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.

Cumberland Island, Georgia: Not a Barrier to Education

When learning about the natural sciences, there comes a time when just reading and talking about your topics in the confines of a classroom just doesn’t cut it. This semester, we had reached that point in a class I’m teaching at Emory University (Barrier Islands), in which we all needed a serious reality check to boost our learning. So how about a week-long field trip, and to some of the most scientifically famous of all barrier islands, which are on the coast of Georgia?

Last Friday, March 8, our excursion officially began with a long drive from the Emory campus in Atlanta, Georgia to St. Marys, Georgia. Fortunately, Saturday morning was much easier, only requiring that we walk across the street, step onto a ferry, and ride for 45 minutes to Cumberland Island. Cumberland was our first island of the trip, and the southernmost of the Georgia barrier islands. I have written about other topics there, including the feral horses that leave their mark on island ecosystems, the tracks of wild turkeys, and those marvelous little bivalves, coquina clams.

So rather than my usual loquacious ramblings, punctuated by whimsical asides, this blog post and others later this week will be more photo-centered and accompanied by mercifully brief captions. This approach is not only a practical necessity for proper time management while teaching full-time through the week, but also is meant to give a sense of the daily discoveries that can happen through place-based learning on the Georgia coast. I hope you learn with us, however vicariously.

After a 45-minute ferry ride to Cumberland Island, the students received a different sort of lecture when naturalist extraordinaire Carol Ruckdeschel – who is writing a book about the natural history of Cumberland Island – met with them and gave them a brilliant overview of the island ecology. She mostly talked with the students about the effects of feral animals on the island, then spent another hour with us in the maritime forest and through the back-dune meadows. It was a real treat for the students and me, and a great way to start the field trip.

A leaf-cutter bee trace! Despite my writing about these and illustrating them in my book, these distinctive incisions were the first I can recall seeing on the Georgia barrier islands. These traces were abundantly represented in the leaves of a red bay tree we spotted along a trail through the maritime forest, making for a great impromptu natural history lesson for the students.

A freshly erupted ghost shrimp burrow on the beach at Cumberland, in which the students were lucky enough to witness the forceful ejection of muddy fecal pellets by the shrimp from the top of its burrow. I mean, really: explain to me how the life of an ichnologist-educator can get any better than that?

The fine tradition a field lunch, made even more fine by the addition of fine quart sand to our meals, freely delivered by a brisk sea breeze. Did the sand leave any microwear marks on our teeth? I certainly hope so.

A student is delighted to test my ichnologically based method for finding buried whelks underneath beach sands, and find out that it is indeed correct. (Was there any doubt?) Here she is proudly holding a live knobbed whelk, which I can assure you she promptly placed back into the water once its photo shoot was finished for the day.

Just to join in the fun, other students decided my “buried whelk prospecting” method required further testing. Let’s just say this student did not disprove the hypothesis, but rather seemed to confirm it, and doubly so. It’s almost as if ichnology is a real science! (Yes, these whelks went back into the water, too.)

OK, enough about marine predatory gastropods (for now). How about some of the largest horseshoe crabs (limulids) in the world? We found a large deposit of their carapaces above the high-tide mark, some of which were probably molts, but others recently dead. Sadly, though, we did not see any of their traces. Bodies only do so much for me.

Where do dunes come from? Well, a mother and father dune love each other very much… No wait, wrong story. What happens is that dead cordgrass from the salt marshes washes up onto the beach, where it starts slowing down wind-blown sand enough that it accumulates. Now it just needs some wind-blown seeds of sea oats and other plants to start colonizing it, and next thing you know, dune. Dude.

Ah, a geological tradition in action: comparing actual sand from a real outdoor environment to the sand categories on a handy grain-size chart, and using a hand lens. It’s enough to bring a tear to the eyes of this geo-educator. Or maybe that was just the wind-blown sand.

Finally, something that really matters, like ichnology! This is a three-for-one special, too: sanderling feces (left), tracks, and regurgitants (right), the last of these also known as cough pellets. Looks like it had coquina and dwarf surf clams for breakfast.

Wow, more shorebird traces! The tracks are from a loafing royal tern, and it clearly needed to get a load off its mind before moving on with the rest of its day.

Tired of shorebird traces? How about a modern terrestrial theropod? Wild turkey tracks in the back-dune meadows of Cumberland were a happy find, leading to my grilling the students with the seemingly simple question, “What bird made this?” They did not do well on this, but hey, it was the first day, and at least no one said “robin” or “ostrich.”

Did somebody say “doodlebug?” This long, meandering, and collapsed tunnel of an ant lion (a larval neuropteran, or lacwing) tells us that this insect was looking for prey in all the wrong places.

Behold, tracks that bespeak of great, thundering herds of sand-fiddler crabs that used to roam the sand flats above the salt marsh. Where have they gone, and will they ever come back? Who knows where the males might be waving their mighty claws? Do the female fiddler crabs suffer from big-claw envy, or are they enlightened enough to reject cheliped-based hierarchies imposed upon them by fiddler-crab society? All good questions, deserving answers, none of which make any sense.

Yes, that’s right, feral horses are really bad for salt marshes. Between overgrazing and trampling, they aren’t exactly what anyone could call “eco-friendly.” My students had heard me say this repeatedly throughout the semester, and Carol Ruckdeschel said the same thing earlier in the day. But then there’s seeing it for themselves, another type of learning altogether.

And the day ended with beautiful ripple marks, beckoning from the sandflat below the boardwalk on our trip back onto the ferry. Even this ichnologist can appreciate the aesthetic appeal of gorgeous physical sedimentary structures.

What’s the next island? Jekyll, which is just north of Cumberland along the Georgia coast, visited yesterday. Stay tuned, and look for those photos soon.

Going Hog Wild on the Georgia Barrier Islands

(The following is the third part of a series about traces of invasive species of mammals on the Georgia barrier islands and the ecological effects of these traces. Here is an introduction to the topic, the first entry about the feral horses of Cumberland Island, and the second entry about the feral cattle of Sapleo Island.)

Anytime I hear someone refer to a Georgia barrier island as “pristine,” I wince a little bit, smile, and say, “Well, bless your heart.” The truth is, nearly every island on the Georgia coast, no matter how beautiful, is not in a pristine state, having been considerably altered by humans over the past 4,500 years, whether these were Native Americans, Europeans, or Americans. These varying degrees of change are sometimes subtle but nonetheless there, denoted by the loss of original habitats and native species or the addition of non-native species.

Still, one Georgia barrier island comes close to fulfilling this idealistic label: Wassaw Island, which during its 1,000-year geologic history somehow escaped commercial logging, agriculture, animal husbandry, and year-round settlements. Partially because of this legacy, Wassaw is designated as a National Wildlife Refuge, and is reserved especially for ground-nesting birds. One of the ways this island works well as a refuge for these birds is – as of this writing – its “hog free” status, a condition that can be tested with each visit by looking for the obvious traces of this invasive species.

The interior of Wassaw Island, with maritime forest surrounding a freshwater wetland created by alligators, the rightful owners of the island. On Wassaw, there are no tracks or signs of feral hogs, qualifying it as a “pristine” island. (Photograph by Anthony Martin.]

Contrast this with Cumberland Island National Seashore, where hogs run wild and freely. The huge pits here are in an intertidal zone of a beach on the northwest corner of the island. Naturalist Carol Ruckdeschel (background) for scale. (Photograph by Anthony Martin.)

Feral hogs (Sus scrofa) have a special place in the rogue’s gallery of invasive mammals on the Georgia barrier islands, and most people agree they are the worst of the lot. Hogs are on every large undeveloped island – Cumberland, Sapelo, St. Catherines, and Ossabaw – and they wreak ecological havoc wherever they roam. The widespread damage they cause is largely related to their voracious and omnivorous diet, in which they seek out and eat nearly any foodstuff, whether fungal, plant, or animal, live or dead. Their fine sense of smell is their greatest asset in this respect: every time I have tracked feral hogs, their tracks show head-down-nose-to-the-ground movement as the norm, punctuated by digging that uses a combination of their snouts and front hooves to tear up the ground in their quest for food. In other words, they generally act like, well, you know what.

Most importantly from the standpoint of native animals that try to live more than one generation beyond a single hog meal, feral hogs eat eggs. Hence ground-nesting birds and turtles are among their victims, and hogs are quite keen on eating sea turtle eggs. Mothers of all three species of sea turtles that nest on the Georgia coast – loggerhead (Caretta caretta), green (Chelonia mydas), and leatherback (Dermochelys coriacea) – dig subsurface nests filled with 100-150 eggs full of protein and other nutrients, making tempting targets for any free-ranging feral hogs. Similarly, hogs also threaten another salt-water turtle, the diamondback terrapin (Malaclemys terrapin); this turtle lays its eggs in shallow nests near the edges of salt marshes, which hogs manage to find. Conservation efforts to save diamondback terrapins from human predation have mostly succeeded (it used to be a tasty ingredient in soups), but hogs can’t read and don’t discriminate when it comes to eating eggs. Here is where feral hogs are particularly dangerous as an invasive species: unlike feral horses or cattle, which “merely” degrade parts of their ecosystems: feral hogs can contribute directly to the extinction of native species. As I often tell my students, if you want to cause a species to go extinct, stop it from reproducing.

