I’ve always been a big fan of aquariums. Having grown up in the landlocked Midwest and not seeing an ocean with its bountiful life until I was 20 years old, I am still drawn to the old-school charm of big tanks filled with salt water and populated by exotic fish and other sea critters. These environments, however artificial, never fail to inspire awe and wonder. Even better, they often teach me something new and relevant each time I pay closer attention to what they hold.
A seahorse, of course, is not a horse. But that’s not the only way seahorses differ from horses, in that they leave trails instead of tracks. Intrigued? Yeah, me too. (Photograph by Anthony Martin, taken at the UGA Aquarium, Skidaway Island, Georgia.)
Nonetheless, I also have a “problem,” which manifests itself whenever I’m at an aquarium, walking along a beach, sitting on a park bench, driving down a road, or, well, conscious. As an ichnologist, I’m constantly looking for animal traces. Then once found, I study these traces carefully so that they may inform me whenever I see similar traces in the fossil record. But because I’m a land-dweller and rarely have the opportunity to snorkel or scuba-dive, aquariums come in handy for observing traces of aquatic animals I might not often see. Particularly helpful are aquariums in which the people caring for them were kind enough to include sand on their bottoms (the aquariums, that is).
So last weekend, while leading a class field trip to the Georgia coast and after a wonderful boat ride to Wassaw Island and back, I eagerly joined my students in viewing a salt-water aquarium. This particular venue was the UGA Aquarium (UGA = University of Georgia, Athens) is maintained by the UGA Marine Extension Service (MAREX) on Skidaway Island, Georgia. Our visit was especially satisfying because we were there on a Sunday afternoon, when the aquarium is closed to the public. This luxury afforded us plenty of room and quietude, qualities that are rumored to enhance learning.
Within just a few minutes of entering the main room, one tank to the right caught my eye, and not just because of its pretty colors, but for its denizens and traces on the sandy bottom of that tank. It contained seahorses, fishes that are so odd compared to other fishes, we humans had to compare them to hoofed domesticated mammals. The best part of all, though, was that this tank had lots of intersecting grooves and circular imprints on its sandy surface, which no doubt had been made by the seahorses.
A seahorse (Hippocampus sp.) showing off its lack of swimming skills by moving along the sandy bottom of a tank. Gee, what are all of those meandering and intersecting grooves in the sand and circular imprints? I wonder what made those? Sorry, first guess doesn’t count. (Photograph by Anthony Martin, taken at the UGA Aquarium, Skidaway Island, Georgia.)
All seahorses are under the genus Hippocampus, which consists of more than fifty species. Evolutionarily speaking, they are ray-finned fish (actinopterygians) and share a common ancestor with pipefish and sea dragons (Sygnathidae). The oldest known fossil seahorses are in Miocene Epoch rocks, from about 13 million years ago. Besides their equine-like profiles, they are well known for their prehensile tails, which can either grasp onto algae, sponges, or corals, or curl up underneath them as they swim.
However, seahorses are never going to inspire bets at underwater race tracks, as they are among the slowest-swimming of fish, propelled mostly by tiny pectoral fins while moving upright. Still, they don’t need to be fast, as they are very successful predators, with about 90% accuracy in nabbing fast-swimming small crustaceans that get too close to their mouths. Seahorses also don’t need to swim away from larger predatory fishes that might wish to pick them from a seafood menu. Whenever seahorses attach to algae and corals, they sway in harmony with their temporary hosts, effectively blending in with their surroundings.
One point I keep in mind whenever visiting an aquarium, zoo, or other such enclosures is how these can alter so-called “normal” behaviors of their animals. In this instance, the smaller space of this tank, combined with little material for attachment, meant these seahorses were more likely to swim along its bottom then they might in an open ocean. Accordingly, they had made lots of traces in the sand: mostly undulating grooves, but a few circular impressions from their curled tails plopping onto one side or the other.
A seahorse making tail trails while swimming along the bottom of an aquarium. Notice how the trail would become less linear, wider, and more circular if the tail flops over to one side or another, involving a greater area of the curled end. (Photograph by Anthony Martin, taken at the UGA Aquarium, Skidaway Island, Georgia.)
A close-up of those trails left by swimming seahorses dragging their tails along a sandy surface. Also, check out the overlapping circular “plop” traces on the right, made by the curled part of the tail? (Photograph by Anthony Martin, taken at the UGA Aquarium, Skidaway Island, Georgia.)
What’s the take-home message of these observations for ichnologists, geologists, and paleontologists? That experience matters, as does questioning preconceived notions about what we might observe from the geologic record. Take a look at the preceding photo, and tell me – quite honestly – that your very first interpretation of the tracemakers would have been “fish,” let alone “seahorse.” Instead, I think nearly everyone (yes, me too) would have reached for the easiest answer, which would have been “worm trails,” similar to how geologists reflexively apply “worm burrows to anything small, tubular trace fossil they encounter at an outcrop. Wrong, wrong, wrong.
So next time when looking at rocks formed in marine environments – whether from the last 13 million years or much older – and these rocks host lots of “worm trails” on their surfaces, ask yourself who else could have made such trails, and how. Reach beyond easy and ordinary explanations, and imagine. Oh, and when you go to aquariums, don’t just look at their sea-life, but also the traces of the sea-life in them.
The wide variety of modern bird behaviors – as well as the traces that result from these behaviors – continue to captivate and fascinate me. Given recent revelations of birds’ dinosaurian ancestry and the interrelationships of modern birds (an evolutionary history spanning more than 150 million years), this wonderment should be expected. Accordingly, then, the traces made by modern birds can be equally varied, and can serve as guides to the behaviors of their predecessors, especially when made by birds interacting with ecological margins (ecotones).
A mixture of tracks left by boat-tailed grackles (Quiscalus major) and American crows (Corvus brachyrhynchos) on wind ripples in the upper part of a sandy beach. So if paleontologists found something similar in the geologic record, would they be able to say more than “Looks like a bunch of birds were walking around”? That’s why we look at modern traces and their associated behaviors: to get beyond such easy (and terribly incomplete) answers. (Photograph by Anthony Martin, taken on Tybee Island; pen is about 15 cm (6 in) long.)
The most recent example I witnessed of bird tracemakers and their traces in an ecotone setting was last month on Tybee Island (Georgia). Tybee is a barrier island just east of Savannah, and one I had visited in May, when I noted burrowing wasps in the coastal dunes there. The tracemakers were boat-tailed grackles (Quiscalus major), a passerine bird (“songbird”) that people commonly see and hear along the Georgia coast. Grackles belong to to an evolutionarily related group (clade) called Icteridae, colloquially known as “blackbirds.” I frequently see grackle tracks on the upper parts of beaches and in the dunes, where they are oftentimes the most common vertebrate traces above the high tide mark on Georgia shorelines.
What was strikingly atypical this time, though, was how all of the grackles I saw making tracks were adult females. Female grackles are distinguished from males by their brown coloration, whereas the males are iridescent black, almost deep purple when viewed in the right light. Female adult grackles are also noticeably smaller than adult males, at about 70% their lengths and half their weights. Like most passerine birds, grackles have four-toed anisodactyl feet, with the “thumb” (digit I) pointing directly backwards with respect to its three forward-pointing toes (digits II-IV). Such tracks show their feet are well adapted for grasping branches in trees; yet they hang out along shorelines and nest near water bodies. I also wondered whether the tracks of this gender-sorted assemblage could be distinguished from those of the larger males, but didn’t get a chance to test this idea.
