up with four brothers and one sister. But we were also reminded of unseen siblings, the ones who might have been. My mother was pregnant 13 times, with six successful births, but also six miscarriages and one stillbirth, meaning she bore more deaths than lives. Much later, I realized how this must have placed a profound emotional burden on her, even though she almost never mentioned it.

Judging from my mother’s affection for books and reading, I think she wanted to be an intellectual of sorts, perhaps even a scientist, or at least she wanted to learn and debate ideas with other people. This, however, was not possible when cleaning, cooking, shopping, paying bills, and otherwise taking care of six kids, all while constantly pregnant until she had her last child in 1962. Add to those demands a chain-smoking, alcohol-fueled, and narrow-minded husband who helped with none of those household tasks, followed by her being his in-house nurse and servant during the last 15 years of his life, and she didn’t stand a chance of reaching those ideals.

Dad-Back-From-War-with-MomHappier times for my parents, soon after my father came home after his service in the U.S. Army during World War II, where he fought in the Pacific. It would be his only trip abroad, but it scarred him for the rest of his life, which affected everyone around him. My mother never traveled outside of the U.S. and stayed in the Midwest for nearly all of her life.

Given such a family history, I experienced class differences and situations in college and graduate school that perplexed and occasionally stung. Even now, despite having taught at an elite private university for nearly 25 years, I still wrestle with imposter syndrome, and with how much my background sets me apart from others in my rarified academic world.

For instance, many of my academic colleagues are second-generation academics, or otherwise come from more socially elevated or well-to-do (or at least middle-class) families, where they never had to worry about paying the bills in time and making it through the month. Moreover, most of the students I’ve taught over the years have almost never experienced such economic anxieties, either. Behind all of the science I do and teach, and all of my achievements, I still hold onto a nagging, debilitating fear of scarcity, and a secret shame of how my family was on welfare and used food stamps to buy groceries. The taste of government cheese still lingers.

In the 1960s, education seemed like a way to escape from the cycle of poverty, and that was the message I constantly received from my mother and father. Sadly, that message sometimes translated as, “Don’t be failures like us.” Later in life, I turned that little frown upside down when I traveled, met wonderful people, and made scientific discoveries, many of which happened whenever I did field work in places far away from that backyard in Indiana.

Victoria-Coast-CretaceousIn grade school music class, I used to get in trouble for singing the chorus of Waltzing Matilda a bit too boisterously, which happened in between reading books about dinosaurs and insects. About 40 years later, I was walking along the coast of Victoria, Australia, looking for dinosaur tracks and insect trace fossils in the Cretaceous rocks there. Funny how that happens sometimes. (Photo by Ruth Schowalter.)

But here’s the thing about that whole “education helps people to escape from poverty” trope, one seemingly affirmed by my little personal story. This was much easier to do in the 1960s than today. The gap between the poor and rich in the U.S. today is the worst it’s been since the 1920s, with no sign of abating. People who wants to preach their faith-based mantra of “People just need to work harder to succeed” conveniently overlook that Horatio Alger was a second-generation Harvard man and Ayn Rand took government assistance. Also, an increased emphasis on student loans to pay for exploding tuition rates during the past 30 years has meant young, aspiring scientists may be starting their careers with crippling debt.

But here’s another thing: I was damned lucky because of my parents. Not despite them, but because of them. That’s what I say – and with considerable ferocity – every time someone tries to tell me (in a well-meaning way) how much my life reflects “the American dream.” For one thing, I grew up at a time when white boys were far more encouraged to go into science than African-American boys, or all girls. This accident of being born male, and in a family belonging to the dominant ethnic group of my culture, meant I benefited from the privilege of my gender and race, even as my socioeconomic background held me back.

Flagpole-ClimbingThat’s me, climbing a flagpole just outside my house when I was about seven years old, circa 1967. The rest of my family was standing below watching, cheering me on, and documenting the event. Little did I know at the time that other kids were told they couldn’t climb flagpoles, let alone make it to the top. Yes, that’s a metaphor. (P.S. The flagpole’s gone now.)

I also had lots of help along the way, such as financial aid and scholarships in college, and teaching assistantships in graduate school. This meant I didn’t have to take out student loans. Sure, I had less than $100 to my name the first month I began the teaching job I still hold (so far), but at least I began that job debt-free. Many of today’s aspiring scientists don’t have this luxury, and entrenched inequities related to gender and ethnicity continue to discourage careers in science for most Americans. Also, achieving a college degree today is nine times more likely if you come from an upper-income family than a poor one. It was never easy for poor people to become successful scientists, but it’s far, far tougher today. I was lucky.

Perhaps most importantly, though, I had parents who let me play outside and supported my learning science, however weird I must have seemed to them. I mean, staying out in the backyard for hours, flinging ants in spider webs, and watching praying mantises kill other insects? That was pretty strange, even in the 1960s. I even climbed trees in our backyard. I suspect that many of today’s “helicopter parents” would have forbidden a scrawny runt like me from going outside, let alone get my face close to spiders and insects, and handle unknown plants. Climbing trees probably would have involved first donning a series of ropes, carabiners, harnesses, padding, and a helmet, all while being supervised by a team of tree-climbing experts. Instead, like any arboreal primate should, I climbed those trees by myself, occasionally fell out of them, then got back up and climbed again. I was lucky.