Sea-turtle nest on Sapelo Island, marked by a stake and protected by plastic fencing to prevent feral hog and raccoon depredation of its eggs. An individual raccoon would only eat about 1/3 of the eggs in a sea-turtle nest, whereas pigs would just keep on eating. (Photograph by Anthony Martin.)

As an ichnologist, though, what astounds me the most about these hogs is the extremely wide ecological range of their traces. I have seen their tracks – often made by groups traveling together – in the deepest interiors of maritime forests, in freshwater wetlands, and crossing back-dune meadows, high salt marshes, coastal dunes, and beaches. If their traces became trace fossils, paleontologists would refer to them as a facies-crossing species, in which facies (think “face”) are the identifiable traits of a sedimentary environment preserved in the geologic record. Based on their tracks and sign, they are ubiquitous in terrestrial and marginal-marine environments. Oh, and did I mention they are also good swimmers? Swimming across a tidal channel at low tide is an easy feat for them, enabling hogs to spread from island to island, without the assistance of humans.

Run away, run away! Feral hogs in a St. Catherines Island salt marsh, consisting of two juveniles and an adult, do not stick around to see whether humans are going to shoot them; they just assume so. This sighting, along with their widespread tracks and other traces, show how feral hogs can occupy and affect nearly every environment on a Georgia barrier island. (Photograph by Anthony Martin.)

So to better understand why feral hogs are such successful invaders of the Georgia islands, it’s helpful to think about their evolutionary history. As expected, this history is complicated, just like that of any domesticated species in which selective breeding narrowed the genetic diversity we see today. About 15 subspecies of Sus scrofa have been identified, making its recent family tree look rather bushy. Based on genetic studies, divergence between wild species of Sus scrofa (so-called “wild boars”) and various subspecies may have happened as long ago as 500,000 years ago in Eurasia, although humans did not capture and start breeding them until about 9,000 years ago.

Depiction of a European wild boar from 1658, in The History of Four-Footed Beasts and Serpents by Edward Topsell. Original image from a woodcut, digital image in Wikipedia Commons here.

The closest extant relatives to these hogs native to North America are peccaries, which live in the southwestern U.S., Central America, and South America. However, peccaries are recent migrants to North America, and only one Pleistocene species (Mylohyus nasutus) is known from the fossil record of the eastern U.S. This means that the post-Pleistocene ecosystems of the eastern U.S., and especially those of the Georgia barrier islands, have never encountered anything like these animals. Also, unlike the feral horses of Cumberland Island and the feral cattle of Sapelo Island, the feral hogs of the Georgia barrier islands were likely introduced early in European colonization of the coast, and may have started with the Spanish in the 16th century.

Unfortunately, part of the selective breeding of Eurasian hogs was for early sexual maturity and large litter sizes. Female feral hogs can reach breeding age at 5 months, and litters typically have 4-8 piglets, but can be greater than 12; females also can produce three litters in just more than a year. Do the math, and that adds up to a lot of pigs in a short amount of time. Furthermore, on Georgia barrier islands with few year-round human residents, the only predation pressures young piglets face daily include raptors (no, not that kind of raptor) or alligators. This means young hogs reach sexual maturity soon enough to rapidly overrun a barrier island.

Feral hog trackway in a sandy intertidal zone of Cumberland Island, showing a typical gallop pattern (four tracks together –> space –> four tracks together), symbolizing how they are running roughshod over this and other islands. (Photograph by Anthony Martin.)

Yet as we have learned in North America, and particularly on the Georgia barrier islands, feral hogs rapidly revert to their Pleistocene roots. Similar to the feral cattle of Sapelo Island, these hogs are rarely seen by people, especially on islands where humans regularly hunt them. Every time I have spotted them on Cumberland, Sapelo, St. Catherines, or Ossabaw, they instantly turn around, briefly flash their potential pork loins and ham hocks, and flee. As anyone who has raised hogs can tell you, pigs are smart and learn quickly. Hence I imagine that after only one or two shootings of their siblings or parents, they readily associate upright bipeds with imminent death, especially if these bipeds are carrying boomsticks.” (Speaking of which, I know of at least one sea turtle researcher who does his part to decrease feral hog populations – while also feeding the local vultures – through his able use of such a baby-sea-turtle-protection device.)

Hence much of what we learn about these free-ranging pigs and their behaviors in the context of the Georgia barrier islands is from their traces. Among the most commonly encountered feral hog traces are:

• Tracks

• Rooting pits

• Wallows

• Feces

Feral hog tracks are potentially confused with deer tracks, as they both consist of paired hoofprints and overlap in their size ranges, which are about 2.5-6 cm (1-2.5 in) long. Nonetheless, feral hog tracks are less “pointed,” have nearly equal widths and lengths, rounded ends, and the two hoofs often splay. Two dew claws – vestigial toes – frequently register behind the hoofs, especially when hogs step into soft sand or mud or are running. Trackways normally show indirect register of the rear foot onto the front footprint in a diagonal walking pattern, but can also display a whole range from slow walk to full gallop patterns. With repeated use of pathways, trackways become trails, although I’m not sure if hogs are merely using and expanding previously existing whitetail deer trails, if they are blazing their own, or a combination of the two. (I suspect the last of these is the most likely.)

Feral hog tracks, showing nearly equal lengths and widths, rounded ends, and splaying of hooves, all three of which help to distinguish these from whitetail deer tracks. Scale in centimeters. (Photo by Anthony Martin, taken on Sapelo Island.)

Feral hog trackway on upper part of a sandy beach (moving parallel to shore), showing slow diagonal walking pattern, verified by hoof dragmarks between sets of tracks. Scale = 10 cm (4 in). (Photo by Anthony Martin, taken on St. Catherines Island.)

Rooting pits are broad but shallow depressions – as much as 5 m (16 ft) wide and 30 cm (1 ft) deep – that are the direct result of feral hogs digging for food. In most instances, I suspect they are going for fungi and plant roots, but they probably also eat insect larvae, lizards, small mammals, and any other animals that live in burrows. These pits are typically in maritime forests and back-dune meadows, but I have seen them in salt marshes and dunes, and, most surprisingly, in the intertidal areas of beaches. What are they seeking and eating in beach sands? I think anything dead and buried that might be giving off an odor. I have even seen their tracks associated with broken carapaces of horseshoe crabs (Limulus polyphemus), a menu item that never would have occurred to me if I had not seen these traces.

Rooting pit in back-dune meadow on St. Catherines Island. Former student, who answers to the parent-given appellation of “Andrew,” for scale. (Photograph by Anthony Martin.)

Evidence of feral hog feeding on a horseshoe crab (Limulus polyphemus). All I can say is, it must have been really hungry. (Photo by Anthony Martin, taken on St. Catherines Island.)

Wallows are similar in size and appearance to rooting pits, but have a different purpose, which is to provide hogs with relief from both the Georgia summer heat and biting insects that invariably go with this heat. These structures are often near freshwater wetlands in island interiors, but I’ve seen them next to salt marshes, too. If these wallows intersect the local water table, they also make for attractive little ponds for mosquitoes to breed, meaning these hog traces indirectly contribute to the potential spread of mosquito-borne diseases.

Wallow in maritime forest, Sapelo Island, with a standing pool of water indicating the local water table at the time. (Photo by Anthony Martin.)

Hog feces may look initially like deer pellets, but tend to aggregate in clusters. Most of the ones I have seen are filled with vegetation, but the extremely varied diets of feral hogs means you should expect nearly anything to show up in their scat.

Feral hog feces on Sapelo Island, which is more clumped than that of whitetail deer. Scale in centimeters. (Photo by Anthony Martin, taken on Sapelo Island.)

Which of these traces would make it into the fossil record? I would certainly bet on at least some of their tracks getting preserved, based on the sheer ubiquity of these traces in nearly every sedimentary environment of a Georgia barrier island. Other likely traces would be their pits and wallows, although their broad size and shallow depths would make them difficult to recognize unless directly associated with tracks. Feces would be the least likely to make it into the fossil record as coprolites, unless these contained a fair amount of bone or other mineralized stuff, which could happen with hogs.