Girlfriends going out for a bite to eat by the beach: a group of boat-tailed grackles – all female adults – foraging in between the sea oats on the south end of Tybee Island. Here they were on the seaward side of the dunes, and just before sundown. (Photograph by Anthony Martin.)
Yet it wasn’t track sizes that caught my attention: it was what they were doing and the traces they were leaving. They were actively foraging, walking in between stalks of the sparsely populated sea oats (Uniola paniculata), which were barely holding down the dunes. This meant lots of slow, methodical walking with their heads down, and beaks actively snatching anything of interest. What were they finding and eating? On an over-developed island like Tybee, it could be almost anything. Grackles are notoriously omnivorous, which explains why they’ve easily adapted and thrived along the eastern coast of the U.S. despite extensive human alterations to this island and elsewhere.
Grackles in different feeding postures: two with their heads down and feet together (foreground and right), and another with her head up and left leg ahead of her right, and all after walking slowly and stopping often. With that in mind, think of the trackway patterns that would correspond with these movements and postures. (Photograph by Anthony Martin, taken on Tybee Island.)
So here’s what’s cool: these grackles were eating locally by chowing down on sea oats. That’s right, given all of the human-provided junk food they had available, they were going for the all-natural, organic, raw, and totally vegetarian option. (Tragically, it was not gluten free. But I think they were OK with that.) As a result, their tracks showed lots of short steps (diagonal walking) punctuated by “T-stops,” where they stopped to place their feet side-by side (making a “T” pattern), all of which were accented by beak traces, the last of these intersecting depressions formerly occupied by the sea-oat grains.
A close-up of the grackle from the previous photo, showing exactly why it stopped it with its feet together and put its beak down to the sand: fallen grains of sea oats. (Photograph by Anthony Martin, taken on Tybee Island.)
Another close-up of a grackle, but with sea oats in her beak. More importantly, check out the tracks behind her, the little depression where the oats laid on the sand (arrow), and the beak mark next to it that she made just before grabbing the grains. (Photograph by Anthony Martin, taken on Tybee Island.)
Boat-tailed grackle tracks that say, “I’m out looking for food, and whole grains only, please.” Note the “T-stop” pattern in the tracks and a beak impression within the trackway (center bottom) coinciding with some sea-oat grains, and a similar set of traces toward further down the trackway. (Photograph by Anthony Martin, taken on Tybee Island.)
So if you’ve read anything written by me before now, you probably know what I’m going to do next. (No, not that. But maybe next time.) I’m probably going to say, “Hey y’all, why don’t you look for traces like these next time you’re out walking along the beach?” But I’m also likely to say, “Gee, I wonder if traces like these would show up in the fossil record?” Both are important questions to keep in mind, even though the first deals with the here and now, whereas the other dives into deep time.
As a paleontologist, though, I’m all about the deep-time question. For example, when did the ancestors of grackles and other blackbirds start eating seeds from the ancestors of the sea oats, and in coastal environments? How would we know when these proto-grackles started having cereal for breakfast? If any trace fossils that look like the ones shown here do somehow got preserved, they should help connect those dots between all of the genes, bones, and other scientific evidence we use to figure out the evolution of this diverse clade of blackbirds.
Yeah, I know, it’s a body fossil. But hey, it’s the Berlin specimen of Archaeopteryx, probably the most famous body fossil in the world, so it’s OK. I was lucky enough to see it in person at the Museum für Naturkunde in Berlin early last month, and like most paleontologists who see it, I was awestruck by its 150-million-year-old beauty. Understandably, then, the evolutionary history of birds was on my mind when – three weeks later – I watched those grackles making traces on a Georgia beach. Will Archaeopteryx trace fossils ever be found? Let’s hope so, and if they do, they deserve to be as famous as this specimen. (Photograph by Anthony Martin.)
Plan to be surprised. That’s my adopted attitude whenever I’m on a developed barrier island of the southeastern U.S. coast and looking for animal traces. When primed by such open-mindedness, I’ve found that looking beyond the expected – or listening for the whispers below the shouts – can sometimes yield traces of the unexpected.
A beach-to-dune-to-fencing-to-vacation-home transect on the south end of Tybee Island, Georgia. Not much for an ichnologist or any other naturalists to learn here, right? Try, try again. (Photograph by Anthony Martin.)
Last month, just a couple of days after a successful book-related event in Savannah, Georgia (described here), my proximity to the Georgia coast meant I had to get to the nearest barrier island, which was Tybee Island. However, a challenge presented by Tybee – and the one that causes most coastal naturalists to run away from it screaming – is its degree of development.
Actual footage of a cephalopod ichnologist reacting to the news that a field trip would go to a developed barrier island. P.S. Octopus tentacle prints would make for the coolest trace fossils ever. (Source here.)
Accordingly, Tybee Island also has large numbers of people, especially on a pretty weekend during the summer. Granted, the development is not so awful that Tybee no longer has beaches and marshes. But it does have enough paved streets, houses, vacation rentals, hotels, restaurants, shops, and other urban amenities that you can easily forget you’re on a barrier island.
An oddly shaped beach on the south end of Tybee Island, molded by a combination of a seawall, big blocks of igneous rock, fences, boat wakes, and oh yeah, waves, tides, and sand. Better than a shopping mall, for sure, but it takes some getting used to for naturalists who do their field work in less peopled places. (Photograph by Anthony Martin.)
Tybee’s beaches are also “armored” with rip-rap and seawalls, which were placed there in a vain attempt to keep sand from moving. (On a barrier island, this is like telling blood it can only circulate to one part of a body.) Moreover, its modest coastal dunes rely on fencing as a half-buttocked substitute for healthy, well-rooted vegetation holding the sand in place. The sand in those dunes also looks displaced to anyone acquainted with Georgia-coast dunes on undeveloped islands. This is because that sand really is from somewhere else, having been trucked in from somewhere else and dumped there for beach “renourishment.” There’s also not much of a maritime forest there, or freshwater ponds. So yeah, I guess those cranky naturalists have a point.
Another view of the south end, showing the sharp vertical drop between the beach and dunes because of the seawall between them. The rocks (foreground) probably didn’t help much, either. (Photograph by Anthony Martin.)
Ergo, a pessimistic expectation I had before arriving on Tybee is that it would have a barrage of human and dog tracks, a tedium only punctuated by human-generated trash, all of which would assault and otherwise insult my ichnological senses. Fair or not, this prejudice kept me away from Tybee when I was doing field research for Life Traces of the Georgia Coast, and I stayed off St. Simons Island for a while, too, before succumbing in 2009. (I’m glad my wife Ruth convinced me to visit St. Simons – and I’ve been back several times since – but the interesting ichnology of St. Simons is the topic of another post.)
But then again, there was the matter of honoring the all-American right to convenience. Tybee Island is only about a 20-minute drive from Savannah, and you could drive there thanks to a causeway that connects the island to the mainland. Plus I had been to Tybee several times with students on field trips, and knew that lots could be learned there if I put a gag on my cynicism. I even had a research question, wondering how many ghost crab burrows would be in the dunes there compared to other Georgia barrier islands.