Climbing-Pine-TreeMy favorite climbing tree in my backyard, which I started scaling when I was about six years old, so it must be more than 70 years old now. It was great fun to see how far I could get up into it and explore, and I found much peace just sitting in its crooks, watching the world below. Notice in the close-up (right) all of the scars on the trunk, marking the sites of the low-hanging branches, which fell off the tree a long time ago. (Yes, that’s another metaphor.)

My parents also regularly took me to our modest public library, where I checked out many books, which I read, and sometimes re-read. After my grade-school teachers alerted them that I was showing talent as an artist, my parents also spent some of their meager cash to buy me crayons, pencils, paper, acrylic paints, oil paints, and canvases as birthday and Christmas presents. So I drew and painted, and nature was my inspiration for such creations. I still can draw well – and sometimes teach drawing to my students – because of what my parents did for me. I was lucky.

Insects-Then-NowOne of my earliest attempts at scientific illustration (left), coupled with one of my more recent efforts (right). The one on the left – clearly intended as a multi-part figure – shows some of the insects I observed in my backyard, as well as some of the ecological interactions they had as pollinators, predators, and prey. The one on the right is from Figure 5.4a in Life Traces of the Georgia Coast (2013, Indiana University Press, p. 192), and is the subsurface form of a nest made by Florida harvester-ants (Pogonomyrmex badius); scale bar = 25 cm (10 in).

As I do field work today, I silently thank my father for taking me on hunting and fishing trips, effectively planting the seeds for my present-day comfort with forests, streams, lakes, and other outdoor environments. On those hunting trips, I learned what little my father knew then about tracking animals, a skill that I honed later in life, and now one of my passions. On fishing trips, I watched the behavior and ecology of freshwater crayfish, which abounded in the streams of southern Indiana. I had no clue that more than 40 years later I would reconnect with that childhood interest in crayfish by discovering the oldest fossil crayfish in Australia. I also did a different kind of fishing by studying and interpreting fish trace fossils, such as a trail left by a bottom-feeding fish about 50 million years ago in Wyoming. Then I combined my childhood love of insects and dinosaurs by writing and publishing a paper about Cretaceous insect cocoons near dinosaur nests in Montana. I didn’t see an ocean until I was 20 years old, but last year published a 700-page book, Life Traces of the Georgia Coast, which I also illustrated myself. None of those things would have happened without my parents’ help early in my life. I was lucky.

My father and mother did what they could with what life dealt them, and my mother in particular. She was born in northern Illinois and lived there through the Great Depression during her childhood. While there, she met her high-school sweetheart, who some day would be the father of her six children. He went off to fight in a world war, she waited for him to return, and they married soon afterwards. They headed south to Terre Haute, and lived in one house, then another. The latter was her home for 50 years.

Mom-Honeymoon-OutcropMy mother on her honeymoon at Turkey Run State Park in southern Indiana, 1947. While looking through a photo album in 2012, I was delighted to see this photo, showing her when she was fully in love with my father, but also enjoying what must have been a glorious waterfall. Best of all for me, though, it has an outcrop of Late Carboniferous (Pennsylvanian) Period deltaic sandstones in the background.

My mother outlived my father by nearly 30 years and got to see how her love of books, reading, and encouragement of my learning came back home to her. In 2001 and 2006, it was with much pride I mailed her each edition of a textbook I wrote and published (Introduction to the Study of Dinosaurs). In the preface to Life Traces of the Georgia Coast, I pointedly thanked her and my father for cultivating a childhood life filled with books, art, and the outdoors.

Mom-Then-LaterThe first and last photographs of my mother, when she was three years old (about 1929) and just last month, the latter photo taken by my brother Pat.

My mother died three weeks ago. The first stroke was toward the end of December 2013, and its treatment necessitated her going to a hospital, and then to assisted care. For the next eight months, she had a picture window that looked out onto a courtyard, where she watched the blooms, butterflies, and birds of what would be her last Indiana spring and summer. On August 26, she had a second and more deadly stroke, putting her in a coma that took away all of her speech, thoughts, and memories. After receiving emergency care in Terre Haute, she was evacuated by helicopter to an intensive-care unit in Indianapolis that same night. Six days later, she exhaled for the last time, less than a week shy of her 88th birthday.

Decatur-Book-Festival-Dedication-MomMe giving a talk about my most recent book, Dinosaurs Without Bones (2014) at the Decatur Book Festival last month. At the end of my talk, I dedicated it to my mother. Almost no one in the audience knew she was in a coma at the time, and none of us knew she would die three days later. (Photo by Ruth Schowalter.)

Just before this second stroke, I flew up to Indiana to see her, and we spent some time with our extended family, but also some quiet moments talking together, just mother and son. During this visit, I told her how much I appreciated everything she had done for me. We got to say goodbye to one another. We were lucky.

Today I am a trace of my mother’s and father’s love and care, and a trace of my home and backyard in Terre Haute, Indiana. Given more luck, I’ll be around for a while longer, leaving more traces of my own, and in many more places. Thank you, Dad. Thank you, Mom. You did good.

Mom-Me-Then-LaterFirst and last photos of my mother with me, separated by more than 50 years. As you can see from both pictures, my disposition hasn’t changed much. And thanks to Mom, it probably won’t.