What to do about these hogs, and how to decrease the impacts of their traces? Well, as most people know, pigs are wonderful, magical animals that were domesticated specifically for their versatile animal protein. So one solution is more active and year-round hunting of hogs, and using them to supplement breakfasts, lunches, and dinners of local residents on the Georgia coast, a neat blend of reducing a harmful feral species while encouraging a chic “locavore” label on such food.

However, the sheer numbers of hogs on some of the islands would likely require a more systematic slaughter to make a dent in their numbers, an approach that would probably deter any ecotourism unrelated to hog hunting. (Let’s just say that firearms and bird watching are an uneasy mix.) The introduction of native predators is another possible solution. For example, Cumberland Island has a population of bobcats (Lynx rufus) that was introduced primarily to control the whitetail deer population, but these cats probably also take a toll on the feral hogs (although how much is unknown). I have even heard suggestions of reintroducing red wolves (Canis rufus) to a few of the islands. These pack-hunting predators were native to the southeastern U.S. before their extirpation by fearful European settlers, and probably would reduce feral hog populations, but just how much of an impact they would have is hard to predict.

In summary, the feral horses, cattle, and hogs of the Georgia barrier islands have significant effects on the ecology and geology of the Georgia barrier islands, and will continue to do so until creative solutions are proposed and implemented to reduce and otherwise manage their numbers. In the meantime, though, these invasive species present opportunities for us to study their traces, learn more about their unseen behaviors, and compare these behaviors with their evolutionary histories. More science is always good, and in this respect, the Georgia barrier islands are the gifts that keep on giving.

Traces of feral mammals on Sapleo Island: feral hog tracks strolling past a piece of feral cattle scat in a sandy road next to a maritime forest. What is the fate of these invasive species on the Georgia barrier islands, and how will these environments continue to change because of their presence? (Photo by Anthony Martin, taken on Sapelo Island.)

Further Reading

Ditchkoff, S.S., and West, B.C. 2007. Ecology and management of feral hogs. Human-Wildlife Conflicts, 1: 149-151.

Giuffra, E., Kijas, J.M.H., Amarger, V., Carlborg, Ö., Jeon, J.-T., and Andersson, L. 2000. The origin of the domestic pig: independent domestication and subsequent introgression. Genetics, 154: 1785-1791.

Mayor, J.J., Jr., and Brisbin, I.L. 2008. Wild Pigs in the United States: Their History, Comparative Morphology, and Current Status. University of Georgia Press, Athens, Georgia: 336 p.

Taylor, R.B., Hellgren, E.C., Gabor, T.M., and Ilse, L.M. 1998. Reproduction of feral pigs in southern Texas. Journal of Mammalogy, 79: 1325-1331.

Wood, G.W., and Roark, D.N. 1980. Food habits of feral hogs in coastal South Carolina. The Journal of Wildlife Management, 44: 506-511.

Tracking the Wild Cattle of Sapelo Island

(The following is part of a series about traces of key invasive species of mammals on the Georgia barrier islands and the ecological effects of these traces. Here is an introduction to the topic from last month, and the first entry was about the feral horses of Cumberland Island.)

If I were pressed to name my favorite Georgia barrier island, it would be a tough choice, but it would be Sapelo. Many reasons support this preference, both practical and emotional, which I will relate before getting to the topic featured in the title.

Trails made by feral cattle traveling far into a salt marsh on Sapelo Island, Georgia. But I thought cows only stayed in grassy fields and chewed their cuds? Please read on. (Photograph by Anthony Martin.)

As I mentioned in a previous entry, Sapelo is an excellent place to take university students for teaching basic coastal ecology, geology, ichnology, and taphonomy. Many ecologists consider it as the birthplace of modern ecology, which happened in the 1950s and ‘60s, and it hosted studies that established many basic principles of neoichnology (the study of modern traces) in the 1970s and ‘80s. For the latter, one of the key figures was Robert (Bob) Frey, who was my Ph.D. advisor when I attended the University of Georgia. Sapelo’s human history is also fascinating, dating back to more than 4,000 years ago – evidenced by a prominent Native-American shell ring – and continues through today with Hog Hammock, the only Gullah (“saltwater Geechee”) community left on the Georgia coast.

I have been to Sapelo dozens of times, with or without students, and each time there, I continue to be surprised and delighted by some new observation that reveals itself to those with open eyes and minds. Thus it has everything a field-oriented scientist could want, especially one who likes to learn something different with each visit.

All of these facts and feelings, though, may also lend to an impression that Sapelo is an idyllic and ecologically “pure” place, a true slice of what a Georgia barrier island should aspire to be. Alas, it is not, and like other Georgia barrier islands, Sapelo has been ecologically altered because of exotic plants and animals introduced there during colonial and post-colonial times. Among these species, the most noteworthy on Sapelo is Bos taurus, the only population of wild cattle on any Georgia barrier island and one of the few in the continental U.S.

Unlike the feral horses on Cumberland Island, nearly everyone agrees on the origin of the wild cattle on Sapelo: they are most likely descended from domestic cattle released on the island by millionaire R.J. Reynolds, Jr. (of carcinogenic fame). Although the details are sketchy as to exactly when and why he did this, Reynolds, who owned most of Sapelo from 1933 until his death in 1964, let loose his dairy cows and bulls in the first half of the 20th century. Many generations of these cattle have bred in the wild since, and still roam the island in sufficient numbers to warrant some attention from wildlife biologists, ecologists, and others interested in learning about their behavior and impacts on the local ecosystems.

In my experience, though, the words “wild” and “cattle” are rarely used in everyday conversations about these animals that, through our domestication of them, provide us with milk, cheese, and meat. Ask someone to describe a cow, for instance, and most people will be unflattering: “slow,” “docile,” and “stupid” are among the most common adjectives applied, which is sometimes followed by a giggling reference to the Midwestern U.S. tradition of cow-tipping.

Thinking of tipping this cow? Be my guest, and be sure to forward the resulting video to Animal Planet for others’ lurid entertainment. The “cow” is actually a feral bull, and it was standing its ground at the edge of a field on Sapelo Island, fully aware that we spindly little bipeds were staring at it, and seemingly daring us to get closer. The poor quality of this photo is because I had my camera on maximum digital zoom: my momma didn’t raise no dumb kid. (Photograph by Anthony Martin.)

Yet these cattle are descended from wild species, aurochs (Bos primigenius) that survived the end-Pleistocene mass extinctions. You know, the same extinctions event that wiped out mammoths, mastodons, giant ground sloths, wooly rhinoceroses, saber-toothed cats, dire wolves, and other formidable megafauna of the Pleistocene. Hence aurochs must have had adaptive advantages over their Pleistocene cohorts. This was perhaps was related to their preferred ecosystems of wetland forests and swamps: remember that point with reference to Sapelo. Following the mass extinction, though, people in Eurasia, Africa, and India domesticated aurochs about 8,000 years ago. Through selective breeding, people came up with the present-day varieties we see of Bos taurus, which is considered a subspecies of B. primigenius.

Painting titled The Aurochs, by Heinrich Harder (1858-1935), probably made in 1920. Image is in the public domain and I found it on this Web site, authored by Peter Maas. Contrast how the artist depicted an auroch fighting off a pack of wolves with current expectations of how domestic cattle should behave in the face of pack-hunting predators, and you’ll get a better sense of the actual behaviors shown by wild cattle on Sapelo Island.

I am reminded of this evolutionary heritage whenever I go to Sapelo, because the cattle there are cryptic creatures of the maritime forest. Yes, that’s right: cryptic and living in the forest. A casual day-trip visitor to Sapelo will almost never see one, let alone any of several small herds that roam the island. Whenever an individual bull or herd is encountered in more open, grassy areas, they seemingly revert to Pleistocene behavior and slip into the woods, quickly concealing themselves from the prying eyes of humans. In short, they are not slow, docile, or stupid, and would never allow a person to get close enough to make an short-lived and ill-fated attempt to tip any of them.

This is about all you’ll see of a recent presence of the feral cattle on Sapelo Island: tracks, and if you are lucky enough to sight one, it will leave a lot more tracks and sign for you to study than that all-too-brief glimpse. Scale is in centimeters, and look closely where the slightly smaller the rear-foot track (manus) registered directly on top of the fron-tfoot (pes) track. (Photograph by Anthony Martin.)

Hence any meaningful study of these cattle and their ecological effects on Sapelo requires the use of – you guessed it – ichnology. Consequently, I have tracked these cattle, sometimes with my students and sometimes by myself, during many visits there. Although these tracking forays have generated many anecdotal yarns of yore about these “wild cows of mystery” worth retelling, I will reluctantly restrict myself here to summarizing their traces and the effects of these traces on the landscapes of Sapelo.

Traces of feral cattle on Sapelo consist largely of their tracks, trails or otherwise trampled areas, feces, and chew marks. In my experience, the vast majority of their traces are on the northern half of the island, although herds or individual bulls will occasionally leave their marks in the southern half when they graze on grassy areas there.