So thanks to the Hartzell Power Couple™, who were hosting Ruth and me in Savannah for the aforementioned book event, we were in their car on a Saturday morning and soon found ourselves walking on the south end of the Tybee, checking out its dunes and beaches, and (of course) their traces.
Fortunately, my question about the ghost crab burrows was answered within a few minutes of arriving at the south-end beach. Sure enough, we spotted a few of these distinctive holes, sand piles outside of the holes, and ghost-crab tracks scribbled on the dunes. Their traces weren’t nearly as common as on other undeveloped islands, but still, there they were.
Ghost crab burrows really do exist on developed barrier islands: whoa! Although it’s still a good question about their relative abundance on a developed Georgia barrier island versus one that’s barely altered, like nearby Wassaw Island. Sounds like some science needs to be done on that. (Photograph by Anthony Martin.)
But here’s the coolest thing we saw, ichnologically speaking. The dunes also had little holes that were about the width of a pencil, with crescent-shaped openings and fresh sand aprons just outside these holes.
What have we here? A little hole in the dunes with some freshly dumped sand outside of it. The game’s afoot! (Photograph by Anthony Martin.)
A close-up look of another hole very similar to the previous one. I wonder what could have made this? Oh well, I guess we’ll never know. Unless you read more, that is. (Photograph by Anthony Martin.)
I was pretty sure what made these, but as a scientist, I needed more evidence. So after pointing out the holes to my companions (Ruth and the Hartzell Power Couple™), we stood in one place and waited a few minutes. That’s when one of the tracemakers arrived.
Behold, the mystery tracemaker revealed! Check out that incredible digging! She’s got legs, and knows how to use them! (Photograph by Anthony Martin.)
Hypothesis confirmed! I predicted these were wasp burrows, and after watching several flying around the dunes, landing, walking up to and entering the holes, digging energetically, and emerging (repeat cycle), this was all of the evidence I needed. The wasps were some species of Stictia (sometimes nicknamed “horse-guard wasps” because they prey on horse flies). Moreover, these were female wasps making brooding chambers, little nurseries where they were going to lovingly lay eggs on paralyzed prey as a form of parasitoid behavior. (P.S. I absolutely adore parasitoid wasps, and you should, too.)
Up-close view of the same wasp burrow shown above. Oh, she’s in there, all right. See those sand grains getting kicked out of the burrow? (Photograph by Anthony Martin, taken on Tybee Island.)
In our too-brief time there on Tybee, we also saw feral cat tracks in the dunes. This is a common trace on developed islands, especially where people live year-round. Sometimes these are from pets that residents let roam free, but more likely these are made by the descendants of escaped cats that then breed in the wild.
Feral cat cats on dune sands, probably a day old at the time the photo was taken, eroded by wind and rain (see the raindrop impressions?). How to tell cat tracks from little foo-foo dog tracks? Cats make round compression shapes, a three-lobed heel pad, and rarely show claws. (Photograph by Anthony Martin, taken on Tybee Island.)
Another possible trace from a feral cat was an opened bird egg we found on the dunes. Admittedly, I’m quite the ichnological novice when it comes to egg traces, and can’t tell for sure whether this one was from predation (by a cat or other egg predator) or from hatching. But some clues are there, such as nearly half of the eggshell fragments adhering to the inside of the shell, instead of being absent.
Is it a birth trace or a death trace? Empty bird eggshells always present such questions. (Photograph by Anthony Martin, taken on Tybee Island.)
Down on the beach, one of the most common (and hence easiest) traces to find on Tybee or any other developed island with clam or snail shells washing up on their shores are predatory drillholes made by moon snails, the lions of the tidal flat. Sometimes these shells also have smaller holes, which are made by clionid sponges. Shells can thus bear the histories of life-and-death and life-after-death.
These shells are looking a little bored. (Yes, that’s a pun, albeit not a very good one.) The clam shell on the left was bored by a clionid sponge, and the three shells on the right were made by moon snails, probably Neverita duplicata. (Photograph by Anthony Martin, taken on Tybee Island.)
Once we were off the beach and walking on a paved road to where the car was parked, the ichnology didn’t stop then, either. In front of the car was a tree with some beautifully expressed rows of yellow-bellied sapsucker drillholes in its trunk.
What can I say, I’m a sucker for sapsucker holes. (Photograph by Anthony Martin, taken on Tybee Island.)
So can you still do ichnology on Tybee Island, or other developed barrier islands, for that matter? Looks like…
So next time you go on that beach vacation to Tybee, Jekyll, St. Simons, or other developed barrier islands, may you likewise be pleasantly surprised on your ichnological endeavors. Good luck!
Among my favorite tracemakers of the Georgia barrier islands are birds, a fondness inspired by their great variety (more than 200 species), numbers, and diverse behaviors. But if pressed to name my absolute favorite types of bird traces, I would not hesitate to say “flying tracks.”
Tracks from a great egret (Ardea alba) on a hard-packed beach sand that say, “I just flew in, and boy are my arms tired.” Notice the offset right-left tracks, long scratch marks left by claws on the rear toes, and cohesive bits of sand pushed forward by the egret’s feet when they contacted the sand. (Photograph by Anthony Martin, taken on Jekyll Island, Georgia.)
Now, “flying tracks” may sound contradictory, as a bird in flight leaves no tracks. But for those birds for which flight is an everyday habit, they take off and land, and many of these birds do so on the ground. This fact of avian life is recorded faithfully in the sands and muds of the Georgia barrier islands, and I have often delighted in encountering such tracks made by birds from sparrows to grackles to seagulls to pelicans to great blue herons. When covering this topic in my book (Life Traces of the Georgia Coast, just in case you needed reminding), I had to restrain myself from writing too much about it. Fortunately for readers, though, I described flight traces in enough detail there that I’m confident most people will be able to spot and recognize them. The following pictorial guide, most of which I showed during a recent talk to the Atlanta Audubon Society, should also help.
Flight tracks of a small songbird (probably a species of sparrow) on coastal-dune sands, showing that it didn’t stick around very long: landing, a hop, then take-off. (Photograph by Anthony Martin, taken on Little St. Simons Island, Georgia.)
How to tell whether a bird was landing or taking off? Your first clue should be a blank area in mud or sand, which will be devoid of tracks just behind a bird trackway, or the opposite, a trackless place just beyond the last footprints. In both instances, tracks are normally paired (side-by-side). For example, here’s an entire sequence made by a common ground dove (Columbina passerina), from landing to walking to take-off.
Entire landing, walking, and take-off sequence for a common ground dove (Columbina passerina) in back-dune area. Notice how it avoided the ghost-crab burrow by walking around it just before deciding to exit the scene. (Photograph by Anthony Martin, taken on Sapelo Island, Georgia.)
Close-up of landing tracks, in which this ground dove came in from the right, then shuffled its feet to shift direction to its right. (Photograph by Anthony Martin.)
Close-up of take-off tracks, where this ground dove was walking normally, then put its feet together and did one of its typically instant take-offs. (Pro-ichnologist tip: the scratch marks to the right are ghost crab tracks, not wing impressions.) (Photograph by Anthony Martin.)
Look closer at potential flight tracks and you will see other details that tell you whether a bird was coming down to earth or bidding the ground goodbye. Landing tracks often have long impressions behind them, “skid marks” that show how the bird decelerated and controlled its fall through a combination of body positioning and calculated flapping.
For larger birds with a backwards-pointing toe (hallux) – such as herons or egrets – these tracks usually leave a lengthy scratch mark from the claw on that foot. While landing, one foot plants in front of the other – either as an offset right-left or left-right pair – and the first track normally has the longer scratch mark. Either footprint also may have some mounding of mud or sand in front of it, as the forward momentum of the bird exerted pressure against whatever medium it encountered.
Another look at those great egret landing tracks shown previously, but now probably understood a little better through the power of words combined with images. ¡Viva Comunicación de la Ciencia! (Photograph by Anthony Martin.)
Close-up of that great egret’s right track, with features showing how its foot slid across the beach surface as it slowed its descent, then stopped. (Photograph by Anthony Martin.)
In the following video of a sparrow both landing and taking off, watch how it points its rear claws toward the surface as it approaches, then make first contact, followed by the forward-pointing toes. Also notice how one foot barely precedes the other, which in its tracks would should up as a very slight offset between the two. (Warning: This video is exquisitely beautiful, and is best watched with mouth agape in wonder.)
Depending on how fast a bird came down, and taking into account lots of other factors (for example, wind direction and speed), this landing pattern could be followed by a hop, or it could just segue into a normal diagonal walking pattern. Also keep in mind that birds with small or absent halluces (plural of hallux) and full webbing between their toes – such as gulls – may just show their forward three digits skidded, leaving no claw marks in the rear part of the tracks.
Landing tracks of a laughing gull (Leucophaeus atricilla), in which it first skidded, but must have had enough forward momentum to keep it going forward with a big hop. (Photograph by Anthony Martin, taken on Sapelo Island, Georgia.)
Close-up of a different set of landing tracks from a laughing gull with nicely defined skid marks on both feet. (Photograph by Anthony Martin, taken on Sapelo Island, Georgia.)
Take-off patterns involve opposite movements, in which the feet come together, but the digits dig in and push off, leaving scratch marks from the claws and well-defined mounds of sand or mud behind the digits, instead of in front of them. They can also be quite ungainly: I’ve seen pelican and vulture trackways in which they either run or skip for five-six steps before they were aloft, with increasing distances between each successive set of tracks. But sometimes a large bird like a pelican can impress me with its tracks, showing where it successfully accomplished a sudden take-off from a standing start.
Take-off tracks of a brown pelican (Pelecanus occidentalis) in which it must have flown from a standing start. Also note the water-drop impressions in front of the tracks, indicating that the pelican had just been in the water and still had wet feathers when it took off. (Photograph by Anthony Martin, taken on Sapelo Island, Georgia.)
So given these search images, lots of birds, and blank canvases of coastal sand or mud, you should now be able to find and diagnose your own “flying tracks.” But you also don’t need to restrict your searches to beaches: these traces can be found wherever flying birds live and visit the ground.
Using such clues, could we ever apply them to recognize flying tracks from the fossil record? Why, yes indeed. And for those of you who read this fair, here’s your Easter egg. The contents of this post relate to a major scientific discovery that will be announced in a few days: you heard it here first. So look for that news to come in for a landing soon.
Life can certainly imitate art, as can life traces. I was reminded of this last week while doing field work on St. Catherines Island (Georgia), and after encountering traces made by two very different animals, alligators and fiddler crabs. What was unexpected about these traces, though, was how they intersected one another in a way that, for me, evoked scenes from the recent blockbuster summer movie, Pacific Rim.
Could these be the tracks of a kaiju, making landfall on the shores of Georgia? Sorry to disappoint you, but they’re just the right-side and very large tracks of an American alligator (Alligator mississippiensis), accompanied by its tail drag-mark, left on a sandy area next to a salt marsh. Note the scale impressions in its rear-foot track, a symbol of the awesome reptilian awesomeness of its tracemaker. But wait: what nefarious nonsense is happening to the tail drag-mark, which is being covered by tiny balls of sand? Who made that hole next to the drag-mark? And what the heck was a raccoon (Procyon lotor) doing in the neighborhood, leaving its track on the tail drag-mark? With such a monster on the loose, shouldn’t that raccoon be hiding in the forest? (Photo by Anthony Martin, taken on St. Catherines Island; scale in centimeters.)
For anyone who has not seen Pacific Rim, you can read what I wrote about its distinctive fictional ichnology here. But what came to my mind while I was doing field work was one of the themes expressed early on in the film: how quickly humanity returned to normalcy following a lull in attacks by gigantic monsters (kaiju) that emerged from the ocean, destroyed major cities, and killed millions of people. It reminded me of how horrific hurricanes can strike a coast, such as the 1893 Sea Islands Hurricane that hit Georgia, but because no hurricane like it has happened there since, coastal developers think it’s hunky-dory to start building on salt marshes.
But enough about malevolent evil as exemplified by kaiju and coastal developers: let’s get back to traces. Last week, I was on St. Catherines Island for a few days with my wife (Ruth) and an undergraduate student (Meredith) to do some field reconnaissance of my student’s proposed study area. The area was covered by storm-washover fans; these are wide, flat, lobe-shaped sandy deposits made by storm waves, which span from the shoreline to more inland on barrier islands. We were trying to find out what traces had been left on these fans – tracks, burrows, scrapings, feces, and so on – which would tell us more about the distribution and behaviors of animals living in and around the washover fans.
Part of a storm washover fan on St. Catherines Island (Georgia), with the sea to the left and salt marsh (with a patch of forest) in the background. Say, I wonder what made those tracks coming out of the tidal creek and toward the viewer? (Photograph by Anthony Martin.)
It didn’t take long for us to get surprised. Within our first half hour of walking on a washover fan and looking at its traces, we found a trackway left by a huge alligator, split in half by a wavy tail-drag mark. I recognized this alligator from its tracks, as I had seen them in almost exactly the same place more than a year before. Besides their size, though, what was remarkable about these tracks was their closeness to a salt marsh behind the washover fan. When we looked closer, we could see long-established trails cutting through the salt-marsh vegetation, which were the width of a large adult alligator.
That ain’t no skink: the distinctive tracks and tail drag-mark of a large alligator, strolling through a storm-washover fan and next to a salt marsh. You think these animals are “freshwater only”? Traces disagree. Scale = 10 cm (4 in). (Photograph by Anthony Martin, taken on St. Catherines Island, Georgia.)
Alligator trail cutting through a salt marsh. Trail width was about 45-50 cm (18-20 in), which is about twice as wide as a raccoon trail. And it wasn’t made by deer or feral hogs either, because, you know, alligators. (Photograph by Anthony Martin, taken on St. Catherines Island, Georgia.)
So although the conventional wisdom about alligators is that these are “freshwater-only” animals, their traces keep contradicting this assumption. Sure enough, in the next few days, we saw more alligator tracks of varying sizes going into and out of tidal creeks, salt marshes, and beaches.
Based on a few traits of these big tracks, such as their crisp outlines (including scale impressions), the alligator had probably walked through this place just after the tide had dropped, only a couple of hours before we got there. But when we looked closer at some of the tracks along the trackway, we were astonished to see that something other than the tides had started to erase them, causing these big footprints to get fuzzy and almost unrecognizable.