Tracks made by these feral cattle are unmistakable when compared to those of any other hoofed animal on Sapelo – such as white-tailed deer or feral hogs – which is a function of their greater size. Tracks are shaped like robust, upside-down Valentine’s hearts, with two bilaterally symmetrical hoof impressions rounded in the front and back. Tracks are normally about 9-14 cm (3.5-5.5 in) long, although I have seen newborn calf tracks as small as 5-6 cm (2-2.3 in) long; track widths are slightly less (by about 20%) than lengths. These cattle, like deer, spend much of their time walking slowly, so their rear-foot (pes) impressions often overlap behind their front-foot (manus) impressions, but can also overprint in direct register. Trackways typically show a diagonal-walking pattern, although these can be punctuated by frequent “T-stops,” in which tracks form a “T” pattern, with the top of the “T” made by the front feet whenever a trackmaker stopped.

Near-perfect direct register of smaller rear foot into front-foot tracks made by adult feral cow, recorded in exquisite detail in fine-grained sand. Scale in centimeters. (Photograph by Anthony Martin, taken on Sapelo Island.)

Because these cattle, for the most part, obey herding instincts, they habitually follow one another along the same narrow pathways through maritime forests and salt marshes, resulting in well-worn trails that wind between live oaks in forest interiors or cut straight across marshes. Nonetheless, the cattle also like to use the open freeways provided by the sandy roads that criss-cross much of the northern part of the island, which makes tracking them much easier, especially after a hard rain has “cleaned the slate.” When using a road, the cattle break single file and walk parallel or just behind one another, indicated by their overlapping and side-by-side trackways. On forest trails, they often drag their hooves across the tops of logs downed along trails, chipping and otherwise breaking down the wood.

Feral cattle tracks showing different sizes – and hence age structures – of the cattle, with some trackways overlapping (following one another) and some parallel, taking up the entire width of a sandy road on the north end of Sapelo Island. (Photographs by Anthony Martin, composite of three stitched together in Photoshop™.)

Log on feral-cattle trail, showing chipped wood on surface where hooves dragged across the top, possibly over generations of trail use. White-tailed deer do a similar behavior on their trails, but do not cause such obvious traces. (Photograph by Anthony Martin, taken on Sapelo Island.)

OK, here’s a reminder of something I just said and showed in a photo earlier: these cattle also form trails that wind deeply into the salt marshes. Why? Turns out that instead of restricting themselves to a terrestrial-only diet, they are eating smooth cordgrass (Spartina alterniflora), which grows abundantly in the marshes. This feeding results in their leaving many other traces, such as near-ground-level cropping of Spartina with clean tears, accompanied by considerable trampling of grazed areas. Although I was surprised to discover this for myself several years ago, people who raised cattle on the island in the 19th and early 20th centuries, perhaps through necessity, knew about this alternative foodstuff and fed it to cattle as a substitute for hay. Sure enough, historical references verify the use of smooth cordgrass as part of their diet (of the cattle, not the people, that is).

Evidence that feral cattle of Sapelo walk into salt marshes as a herd and eat the smooth cordgrass (Spartina alterniflora) there, based on trampling and overgrazing. Michael Bauman, who was an Emory undergraduate student at the time, for scale. (Photographs by Anthony Martin.)

Close-up of traces left on smooth cordgrass from feral cattle grazing, which are at various heights according to the level of their grazing activity. (Photograph by Anthony Martin, taken on Sapelo Island.)

Of course, among the most obvious traces these cattle leave in their wake are the end products of digestion (pun intended), feces. These “cow patties” vary in size depending on both the size of the tracemaker and liquid content of the scat. The bigger the tracemaker and the greater the water content to the plants, the wider the patties, which can exceed dinner-plate size. Similar to the situation on Cumberland Island with its feral horses and their feces, the native dung beetles must not be able to keep up with such a bounty, as I see many unrecycled, dried patties throughout the island, and have nearly stepped on freshly dropped pies that showed no signs of having been discovered by caring dung-beetle mothers.

Looks like cow scat. Smells like cow scat. Feels like cow scat. Tastes like cow scat. Good thing we didn’t step in it! But notice that the tracemaker did, leaving a bonus trace (track) on top of its impressive pile. (Photograph taken by Anthony Martin, taken on Sapelo Island.)

Given that the northern part of the island has extensive salt marshes flanking the maritime forest, and places with fresh-water sloughs containing more wetland plants, it makes sense that the cattle would stay mostly in that half of the island. The absence of humans on the north end of the island – other than occasional deer hunters, Department of Natural Resources personnel, or crazy ichnologists – is also a plus, as these cattle avoid people whenever possible.

But how does any of this relate to geology and paleontology? Well, because these feral cattle interact so much with Sapelo salt marshes, I actually included these animals as marginal-marine tracemakers in my upcoming book (Life Traces of the Georgia Coast, just in case you needed reminding). This places these bovines in the same category as feral horses – which negatively affect coastal dunes and salt marshes – and feral hogs, which even go into the intertidal zones of beaches for their foraging.

The biggest difference between the cattle and these other two hoofed species, though, is their impact on the marshes. In all of my years of noting cattle tracks and other sign on Sapelo, I have never seen evidence of their going to the beach, or even to the coastal dunes. Instead, they stay in the forests and wetlands, whether the latter are fresh-water or salt-water ones. This possibly reflects how the cattle, within just a few generations, switched back to auroch behaviors of the Pleistocene, preferring to live in wooded wetlands instead of in the terrestrial grasslands we modern humans keep forcing them to graze.

Thus any paleontologists looking into the fossil record of aurochs or their ancestral species – whether of body fossils or trace fossils – might use these present-day clues when prospecting for fossils. This serves as a great example of why I urge paleontologists to pay attention to invasion ecology and conservation biology, in which “ecologically impure” invasive species give us valuable insights on their evolutionary histories.

What else can we learn about these feral cattle and their ecological and geological impacts on Sapelo, especially through studies of their traces? For one, knowing the actual number of cattle on the island would be useful, as their quantity surely relates to how well the island ecosystems can handle present and future populations. But probably more important than this would be better defining their behaviors in the context of these non-native ecosystems. How to do this with a species that stays hidden so well, one that has apparently reverted to a Pleistocene way of life? Fortunately, behaviors can be defined through the ichnological methods I have outlined here. These methods can then easily augment others normally used by conservation biologists, such as trail cameras and direct observation.

Once this is done, we will know much more about these wild cattle than before, and will no longer have to rely on whispered legends of the mysterious bovines of Sapelo Island. Regardless, there is certainly still room for such stories, perhaps even artwork, operas, plays, movies, and music. Cattle have played such an integral role in the development of humanity, there is every reason to suppose that, as long as they continue to live on Sapelo, they and their traces will continue to intrigue us.

Further Reading

Ajmone-Marsan, P., Fernando Garcia, J., and Lenstra, J.A. 2010. On the origin of cattle: how aurochs became cattle and colonized the world. Evolutionary Anthropology, 19: 148-157.

Bailey, C., and Bledsoe, C. 2000. God, Dr. Buzzard, and the Bolito Man: A Saltwater Geechee Talks about Life. Doubleday, New York: 334 p.

McFeeley, W.S. 1995. Sapelo’s People: A Long Walk into Freedom. W.W. Norton, New York: 200 p.

Sullivan, B. 2000. Sapelo Island (GA): Images of America. Arcadia Publishing,  Mt. Pleasant, South Carolina: 128 p.

Teal, M., and Teal, J.M. 1964. Portrait of an Island. Atheneum, New York: 167 p. [reprinted by University of Georgia Press, Athens, in 1997: 184 p.]

Alien Invaders of the Georgia Coast

(This is the first in a series of posts about invasive species on the Georgia barrier islands, their traces, the ecological impacts of these traces, and why people should be aware of both their traces and impacts.)

Paleontologists like me face a challenge whenever we study modern environments while trying to learn how parts of these environments might translate into the geologic record. Sure, we always have to take into account taphonomy (fossil preservation), through which we acknowledge that nearly none of the living and dead bodies we see in a given environment will become fossilized; relatively few of their tracks, trails, burrows, or other traces are likely to become trace fossils, either.

Because of this pessimistic (but realistic) outlook, paleontologists often rub a big eraser onto whatever we draw from a modern ecosystem, telling ourselves what will not be there millions of years from now. We then retroactively apply this concept – a part of actualism or, more polysyllabically, uniformitarianism – to what happened thousands or millions of years ago. When paleontologists do this, they assume that today’s processes are a small window through which we can peer, giving insights into processes of the pre-human past.