The culprits were sand fiddler crabs (Uca pugilator), which are exceedingly abundant at the edge of the storm-washover fans closest to the salt marshes. These crabs are industrious burrowers, making J-shaped burrows with circular outlines corresponding to their body widths. They also scrape the sandy surfaces outside of their burrows to eat algae in the sand, then roll up that sand into little balls, which they deposit on the surface.
In this instance, after this massive alligator had stomped through their neighborhood, they immediately got back to work: digging burrows, scraping the surface, and making sand balls. Within just a few hours, parts of the alligator trackway was obscured. If these parts had been seen in isolation, not connected to the clear tracks and tail drag mark, I doubt we would have identified these slight depressions as large archosaur tracks.
Hey, what’s going on here? Who would dare to erase and fill in giant alligator tracks? Don’t they know who they’re dealing with? (Photograph by Anthony Martin, taken on St. Catherines Island, Georgia.)
Going, going, gone: alligator tracks nearly obliterated by burrowing, surface scraping, and sand balls caused by feeding of sand fiddler crabs (Uca pugilator). (Photograph by Anthony Martin, taken on St. Catherines Island, Georgia; scale in centimeters.)
What was even neater, though, was how some of the fiddler crabs took advantage of homes newly created by this alligator. In at least a few tracks, we could see where fiddler crabs had taken over the holes caused by alligator claw marks. In other words, fiddler crabs saw these, said, “Hey, free hole!”, and moved in, not caring what made them.
Don’t believe me about fiddler crabs moving into alligator claw marks? OK, then what’s that I see poking out of that alligator claw mark (red square)? (Photograph by Anthony Martin, taken on St. Catherines Island, Georgia; scale in centimeters.)
Why, it’s a small sand fiddler crab! Does it care that its new home is an alligator claw mark? Nope. Does ichnology rule? Yup. (Photograph by Anthony Martin, taken on St. Catherines Island, Georgia.)
Need a free burrow? Then why start digging a new one when alligator claw marks (arrow) gives you a nice “starter burrow”? Notice the sculpted, round outline, showing the claw mark was modified by a crab. Also check out the sand balls left outside of the other claw marks, meaning these have probably been occupied and mined for food by fiddler crabs, too. (Photograph by Anthony Martin, taken on St. Catherines Island, Georgia; scale in centimeters.)
As a paleontologist, the main lesson learned from this modern example that can be applied to fossil tracks, is this: any tracks made in the same places as small, burrowing invertebrates – especially in intertidal areas – might have been destroyed or otherwise modified immediately by the burrowing and feeding activities of those much smaller animals. The secondary lesson is on how large vertebrate tracks can influence the behaviors of smaller invertebrates, resulting in their traces interacting and blending with one another.
More symbolically, though, these alligator tracks and their erasure by fiddler crabs also conjured thoughts of fictional and real analogues: Pacific Rim and coastal development, respectively. With regard to the latter, it felt too much like how, as soon as a hurricane (a meteorological “monster”) passes through a coastal area, we begin to talk about rebuilding in a way that, on the surface, wipes out all evidence that a hurricane ever happened.
Yet unlike fiddler crabs, we have memories, we have records – including the plotted “tracks” of hurricanes – and thanks to science, we can predict the arrival of future “monsters.” So the preceding little ichnological story also felt like a cautionary tale: pay attention to the tracks while they are still fresh, and be wary of those that vanish too quickly.
Given the truth that the Atlantic horseshoe crab (Limulus polyphemus)is more awesome than any mythical animal on the Georgia coast (with the possible exception of Altmaha-ha, or “Altie”), it’s no wonder that other animals try to steal its power by eating it, its eggs, or its offspring. For instance, horseshoe-crab (limulid) eggs and hatchlings provide so much sustenance for some species of shorebirds – such as red knots (Calidris canutus) and ruddy turnstones (Arenaria interpres) – that they have timed their migration routes to coincide with spawning season.
Something hunted down, flipped over, and ate this female horseshoe crab while it was still alive. Who did this, what clues did the killer leave, and how would we interpret a similar scenario from the fossil record? Gee, if only we knew some really cool science that involved the study of traces, such as, like, I don’t know, ichnology. (Photograph by Gale Bishop, taken on St. Catherines Island, Georgia, on May 4, 2013.)
Do land-dwelling birds mammals eat adult horseshoe crabs? Yes, and I’ve seen lots of evidence for this on Georgia beaches, but from only three species: feral hogs (Sus crofa) and vultures (Coragyps atratus and Cathartes aura: black vultures and turkey vultures, respectively). In all of these interactions, no horseshoe-crab tracks were next to their bodies, implying they were already dead when consumed; their bodies were probably moved by tides and waves after death, and later deposited on the beach. This supposition is backed up by vulture tracks. I’ve often seen their landing patterns near the horseshoe-crab bodies, which means they probably sniffed the stench of death while flying overhead, and came down to have an al fresco lunch on the beach.
Nonetheless, what I just described is ichnological evidence of scavenging, not predation. So I was shocked last month when Gale Bishop, while he was monitoring for sea-turtle nests on St. Catherines Island (Georgia), witnessed and thoroughly documented an incident in which a raccoon (Procyon lotor) successfully preyed on a live horseshoe crab. Yes, that’s right: that cute little bandit of the maritime forest, going down to a beach, and totally buying into some Paleozoic diet plan, a passing fad that requires eating animals with lineages extending into the Paleozoic Era.
So what’s the big deal here? Horseshoe crab comes up on beach, gets lost, spirals around while looking for the ocean, and dies in vain, a victim of its own ocean-finding ineptitude: the end. Nope, wrong ending. For one thing, those horseshoe crab tracks are really fresh, meaning their maker was still very much alive, then next thing it knows, its on its back. Seeing that horseshoe crabs are not well equipped to do back-flips or break dance, I wonder how that happened? (Photograph by Gale Bishop, taken on St. Catherines Island, Georgia, and you can see the date and time for yourself.)
Here is part of the field description Gale recorded, which he graciously shared with me (and now you):
“Female Horseshoe Crab at 31.63324; 81.13244 [latitude-longitude] observed Raccoon feeding on upside-down HSC [horseshoe crab] on south margin of McQueen Inlet NO pig tracks. Relatively fresh HSC track. Did this raccoon flip this HSC?”
Well, well. Looks like we had a little commotion here. Lots of marks made from this horseshoe crab getting pushed against the beach sand, and by something other than itself. And that “something else” left two calling cards: a urination mark (left, middle) and just above that, two tracks. I can tell you the tracks are from a raccoon, and Gale swears the urination mark is not his. (Photograph by Gale Bishop, taken on St. Catherines Island, Georgia, and on May 4, 2013.)
I first saw these photos posted on a Facebook page maintained by Gale Bishop, the St. Catherines Island Sea Turtle Program (you can join it here). This was one of this comments Gale wrote to go with a photo:
GB: “This HSC must have been flipped by the Raccoon; that was NOT observed but the fresh crawlway indicates the HSC was crawling across the beach and then was flipped – only tracks are Rocky’s!”
[Editor’s note: “Rocky” is the nickname Gale gives to all raccoons, usually applied affectionately just before he prevents them from raiding a sea-turtle nest. And by prevent, I mean permanently.]