Feral horse (Equus caballus) tracks crossing coastal dunes on Cumberland Island, Georgia. During their evolutionary history, horses originated in North America and populations migrated to Asia, but populations in North America went extinct during the Pleistocene Epoch about 10,000 years ago. Using the perspective of geologic time, then, could someone argue that horses are actually “native,” and these feral populations are restoring a key part of a pre-human Pleistocene landscape? (Photograph by Anthony Martin.)

However, a huge complication in our quest for actualism is this reality: nearly every ecosystem we can visit on this planet is a hybrid of native and alien species, the latter introduced – intentionally or not – by us. Thus when we watch modern species behaving in the context of their environments, we always need to always ask ourselves how non-native species have cracked the window through which we squint, through the past darkly.

This theme is considered in Charles C. Mann’s most recent book, 1493: Uncovering the New World Columbus Created, in which he argues how nearly all terrestrial ecosystems occupied by people were permanently altered by the rapid introduction of exotic species worldwide following Columbus’s landfall in the Western Hemisphere. Going even further back, though, the introduction of wild dogs (dingoes) into mainland Australia by humans about 5,000 years ago irrevocably changed the environments of an entire continent. Examples like these show that European colonization and its aftermath in human history during the last 500 years was not the sole factor in the spread of non-native species, and hints at how species invasions have been an integral part of humanity and its movement throughout the world.

Something tells me we’re not in Georgia any more. A male-female pair of dingoes (Canis lupus dingo) pose for a picture in Kakadu National Park, Northern Territory, Australia. Although now considered “native,” dingoes are an example of an invasive species that had a huge impact once brought over by people from southeast Asia about 5,000 years ago. For one, its arrival is linked to the extinction of native carnivorous mammals in the mainland Australia, such as thylacines (Thylacinus cynocephalus) and Tasmanian devils (Sarcophilus harrisii). (Photograph by Anthony Martin.)

Well-meaning (but deluded) designations of “pristine,” “untouched,”and “unspoilt” aside, the Georgia barrier islands are no exception to alien invaders. Moreover, like many barrier-islands systems worldwide, they differ greatly from island to island in: which species of invaders are there; numbers of individuals of each species; and the degree of how these organisms impact island ecosystems and even their geological processes.

Feral cat tracks in back-dune meadows of Jekyll Island, Georgia. Jekyll is one of the few Georgia barrier islands with a significant human presence year-round, hence these cats are descended from domestic cats that were either purposefully or accidentally let loose by residents. What impact do these cats have on native species of animals and ecosystems, and are these effects comparable to those of other invasive species on other islands? Scale = 15 cm (6 in). (Photograph by Anthony Martin.)

This is one of the reasons why I devoted several pages of my upcoming book, Life Traces of the Georgia Coast, to the traces of invasive species – tracks, trails, burrows, and so on – despite their failing an “ecological purity test” for anyone who might prefer to focus on native species and their traces. With regard to invasive species, the genie is out of the bottle, so we might as well study what is there, rather than apply yet another metaphorical eraser to species that are drastically shaping modern ecosystems and affecting the behavior of native species, thus likewise altering their traces.

A large pit of disturbed sand in a back-dune meadow caused by feral hogs (Sus crofa) on St. Catherines Island, Georgia. Because feral hogs are wide-ranging omnivores with voracious appetites, they cause considerable alterations to island habitats, from maritime forests to intertidal beaches. How do these traces affect the behavior and ecology of other species, especially native ones, in such a broad range of environments on the Georgia barrier islands? Can their traces actually alter the geological character of the islands? (Photograph by Anthony Martin.)

What are some of these invasive species? What makes for an “invasive species” versus a mere “exotic species”? How do the traces of invasive species affect native species on the Georgia barrier islands, and the ecology and geology of the islands themselves? And how do paleontologists and geologists figure into the study of invasive species?

These are all questions that I hope to explore in upcoming weeks here, and for the sake of simplicity, I will showcase an invasive species of mammal and its traces each week. Some of the photos shown here serve as a visual teaser of the invasive species and their traces that will be covered: feral horses (Equus caballus), cattle (Bos taurus), hogs (Sus crofa), and cats (Felis domestica). Yes, I know, there are many others, but these four are among the most ecologically significant species, they consist of animals that nearly everyone knows, and – best of all – they make easily identifiable traces. So these fours species will provide a starting point in our learning how the Georgia barrier islands can be used as case studies in the traces and ecological effects of traces made by invasive species.

Trail made by feral cattle (Bos taurus) cutting through a salt marsh and extending to the horizon, providing a clue of how this forest-dwelling animal can travel deeply into and affect marginal-marine environments. How might such traces show up in the geologic record, and was there a species that might have made similar traces on the islands in the recent past? (Photograph by Anthony Martin.)

Shorebirds Helping Shorebirds, One Whelk at a Time

How might the traces of animal behavior influence and lead to changes in the behavior of other animals, or even help other animals? The sands and the muds of the Georgia barrier islands answer this, offering lessons in how seemingly inert tracks, trails, burrows, and other traces can sway decisions, impinging on individual lives and entire ecosystems, and encourage seemingly unlikely partnerships in those ecosystems. Along those lines, we will learn about how the traces made by laughing gulls (Larus altricilla) and knobbed whelks (Busycon carica) aided sanderlings (Calidris alba) in their search for food in the sandy beaches of Jekyll Island.

A roughly triangular depression in a beach sand on Jekyll Island, Georgia, blurred by hundreds of tracks and beak-probe marks of many small shorebirds, all of which were sanderlings (Calidris alba). What is the depression, how was it made, and how did it attract the attention of the sanderlings? Scale = size 8 ½ (men’s), which is about 15 cm (6 in) wide. (Photograph by Anthony Martin.)

Last week, we learned how knobbed whelks (Busycon carica), merely through their making trails and burrows in the sandy beaches of Jekyll Island, unwittingly led to the deaths of dwarf surf clams (Mulinia lateralis), the latter eaten by voracious sanderlings. Just to summarize, the dwarf surf clams preferentially burrowed around areas where whelks had disturbed the beach sand because the burrowing was easier. Yet instead of avoiding sanderling predation, the clustering of these clams around the whelks made it easier for these shorebirds to eat more of them in one sitting. Even better, this scenario, which was pieced together through tracks, burrows, and trails, was later verified by: catching whelks in the act of burying themselves; seeing clams burrow into the wakes of whelk trails; and watching sanderlings stop to mine these whelk-created motherlodes of molluscan goodness.

Before and after photos, showing how the burrowing of a knobbed whelk caused dwarf surf clams to burrow in the same small area (top), which in turn provided a feast for sanderlings (bottom); the latter is evident from the numerous tracks, peak-probe marks, and clam-shaped holes marking where these hapless bivalves formerly resided. (Both photographs by Anthony Martin, taken on Jekyll Island, Georgia.)

Was this the only trace-enhanced form of predation taking place on that beach? By no means, and it wasn’t even the only one involving whelks and their traces, as well as sanderlings getting a good meal from someone else’s traces. This is where a new character – the laughing gull (Larus altricilla) – and a cast of thousands represented by the small crustaceans – mostly amphipods – enter the picture. How these all come together through the life habits and traces these animals leave behind is yet another example of how the Georgia coast offers lessons in how the products of behavior are just as important as the behavior itself.

Considering that knobbed whelks are among the largest marine gastropods in the eastern U.S., it only makes sense that some larger animal would want to eat one whenever it washes up onto a beach. For example, seagulls, which don’t need much encouragement to eat anything, have knobbed whelks on their lengthy menus.

So when a gull flying over a beach sees a whelk doing a poor job of playing “hide-and-seek” during low tide, it will land, walk up to the whelk, and pull it out of its resting spot. From there, the gull will either consume the whelk on the spot, fly away with it to eat elsewhere (“take-out”), or reject it, leaving it high and dry next to its resting trace. An additional trace caused by gull predation might be formed when gulls carry the whelk through the air, drop them onto hard surfaces – such as a firmly packed beach sand – which effectively cracks open their shells and reveals their yummy interiors.

Paired gull tracks in front of a knobbed whelk resting trace, with the whelk tracemaker at the bottom of the photo. Based on size and form, these tracks were made by laughing gulls (Larus altricilla). The one on the left is likely the one that plucked the whelk from its resting trace, as its feet were perfectly positioned to pick up the narrow end of the whelk with its beak. The second gull might have seen what the first was doing and arrived on the scene soon afterwards, hoping to steal this potential meal for itself. For some reason, though, neither one ate it; instead, they discarded their object of desire there on the sandflat. For those of you who wondered if I then just walked away after taking the photo, I assure you that I threw the whelk back into water. At the same time, though, I acknowledged that the same sort of predation and rejection might happen again to that whelk with the next tidal cycle. Other shorebird tracks in the photo are from willets and sanderlings. (Photograph by Anthony Martin, taken on Jekyll Island.)