My reply to this:
AM: “VERY fresh tracks by the HSC, meaning this was predation by the raccoon, not scavenging.”
In our subsequent discussions on Facebook, Gale agreed with this assessment, said this was the first time he had ever seen a raccoon prey on a horseshoe crab, and I told him that it was the same for me. This was a big deal for us. He’s done more “sand time” on St. Catherines Island beaches than anyone I know (every summer for more than 20 years), and in all my wanderings of the Georgia barrier island beaches, I’ve never come across traces showing any such behavior.
(Yes, that’s right, I know you’re all in shock now, and it’s not that this was our first observance of this phenomenon. Instead, it is that we used Facebook for exchanging scientific information, hypotheses, and testing of those hypotheses. In other words it is not just used for political rants, pictures of cats and food, or political rants about photos of cat food. Which are very likely posted by cats.)
Now, here’s where ichnology is a pretty damned cool science. Gale was on the scene and actually saw the raccoon eating the horseshoe crab. He said it then ran away once it spotted him. (“Uh oh, there’s that upright biped with his boom stick who’s been taking out all of my cousins. Later, dudes!”) And even though I trust him completely as a keen observer, excellent scientist, and a very good ichnologist, I didn’t have to take his word for it. His photos of the traces on that Georgia beach laid out all of the evidence for what he saw, and even what happened before he got there and so rudely interrupted “Rocky” from noshing on horseshoe-crab eggs and innards.
Another view of the “death spiral” by the horseshoe crab, which we now know was actually a “life spiral” until a raccoon showed up and updated that status. Where’s the evidence of the raccoon? Look in the middle of the photos for whitish marks, grouped in fours, separated by gaps, and each forming a backwards “C” pattern. Those are raccoon tracks, and it was galloping away from the scene of the crime (toward the viewer).
So you don’t believe me, and need a close-up of that raccoon gallop pattern? Here you go. Both rear feet are left, both front feet are right, and the direction of movement was to the left; when both rear feet exceed the front, that’s a gallop, folks. Notice the straddle (width of the trackway) is a lot narrower than a typical raccoon trackway, which is what happens when it picks up speed. When it’s waddling more like a little bear, its trackway is a lot wider than this. Conclusion: this raccoon was running for its life.
Although this is the only time Gale has documented a raccoon preying on a horseshoe crab – and it is the first time I’ve ever heard of it – we of course now wonder whether this was an exception, or if it is more common that we previously supposed. The horseshoe crab was a gravid female, and was likely on the beach to lay its eggs. Did the raccoon somehow know this, and sought out this limulid so that – like many shorebirds – it could feast on the eggs, too, along with some of the horseshoe crab itself? Or was it opportunistic, in that it was out looking for sea-turtle eggs, saw the horseshoe crab, and thought it’d try something a little different? In other words, had it learned this from experience, or was it a one-time experiment?
All good questions, but when our data set is actually a datum set (n = 1), there’s not much more we can say about this now. But given this new knowledge, set of search patterns, and altered expectations, we’re more likely to see it again. Oh, and now that you know about this, so can you, gentle reader. Let us know if you see any similar story told on the sands of a Georgia beach.
You want one more reason why this was a very cool discovery? It shows how evolutionary lineages and habitats can collide. Horseshoe crabs are marine arthropods descended from a 450-million-year-old lineage, and likely have been coming up on beaches to spawn all through that time. In contrast, raccoons are relative newcomers, coming from a lineage of land-dwelling mammals (Procyonidae) that, at best, only goes back to Oligocene Epoch, about 25 million years ago. When did a horseshoe crab first go onto land and encounter a land-dwelling raccoon ancestor? Trace fossils might tell us someday, especially now that we know what to look for.
So once again, these life traces provided us with a little more novelty, adding another piece to the natural history of the Georgia coast. Moreover, a raccoon preying on a horseshoe crab was another reminder that even experienced people – like Gale, me, and others who have spent much time on the Georgia barrier islands – still have a lot more to learn. Be humble, keep eyes open, and let the traces teach you something new.
(Acknowledgement: Special thanks to Dr. Gale Bishop for again spotting something ichnologically weird on St. Catherines Island, documenting it, and sharing what he has seen during his many forays there.)
Given all of the controversy over a recent cable-TV program, in which its broadcasting channel decided mythical marine animals deserved more air-time than real ones, I thought it was important to highlight one extant animal that never fails to surprise me. This animal’s lineage is more ancient than dinosaurs, reptiles, or even amphibians, with its oldest fossils dating from about 450 million years ago. It is also the largest living marine invertebrate animal you are likely to see on beaches of the eastern U.S. and Gulf Coast. And at this time of year, if you see it crawling around on a beach, it’s because of sex. For the past month or so, this animal has been participating in massive orgies. Pictures of this gamete-laden frenzy somehow made it past prudish censors of Facebook and other social-media sites, titillating prurient invertebrate enthusiasts everywhere and filling them with cockle-warming glee.
Behold, a fine juvenile specimen of the Atlantic horseshoe crab (Limulus polyphemus)! Although it lives in the ocean, it can walk on land for hours, like some sort of reverse Aquaman, but totally cooler than him. And some day, if this one lives long enough, it will use those legs to walk on land again, but in pursuit of sex. Sounds to me like this animal deserves its own planet. (Photograph by Anthony Martin, taken on Sapelo Island, Georgia.)
As you already know from reading the title of this post, I’m talking about horseshoe crabs. More properly known as limulids by real marine biologists and paleontologists, these ultra-cool, über-hip, but totally retro critters are more closely related to spiders than they are to true crabs, but their common name is so, well, common, that scientists just sigh and begrudgingly go along with it for the sake of public communication.
Modern limulids are represented by four species, three of which are in Asia, but the grandest of them all is the Atlantic horseshoe crab, Limulus polyphemus. This species is at its largest here in Georgia, which may be a function of the Georgia Bight, an extensive offshore shelf that affords more food and habitat than other areas. How big? I’ve seen some as long as 70 cm (27 in) – tail included – and 40 cm (16 in) wide, big enough to scare both of our cats at home. They grow to these sizes after hatching as little limulids not much bigger than the period on this sentence, an astonishing increase in mass if they make it to adulthood (which most don’t).
The circuitous trail of a baby limulid, made on a sandflat at low tide. Its body width can be estimated by the width of the interior of the trail, and its body length was slightly more than that, meaning it was smaller than my fingernail. See that central groove? That’s from its tail, but if you want to impress your friends, call it a telson. (Photograph by Anthony Martin, taken on Sapelo Island, Georgia.)
Horseshoe crabs are so astounding that I could go on endlessly about all sorts of facts about them. Fortunately for you, gentle reader, other folks have written entire books about them and heaps of popular and scientific articles. (For starters, try going here.) So I don’t want to needlessly duplicate what others have done, and done well. Instead, I’ll focus on my main interest in these animals – their traces – and will regale you with tales of the traces they can make with their tails.
Horseshoe crab tails are spiky projections called telsons. Based on lots of the traces I’ve seen on the Georgia coast and a few direct observations, the main function of a telson is to help a horseshoe crab to get back on its feet after being knocked onto its back. That is, whenever a limulid is upside-down, it immediately start using its telson as a sort of sideways pole vault to lever itself into a less vulnerable position.
Without a telson, an upside-down horseshoe crab is stuck; its legs run furiously, but to no avail. However, with a telson, it can put the pointy end into the sand or mud underneath its body, and push itself up from a surface. This gives a limulid a fighting chance to get back to where it once belonged and start walking. This strategy works best if it turns to its right or left side, as limulids are longer than wide. They may be wonders of nature, but they’re not doing back flips or somersaults.
A large adult horseshoe crab that was right-side-up when trying to get back to the sea, got tired, and tried to use its telson to move itself along. In this instance, it didn’t work, but the traces made by the telson show its range of motion, working like a windshield wiper. (Photograph by Anthony Martin, taken on Sapelo Island, Georgia.)
OK, all of the preceding information I already knew. After all, I have: coauthored an edited book chapter about juvenile limulid traces and their close resemblance to trace fossils made by trilobites; coauthored another article on the history of limulid-trace studies (which go back to the 1930s!) that’s now in review; and devoted a lengthy section of a chapter in my book to limulids as tracemakers. So you could say I’ve been feeling pretty cocky about what I knew about these animals as tracemakers. That is, until one horseshoe crab showed me how much I still need to learn about them and what they can make.
The humility-inspiring traces showed up in a photo on a Facebook page I follow (and so should you), the St. Catherines Island Sea Turtle Conservation Program. The program organizers – Gale Bishop and Robert (Kelly) Vance – regularly add photo albums showing sea turtle traces (trackways, body pits, nests), and otherwise report on other facets of natural history they observe on St. Catherines Island beaches. As a result, I live vicariously through these pictures while marooned in the metro-Atlanta area. But they also like to throw me ichnological stunners once in a while, such as the following photo that Kelly posted last week.
Who needs made-up animals on TV when traces like these, made by awesome invertebrates like horseshoe crabs, turn up on a Georgia beach? (Photograph by Robert Kelly Vance, taken on St. Catherines Island, Georgia; scale is about 15 cm (6 in) long.)
Kelly found these traces while patrolling the beaches of St. Catherines Island for other traces, namely those of expectant mother sea turtles. Although these distracted briefly from his mission, I was very happy he stopped to document these, as I had never seen anything like them, despite much looking at traces on Georgia beaches.
The holes in the sand, defining a nearly perfect circle, were made by the telson of an adult horseshoe crab that kept on trying to right itself after landing on its back. Each puncture mark shows where it inserted the telson into the sand and then pushed itself up and to its side. Based on the number of holes, direction of sand flung out of each hole, and little “commas” made by extraction of the telson, it tried to flip itself a minimum of 16 times, and all to the right. These separate actions culminated in a 360° clockwise rotation of its body. Also check out the central depression with smaller drag marks; this is where its head shield was in contact with the sand. To imagine the movement represented by these traces, think of a horseshoe crab doing a slow-motion, step-by-step, break-dance backspin.
Seeing the evidence for such persistence was wow-inducing in itself, but in my ichnologically influenced euphoria, I figured the limulid finally succeeded in righting itself. After all, the trackway just to the left of the trace, indicates where it walked away from the scene of its gravitationally challenged situation.
But then I realized there was no “impact mark.” This large horseshoe crab flipping itself onto the sandy surface should have registered an outline of its body before it started walking. Instead, the place where it started walking showed no such impression, meaning it must have made a soft landing, with only its legs and telson digging into the sand. What happened? Did it use mind over matter and levitate itself through telekinesis? Or was it gently picked up and placed on its feet by a merciful mermaid? (Or merman: let’s make sure we’re being inclusive when talking about made-up stuff.)
It turned out that Kelly was the dues ex machina that entered this limulid’s drama, providing divine intervention just when it was needed. When I expressed my puzzlement to Kelly about how this large arthropod finally turned itself over, he confessed to saving it, in which he lifted it and put it back on its feet, where it promptly walked away in a series of tight spirals. The spiraling is something I’ve seen before in their tracks, a method used to find the downslope direction, which normally leads horseshoe crabs to the low-tide mark and the comfort of a watery environment.
Another perspective of the “escape” traces made by the limulid’s telson (background), but this time with its tracks, showing how it started spiraling clockwise in an attempt to make its way back to the sea. Check out those telson drag marks in the trackway, doing a little bit of back-and-forth movement as its owner walked. (Photograph by Robert Kelly Vance, taken on St. Catherines Island, Georgia.)
OK everyone, start singing “Born Free!” The spiraling helped this limulid (arrow) to find a downslope direction, which took it in the right direction to the sea. But it’s not all sunshine and lollipops for other limulids, some of which are visible in the background, and look like they’re still stuck. Given the tidal range on the Georgia coast – 2.5-3 m (8.2-9.8 ft) – strong wave energy, and wide beaches, lots of big limulids that come in with the flood tide get knocked onto their backs by waves and left behind. It’s almost as if some sort of natural selection is taking place, and something similar might have happened in the geologic past, affecting the evolution of its lineage. (Photograph by Robert Kelly Vance, taken on St. Catherines Island, Georgia.)
In the last photograph, I was glad to see how the story told by these traces promised a happy ending for this limulid that had so stubbornly tried to put itself back on its feet. Yet when you also notice how many of its compatriots did not make it back into the life-nourishing sea, it also serves as a sobering reminder that storybook endings don’t always happen in nature, and what we wish to be true sometimes isn’t.
In this instance, I don’t know whether this horseshoe crab made it back into the sea to live another day or not. Still, the lesson it left for us in the sand lives on, and I am now slightly more confident that if any limulids were stuck on their backs at any point in their 450-million-year history, made similar traces with their tails, and these marks were preserved as trace fossils, we just might recognize them for what they are. For that alone, I am grateful. Thank you, horseshoe crabs, for being real, making traces, and continuing to share this planet with us today.
(Acknowledgement: Special thanks to Drs. Robert Kelly Vance and Gale Bishop for being my ichno-scouts on St. Catherines Island, and feeding my mind with such tasty treats while I am landlocked.)
Martin, A.J., and Rindsberg, A.K. 2007. Arthropod tracemakers of Nereites? Neoichnological observations of juvenile limulids and their paleoichnological applications. In Miller, W.M., III (editor), Trace Fossils: Concepts, Problems, Prospects, Elsevier, Amsterdam: 478-491.
Shuster, C.N., Jr., Barlow, P.B., and Brockmann, H.J. (editors). 2003. The American Horseshoe Crab. Harvard University Press, Cambridge, Massachusetts: 427 p.
All paleontologists remember their first time. Mine was in 1993, during a hot, steamy summer in Atlanta, Georgia. I had just spent the previous month camping in wilderness areas of Wyoming, so coming back to a big city with all of its urban temptations meant I was weak and susceptible to seeking out unusual sources of pleasure. Although I was not quite ready to be taken for such an exhilarating ride, it was an experience I’d never forget. Afterwards, once I had recovered enough to be able think about it, I wanted to do it again.
I am, of course, talking about seeing the film Jurassic Park on a movie screen. Sure, this movie has been around long enough (20 years) that nearly every paleontologist has also watched it on a TV, computer, or mobile device. But there is something about seeing dinosaurs – which, let’s face it, are most famous for their size – shown big. The initial glimpse of a Brachiosaurus munching on the tops of tall trees, a herd of Paralophosaurus ringing a glistening lake, an ill Triceratops dwarfing its human caretakers, the grand entrance of the Tyrannosaurus: all of these “actors” were meant to be seen large, and fill us with awe. It worked. Plot, acting, and science aside, Jurassic Park was, and probably still is, the best movie made for conveying what it would feel like for us humans, separated by a minimum of 65 million years, to see real, living dinosaurs.