Sure enough, on the same Jekyll Island beach where we saw the whelk-surf clam-sanderling interactions mentioned last week, and on the same day, my wife Ruth Schowalter and I noticed impressions where whelks had incompletely buried themselves at low tide, only to be pried out by laughing gulls. Although we did not actually witness gulls doing performing, we knew it had happened because their paired tracks were in front of triangular depressions, followed by more tracks with an occasional discarded (but still live) whelk bearing the same dimensions as the impression.

My wife Ruth aptly demonstrates how to document seagull and whelk traces (foreground) while on bicycle, no easy feat for anyone, but a cinch for her.  Labels are: GT = gull tracks; WRT = whelk resting trace; KW = knobbed whelk; SU = spousal unit; and LCEFV = low-carbon-emission field vehicle. (Photograph by Anthony Martin, taken on Jekyll Island, Georgia.)

With this search image of a whelk resting trace in mind, we then figured out what had happened in a few places when we saw much more vaguely defined triangular impressions. These were also whelk resting traces, but they were nearly obliterated by sanderling tracks and beak marks; there was no sign of gulls having been there, nor any whelk bodies. Hence these must have been instances of where the gulls flew away with their successfully acquired whelks to drop them and eat them somewhere else. But why did the sanderlings follow the gulls with the shorebird equivalent of having a big party in a small place?

Yeah, I did it: so what? A laughing gull, looking utterly guiltless, stands casually on a Jekyll Island beach, unaware of how its going after knobbed whelks also might be helping its little sanderling cousins find amphipods. (Photograph by Anthony Martin.)

Although many people may not know this, when they walk hand-in-hand along a sandy Georgia beach, a shorebird smorgasbord lies under their feet in the form of small bivalves and crustaceans. The latter are mostly amphipods (“sand fleas”), which through sheer number of individuals can compose nearly 95% of the animals living in Georgia beach sands. Amphipods normally spend their time burrowing through beach sands and eating algae between sand grains or on their surfaces.

Close-up view of the amphipod Acanthohaustorius millsi, one of about six species of amphipods and billions of individuals living in the beach sands of the Georgia barrier islands, all of which are practically begging small shorebirds to eat them. Photo from here, borrowed from NOAA (National Oceanic and Atmospheric Administration – a very good use of U.S. taxpayer money, thank you very much) and linked to a site about Gray’s Reef National Marine Sanctuary, which is about 30 km (18 mi) east of Sapelo Island, Georgia.

Because amphipods are exceedingly abundant and just below the beach surface, they represent a rich source of protein for small shorebirds. But if you really want to make it easier for these shorebirds to get at this food, just kick your feet as you walk down the beach. This will expose these crustaceans to see the light of day, and the shorebirds will snap them up as these little arthropods desperately try to burrow back into the sand. This, I think, is also what happened with the gulls pulling whelks off the beach surface. Through the seemingly simple, one-on-one predator-prey act of a gull picking up a whelk, it exposed enough amphipods to attract sanderlings, which then set off a predator-prey interaction between the sanderlings and amphipods, all centered on the resting trace of the whelk.

Two whelks near one another resulted in two resting traces, and now both are missing, which likely means they were taken by laughing gulls. Notice how all of the sanderling trampling and beak marks have erased any evidence of the gulls having been there. (Photograph by Anthony Martin, taken on Jekyll Island.)

So as a paleontologist, I always ask myself, how would this look if I found something similar in the fossil record, and how would I interpret it? What I might see would be a dense accumulation of small, overlapping three-toed tracks – with only a few clearly defined – and an otherwise irregular surface riddled by shallow holes. The triangular depression marking the former position by a large snail, obscured by hundreds of tracks and beak marks, might stay unnoticed, or if seen, could be disregarded as an errant scour mark. The large gull tracks would be gone, overprinted by the many tracks and beak marks of the smaller birds.

Take a look again at the scene shown in the first photograph, and imagine it fossilized. Could you piece together the entire story of what happened, even with what you now know from the modern examples? I’m sure that I couldn’t. Scale bar = 15 cm (6 in). (Photograph by Anthony Martin.)

Hence the role of the instigator for this chain of events, the gull or its paleontological doppelganger, as well as its large prey item, would remain both unknown and unknowable. It’s a humbling thought, and exemplary of how geologist or paleontologist should stop to wonder how much they are missing when they recreate ancient worlds from what evidence is there.

Cast (reproduction) of a dense accumulation of small shorebird-like tracks from Late Triassic-Early Jurassic rocks (about 210 million years old) of Patagonia, Argentina. These tracks are probably not from birds, but from small bird-like dinosaurs, and they were formed along a lake shoreline, rather than a seashore. Nonetheless, the tracemaker behaviors may have been similar to those of modern shorebirds. Why were these animals there, and what were they eating? Can we ever know for sure about what other animals preceded them on this small patch of land, what these predecessors eating, and how their traces might have influenced the behavior of the trackmakers? (Photograph by Anthony Martin; cast on display at Museo de Paleontológica, Trelew, Argentina.)

Another parting lesson that came out of these bits of ichnological musings is that all of the observations and ideas in this week’s and last week’s posts blossomed from one morning’s bicycle ride on a Georgia-coast beach. Even more noteworthy, these interpretations of natural history were made on an island that some scientists might write off as “too developed” to study, its biota and their ecological relationships somehow sullied or tainted by a constantly abundant and nearby human presence. So whenever you are on a Georgia barrier island, just take a look at the life traces around you, whether you are the only person on that island or one of thousands, and prepare to be awed.

Further Reading

Croker, R.A. 1968. Distribution and abundance of some intertidal sand beach amphipods accompanying the passage of two hurricanes. Chesapeake Science, 9: 157-162.

Elbroch, M., and Marks, E. 2001. Bird Tracks and Sign of North America. Stackpole Books. Mechanicsburg, Pennsylvania: 456 p.

Grant, J. 1981. A bioenergetic model of shorebird predation on infaunal amphipods. Oikos, 37: 53-62.

Melchor, R. N., S. de Valais, and J. F. Genise. 2002. The oldest bird-like fossil footprints. Nature, 417:936938.

Wilson, J. 2011. Common Birds of Coastal Georgia. University of Georgia Press, Athens, Georgia: 219 p.

The Lost Barrier Islands of Georgia

The Georgia coast is well known for its historic role in the development of modern ecology, starting in the 1950s and ongoing today. But what about geologists? Fortunately, they were not long behind the ecologists, starting their research projects on Sapelo Island and other Georgia barrier islands in the early 1960s. Indeed, through that seminal work and investigations afterwards, these islands are now renown for the insights they bestowed on our understanding of sedimentary geology.

Why would geologists be attracted to these islands made of shifting sand and mud that were nearly devoid of anything resembling a rock? Well, before sedimentary rocks can be made, sediments are needed, and those sediments must get deposited before solidifying into rock. So these geologists were interested in learning how the modern sands and muds of the barrier islands were deposited, eroded, or otherwise moved in coastal environments, a dynamism that can be watched and studied every day along any Georgia shoreline. The products of this sediment movement were sedimentary structures, which were either from physical processes – such as wind, waves, or tides – or biological processes, such as burrowing. Hence sedimentary structures can be classified as either physical or biogenic, respectively.

Cabretta Beach on Sapelo Island at low tide, its sandflat adorned with beautiful ripples and many traces of animal life. Sand is abundant here because of a nearby tidal channel and strong ebb-tide currents that tend to deposit more sand than in other places around the island. This sand, in turn, provides lots of places for animals that live on or in the sand, making trails and burrows, demonstrating how ecology and geology intersect through ichnology, the study of traces.  Speaking of traces, what are all of those dark “pipes” sticking out of that sandy surface? Hmmm… (Photograph by Anthony Martin.)

These geologists in the 1960s were among the first people in North America to apply what they observed in modern environments to ancient sedimentary deposits, and just like the ecologists, they did this right here in Georgia. For example, in 1964, a few of these geologists – John H. Hoyt, Robert J. Weimer, and V.J. (“Jim”) Henry – used a combination of: geology, which involved looking at physical sedimentary structures and the sediments themselves; modern traces made by coastal Georgia animals; and trace fossils. Through this integrated approach, they successfully showed that the long, linear sand ridges in southeastern Georgia were actually former dunes and beaches of ancient barrier islands.

These sand ridges, barely discernible rises on a mostly flat coastal plain, are southwest-northeast trending and more-or-less parallel to the present-day shoreline. Remarkably, these ridges denote the positions of sea-level highs during the last few million years on the Georgia coastal plain. The geologists applied colorful Native American and colonial names to each of these island systems – Wicomico, Penholoway, Talbot, Pamlico, Princess Anne, and Silver Bluff – with the most inland system reflecting the highest sea level. So how did these geologists figure out that a bunch of sand hills were actually lost barrier islands? And what does this all of this have to do with traces and trace fossils?

Map showing positions of sand ridges that represent ancient barrier islands, with each ridge marking the fomer position of the seashore. The one farthest west (Wicomico) represents the highest sea level reached in the past few million years, whereas the current barrier islands reflect an overlapping of two positions of sea level, one from about 40,000 years ago (Silver Bluff), and the other happening now. (Photograph by Anthony Martin, taken of a display at the Sapelo Island Visitor Center.)

Here’s how they did it. They first observed modern traces on Georgia shorelines that were burrows made by ghost shrimp, also known by biologists as callianassid shrimp. On a sandy beach surface, the tops of these burrows look like small shield volcanoes, and a burrow occupied by a ghost shrimp will complete that allusion by “erupting” water and fecal pellets through a narrow aperture.

Top of a typical callianassid shrimp burrow, looking much like a little volcano and adorned by fecal pellets, which coincidentally resemble “chocolate sprinkles,” but will likely disappoint if you do a taste test. (Photograph by Anthony Martin, taken on St. Catherines Island.)

A couple of ghost shrimp, which are either a male-female pair of Carolina ghost shrimp (Callichirus major) or a Carolina ghost shrimp and a Georgia ghost shrimp (Biffarius biformis). Sorry I can’t be more accurate, but I’m an ichnologist, not a biologist (although I could easily play either role on TV). Regardless, notice they have big claws, which they use as their main “digging tools.” The tracemakers look a little displeased about being outside of their protective burrow environments, but be assured I thanked them for their contribution to science, and promptly threw them back in the water so they could burrow again. Scale = 1 cm (0.4 in) (Photograph by Anthony Martin, taken on St. Catherines Island, Georgia.)

Just below the beach surface, these interior shafts widen considerably, making these burrows look more like wine bottles than volcanoes. This widening accommodates the ghost shrimp, which moves up and down the shaft to irrigate its burrow by pumping out its unwanted feces (understandable, that) and circulating oxygenated water into the burrow. Balls of muddy sand reinforce the burrow walls like bricks in a house, stuck together by shrimp spit, and the burrow interior is lined with a smooth wall of packed mud.

A small portion of a ghost-shrimp burrow, showing its wall reinforced by rounded pellets of sand and stuck together with that field-tested and all-natural adhesive, shrimp  spit. Photograph by Anthony Martin, taken on Sapelo Island.

Amazingly, these shafts descend vertically far below the beach, as much as 2-3 meters (6.5-10 feet) deep. Here they turn horizontal, oblique, and vertical, and tunnels intersect, branch, and otherwise look like a complex tangle of piping, perhaps reminding baby-boomers of “jungle gyms” that they used to enjoy as children in a pre-litigation world. Who knows what goes on down there in such adjoining ghost-shrimp burrow complexes, away from prying human eyes?

The deeper part of a modern ghost-shrimp burrow, exposed by erosion along a shoreline and revealing the more complex horizontally oriented and branching networks. Gee, do you think these burrows might have good fossilization potential? (Photograph by Anthony Martin, taken on Sapelo Island.)

See all of those burrow entrances on this sandy beach? Now imagine them all connecting in complex networks below your feet the next time you’re walking along a beach. Feels a little different knowing that, doesn’t it? (Photograph by Anthony Martin, taken on Sapelo Island.)

Interestingly, these burrows are definitely restricted to the shallow intertidal and subtidal environments of the Georgia coast, and their openings are visible at low tide on nearly every Georgia beach. Hence if you found similar burrows in the geologic record, you could reasonably infer where you were with respect to the ancient shoreline.

I think you now know where this is going, and how the geologists figured out what geologic processes were responsible for the sand ridges on the Georgia coastal plain. Before doing field work in those area, the geologists may have already suspected that these sandhills were associated with former shorelines. So with such a hypothesis in mind, they must have been thrilled to find fossil burrows preserved in the ancient sand deposits that matched modern ghost-shrimp burrows they had seen on the Georgia coast. They also found these fossil burrows in Pleistocene-age deposits on Sapelo Island, which helped them to know where the shoreline was located about 40,000 years ago with respect to the present-day one. This is when geologists started realizing that the Georgia barrier islands were made of both Pleistocene and modern sediments as amalgams of two shorelines, and hence unlike any other known barrier islands in the world.

Vertical shaft of a modern ghost-shrimp burrow eroding out of a shoreline on Cabretta Beach, Sapelo Island. Scale in centimeters. (Photograph by Anthony Martin.)

Vertical shaft of a fossil ghost-shrimp burrow eroding out of an outcrop in what is now maritime forest on Sapelo Island, but we know used to be a shoreline because of the presence of this trace fossil. Scale in centimeters. (Photograph by Anthony Martin.)

Geology and ecology combined further later in the 1960s, when paleontologists who also were well trained in biology began looking at how organisms, such as ghost shrimp, ghost crabs, marine worms, and many other animals changed coastal sediments through their behavior. So were these scientists considered geologists, biologists, or ecologists? They were actually greater than the sum of their parts: they were ichnologists. And what they found through their studies of modern traces on the Georgia barrier islands made them even more scientifically famous, and these places became recognized worldwide as among the best for comparing modern traces with trace fossils.

Further Reading:

Hoyt, J.H., and Hails, J.R. 1967. Pleistocene shoreline sediments in coastal Georgia: deposition and modification. Science, 155: 1541-1543.

Hoyt, J.H., Weimer, R.J., and Henry, V.J., Jr. 1964. Late Pleistocene and recent sedimentation on the central Georgia coast, U.S.A. In van Straaten, L.M.J.U. (editor), Deltaic and Shallow Marine Deposits, Developments in Sedimentology I. Elsevier, Amsterdam: 170-176.

Weimer, R.J., and Hoyt, J.H. 1964. Burrows of Callianassa major Say, geologic indicators of littoral and shallow neritic environments. Journal of Paleontology, 38: 761-767.

Georgia Salt Marshes: Places Filled with Traces

The Georgia coast has long captured the attention of scientists interested in its biological and geological systems and how these two realms overlap. For example, starting in the 1950s, ecologists – people who study the connections between living and non-living things in ecosystems – began investigating the exchange of energy and matter between the plants and animals of the Georgia barrier islands. In particular, they were interested in the Georgia salt marshes, most of which are between the mainland and the upland portions of the barrier islands. Why study salt marshes in Georgia, and not somewhere else? And how do the traces of plants and animals in these marshes, such as root disturbances, scrapings, burrows, and feces, actually play a major role in the functioning of these ecosystems?

The muddy bank of a tidal creek in a typical salt marsh on St. Catherines Island, Georgia. See the traces? No? It’s a trick question: it’s made of nothing but traces. Photograph by Anthony Martin.

Georgia salt marshes are flat, extensive coastal “prairies” dominated by a tall, marine-adapted grass, smooth cordgrass (Spartina alterniflora) in their lowermost parts. These ecosystems turned out to be fantastic places for scientists to study basic principles of ecology, and are among the most productive of all ecosystems, besting or equaling tropical rain forests in this respect. Georgia salt marshes also represent about one-third of all salt marshes in the eastern U.S. by area. How did this happen?

Such an unusual concentration of salt marshes along the relatively small Georgia coastline is a result of several factors. One is its semi-tropical climate, only rarely dipping below freezing, which allows marsh plants and animals to thrive and actively participate in their ecosystems nearly year-round. Another is the high tidal range of the Georgia coast of about 2.5-3 meters (8-10 feet), which causes enormous amounts of organic material – living and nonliving – to get cycled in and out of the marshes by this moving water.

A third reason, and perhaps the most important, is what people did not do to the marshes, which was to develop them in ways that would have completely altered their original ecological characters. (Take a look at the barrier islands of New Jersey as examples of what could have happened in Georgia.) Salt marshes that were not drained, filled in, paved over, or otherwise irreparably altered could be studied for what they were, not what we supposed.

Salt marsh and tidal creek adjacent to a maritime forest on Cumberland Island. Fortunately, this is a typical sight on the Georgia barrier islands, which gladdens ecologists and lots of other people who prefer to see their landscapes unpaved.

The scientists interested in the Georgia salt marshes, among them Eugene (“Gene”) Odum, Mildred Teal, and John Teal, were astonished by the amount of organic matter produced in these marshes, especially in their lower parts, which were appropriately called low marsh. Amazingly, much of this flux is controlled by tides and just five species of organisms you can easily see any given day in these marshes:

  • Smooth cordgrass (Spartina alterniflora)
  • Ribbed mussels (Geukensia demissa)
  • Eastern oysters (Crassostrea virginica)
  • Marsh periwinkles (Littoraria irrorata)
  • Mud fiddler crabs (Uca pugnax)

Just to oversimplify matters, but to assure that you get the big picture, the flow of matter and energy goes like this. Smooth cordgrass is the primary producer of organic material in the salt marshes, converting sunlight into food for it and, as it turns out, lots of other organisms. This is relatively easy for these plants because they are powered by intense Georgia sunlight much of the year. Smooth cordgrass also has extensive and complicated root systems, which help to hold most of the marsh muds in place when marshes are flushed by the tides. These roots locally change the chemistry of the surrounding mud and otherwise leave visible traces of their deeply penetrating networks, which are noticeable long after the plants had died and decayed.

Cross-section of a relict salt marsh preserved on Sapelo Island, Georgia, buried for about 500 years but just now being exhumed by shoreline erosion. See how deeply those roots of smooth cordgrass (Spartina alterniflora) penetrate the mud and still hold it in place? Modern ones do the same thing. Scale = 15 cm (6 in).

What produces the mud in a marsh? Mostly the ribbed mussels, oysters, and similar suspension-feeding animals, which: suck in water made cloudy by suspended clays; consume any useful organics that might be in that water; and excrete massive amounts of mud-filled feces, packaged with mucous as sand-sized particles. The oysters, along with cordgrass roots, stabilize the banks of tidal creeks, keeping these from washing away with each ebb tide.

If you’ve ever wondered what ribbed mussel (Geukensia demissa) feces look like, you’re in luck. Each one is only about 1 millimeter (0.04 inches) across, which makes them behave more like sand instead of much tinier clay particles. Also think of them as little packets of mud shrink-wrapped by mucous. Illustration by Anthony Martin, based on a figure by Smith and Frey (1985).

A view of what used to be a marsh surface – the relict marsh on Sapelo Island, that is – with stubs of long-dead smooth cordgrass accompanied by equally long-dead clusters of ribbed mussels (Geukensia demissa). Back in the day (about 500 years ago), these mussels were happily pumping out mud-filled feces, and their modern descendants are still doing the same thing. Sandal (left) is size 8½ (mens). Photograph by Anthony Martin.

Prominent clumps of eastern oysters (Crassostrea virginica), exposed at low tide in the middle of a tidal creek on Sapelo Island. These not only help to produce mud, but keep it in place, while also slowing down flow and helping to deposit mud. Photograph by Anthony Martin.

A close-up look at more oysters surrounded by smooth cordgrass, with both working together to bind and accumulate mud on Sapelo Island. Now that’s ecological teamwork! Photograph by Anthony Martin.

Both the cordgrass and oysters also baffle and otherwise slow down the water flow, causing mud – fecal or otherwise – to get deposited. In short, a Georgia salt marsh with its thick deposits of beautifully dark, rich, gooey mud, much of which consists of the traces of mussels and oysters, would cease to exist without these bivalves and smooth cordgrass, and would become more like an open lagoon.

Meanwhile, marsh periwinkles are constantly moving up and down the stalks and leaves of the smooth cordgrass, grazing on algae growing on the cordgrass. This activity causes visible damage to the plants, tearing them into small bits and pieces that fall onto the marsh surface.

Marsh periwinkles (Littoraria irrorata) doing what they do best, which is graze on the stalks and leaves of smooth cordgrass, leaving many traces from damaging these plants while also contributing plant debris to the marsh surface. Photograph by Anthony Martin, taken on Sapelo Island.

Fungi and bacteria further break down this “gentle rain from heaven” of cordgrass debris once it reaches the marsh surface. Here, mud fiddler crabs consume this stuff, along with any algae that might be growing on marsh surfaces. Their scrape marks and discarded balls of processed sediment are everywhere to be seen on the marsh surface and add to the sediment load of a marsh. Furthermore, as we may have learned in grade school, all animals poop, so in this way these fiddler crabs and other species of crabs living in the salt marshes donate even more enriched organic material. They also dig millions of burrows, some adorned by prominently pelleted turrets, churning the uppermost part of the marsh mud like earthworms would do to a soil in a forest or field.

Mud fiddler crabs (Uca pugnax) and their many traces on a salt marsh surface, including feeding pellets, scrape marks, and burrows. Photo by Anthony Martin, taken on Sapelo Island.

Mud-fiddler crab burrows exposed at low tide in a marsh, many with pellet-lined turrets. Why do they make these structures? Good question, which I’ll try to answer in the future. Photo by Anthony Martin, taken on Sapelo Island.

Hence you cannot go to a Georgia salt marsh and say, “I can’t see any traces,” unless you are closing your eyes or are otherwise sight deprived. The entire salt marsh is composed of traces, and these traces, which are the products of plant and animal behavior, actually control the ecology of the salt marshes. Thus I often refer to Georgia salt marshes as examples of “ichnological landscapes,” places that are the sum of all traces. This concept then better prepares us for viewing these and other Georgia coastal environments as places where geologists can begin to understand how organisms can leave their marks – both big and small – in the geologic record.

Further Reading:

Craige, B.J. 2001. Eugene Odum: Ecosystem Ecologist and Environmentalist. University of Georgia Press, Athens, Georgia: 226 p.

Odum, E.P. 1968. Energy flow in ecosystems; a historical review. American Zoologist, 8: 11-18.

Odum, E.P., and Smalley, A.E. 1959. Comparison of population energy flow of a herbivorous and a deposit-feeding invertebrate in a salt marsh ecosystem. Proceedings of the National Academy of Sciences, 45: 617-622.

Smith, J.M., and Frey, R.W. 1985. Biodeposition by the ribbed mussel Geukensia demissa in a salt marsh, Sapelo Island, Georgia. Journal of Sedimentary Research, 55: 817-825.

Teal, J.M. 1962. Energy flow in the salt marsh ecosystem of Georgia. Ecology, 43: 614-624.

Teal, J.M., and Teal, M. 1983. Life and Death of a Salt Marsh. Random House, New York: 274 p.

Teal, M., and Teal, J.M. 1964. Portrait of an Island. Atheneum, New York: 167 p. [reprinted by University of Georgia Press in 1997, 184 p.]

Why Study Traces in Georgia? A Celebration of the Familiar

For those of us who live in Georgia, we either forget or don’t know about the ecological and geological specialness of this part of the U.S. For example, my undergraduate students here in Atlanta often talk dreamily about their desire to visit the Amazon River basin, Costa Rica, Kenya, Australia, or other places far removed from Georgia, beguiled as they are by the exotic “other” qualities of those places with their biota and landscapes. On the other hand, almost none of these students have been to the Okefenokee Swamp, the Blue Ridge Mountains, the Cumberland Plateau, the long-leaf pine forests of Ichauway, or the Georgia barrier islands, unless my colleagues or I have taken them there on field trips. Yet these places, especially those with freshwater ecosystems, collectively hold a biodiversity nearly matching that of the Amazon River basin, an evolutionary consequence of the long geologic history of the Appalachian Mountains.

To be fair, I have likewise found myself succumbing to such place-based deflection and lack of appreciation for what is more-or-less in my backyard. In 2001, I realized that I had been to Brazil (three times) more often than Fernbank Forest (two times), even though Fernbank was only a five-minute bicycle ride from home in Decatur, Georgia. This imbalance was soon corrected, though, and many visits later, I learned to appreciate how this old-growth southern Appalachian forest in the middle of metropolitan Atlanta is a gem of biodiversity, every native species of plant and animal a facet testifying to their long evolutionary histories. Still, I wonder why we often ignore what is nearby, even if it is extraordinary?

Related to this quandary is one of the most common questions I encountered from friends, family, and colleagues while writing my book – Life Traces of the Georgia Coast – which was, “Why are you, a paleontologist and geologist, writing about the traces of modern plants and animals in Georgia?” This is a legitimate inquiry, but my answer surprises most people. I tell them that my main reason for staying here in Georgia to study the tracks, trails, burrows, nests, and other traces of its barrier islands is because these traces and their islands are world-class and world-famous. This high quality is directly linked to the biodiversity of the Georgia barrier islands, but also their unique geological histories compared to other barrier-island systems. Furthermore, these islands have inspired more than a few major scientific discoveries related to modern ecology and geology, some of which, made nearly 50 years ago, are still applicable to diagnosing the fossil record and the earth’s geologic history. In short, the Georgia barrier islands and their traces also reflect a legacy recognized by scientists far outside the confines of Georgia.

How so? I’ll explain in upcoming posts, and hope to demonstrate how the marvelous ecosystems of the Georgia coast and its geological processes are the proverbial gift that keeps on giving, continually helping us to better understanding the earth’s geologic past. Now that’s special!

Burrows at dawn: a partial view of the thousands of ghost-shrimp burrows dotting a Georgia beach at low tide, their entrances looking like tiny volcanoes. What makes these burrows so important, scientifically speaking, and why are they something that would cause scientists from outside of Georgia to travel and see in person? Photo by Anthony Martin and taken on Sapelo Island, Georgia.