“It’s, it’s a dinosaur.” That pretty much said it all in 1993, and still does. But what traces were being made by this Brachiosaurus as it strolled through its all-you-can-eat salad bar, known to you and me as a “landscape”? Please read on.
In 1993, though, I did not have an appreciation for some of the smaller details included in this film, and how my research specialty of ichnology – the study of traces, like tracks, burrows, and nests – was reflected throughout it. What dinosaur traces were included in the movie, and how were these traces used to serve or advance the plot? I also wondered how 20 years of field experience and scholarly research in ichnology might have changed my perceptions of it since that first viewing.
So with the re-release of Jurassic Park in 3-D last week, I decided it was time to view it from an ichnological perspective and share these thoughts with others. After all, my next book, Dinosaurs Without Bones (Pegasus Press), is about dinosaur trace fossils, and written for a popular audience. Also, in between the movie’s first release and now, I wrote two editions of a college textbook on dinosaurs (Introduction to the Study of Dinosaurs). Thus I went to the theater well justified in watching Jurassic Park once more, to see for myself how dinosaur traces were portrayed in the most well-loved of all dinosaur movies. And oh yes, for the fun.
For the sake of simplicity, I’ve divided these traces into two categories: those viewers could directly observe in the film, and others that could be inferred from the dinosaurs’ behaviors. Wherever possible, I also connect traces shown in the movie to research done on dinosaur trace fossils during the last 20 years, giving a broad sense of how far dinosaur ichnology has progressed since 1993.
(Ichnologist’s note: Even though all of the live dinosaurs in the movie were set in the 1990s, the study of their modern traces still qualifies as neoichnology. In contrast, any reference I make to actual dinosaur trace fossils is paleoichnology. Just so you know.)
Dinosaur Traces in Jurassic Park
• Velociraptor hatchling traces.Jurassic Park shows two different but complementary examples of hatchling traces for “Velociraptor.” (I will call this dinosaur Velociraptor throughout this post, but as most dino-philes know, the director, Steven Spielberg, scaled up the Late Cretaceous Velociraptor to maximize its frightfulness. Hence it is actually more like the Early Cretaceous Deinonychus or Utahraptor.)
One is an egg-emergence trace, which is the hole left in an eggshell where a dinosaur broke out of its egg. In this scene, a cooing Velociraptor hatchling pokes its cute little nose out of its egg. (This nose, if everything worked out for it, would some day would be warmed by fresh human viscera.) We first witness this tracemaking in the Jurassic Park laboratory toward the start of the film, the same day most of the protagonists arrive on the island (Isla Nublar). As far as I know, such trace fossils have not been interpreted from the fossil record, or if they have, they have not been referred to as trace fossils: which they should be.
The next day, after dinosaur paleontologist Alan Grant and his two companions – Lex and Tim Murphy – were sufficiently terrified (and enthralled) by various dinosaur encounters out in the park, they come across a Velociraptor nest. The nest has about 15-20 broken eggs, and the fracture patterns of the eggshells provide clear evidence of hatching. But these traces also had tiny, two-toed tracks leading away from them. The tracks, with two toes studded by digital pads, were typical for deinonychosaurs. However, unlike nearly every theropod track I’ve seen, these tracks lacked claw marks at their ends. (Tsk, tsk, says this nitpicking ichnologist.)
Aw, look at the cute little Velociraptor tracks and hatched eggs. Don’t these traces just make you want to say, “Who’s the cutest little predator in the world?” Still from Jurassic Park (1993), taken from www.anyclip.com.
Even though these tracks were flashed on the screen for only a few seconds, what’s really cool is how they convey three important pieces of information. One is that the Velociraptor chicks hatched after the torrential rainstorm of the previous night, and thus only mere hours before our wandering heroes saw their traces. Second, the tracks demonstrate that the hatchlings were not altricial, but ready to move and leave the nest immediately, presumably without parental care. Third, Dr. Grant realizes that these successfully fertilized and hatched eggs mean the “female-only” genetic fail-safe plan for the dinosaurs just got disproved. In other words, these traces mattered.
One point about that nest: as far as I could tell from, this Velociraptor mother did not make a rimmed structure to protect the eggs, such as those made by another Late Cretaceous theropod, Troodon, or LateCretaceous sauropods in Argentina. Instead, the eggs were laid out in the open, like some ground-nesting shorebirds might do. In contrast, the Jurassic Park sequels featured Velociraptor nests that were much more overt as traces, such as a rimmed nest seen in Jurassic Park III.
Partially preserved rimmed nest structure of Troodon, a Late Cretaceous theropod that lived in what we now call Montana. The rim has eroded quite a bit since its discovery in the mid-1990s; the Troodon egg clutch was in the area of the foreground before its extraction. (Photograph by Anthony Martin; scale in centimeters.)
• Triceratops feces. “That is one big pile of sh*t,” observes Dr. Ian Malcolm, the “chaotician” (mathematician) who supplies both pessimism and comic relief throughout the movie. In this scene, where the main protagonists attend to an under-the-weather Triceratops, two impressive piles of fecal material inspire Dr. Ellie Satler, a paleobotanist, to figure out whether or not the ceratopsian had eaten any toxic plants.
Somehow I suspect this scene was meant as a metaphor for what most paleontologists have to do in their day jobs in order to do any paleontology at all.
Still, when added together, this amount of still-moist waste was far too voluminous to have been from one or two depositional events: I mean, this dinosaur was sick, but not that much. As a result, park personnel must have been responsible for making these dung heaps from several days worthy of Triceratops contributions. (Strictly speaking, then, these heaps were composite traces.) If so, this would have been a rather unenviable job, but maybe they were better paid than Dennis Nedry, the disgruntled computer programmer who later provided ample fodder for Dilophosaurus.
Unfortunately, fossil Triceratops feces (coprolites) are thus far unknown from the geologic record. What is exciting, though, is that several excellent studies have been done by Dr. Karen Chin on Late Cretaceous hadrosaur coprolites. These coprolites, like the fictionalized Triceratops feces, contain lots of plant material, telling us much about what these hadrosaurs ate 75 million years ago. They also tell us what ate the feces or grazed on them, which were dung beetles and snails, respectively. (Indeed, I now wonder if Isla Nubar had a severe shortage of dung beetles, which might explain how those Triceratops feces got piled higher and deeper.)
Dinosaur coprolite – probably from a large hadrosaur, such as Maisaura – and filled with wood fragments, accompanied by special bonus trace fossils: dung beetle burrows! Specimen from the Two Medicine Formation (Late Cretaceous, Montana) as part of a Museum of the Rockies traveling exhibit at Fernbank Museum of Natural History. (Photograph by Anthony Martin, taken in 2001 and scanned from a 35-mm slide; scale in centimeters.)
• Tyrannosaurus tracks. Probably the most memorable scene in Jurassic Park is the grand entrance of the Tyrannosaurus, whose approach is first detected by “impact tremors” transmitted in cups of water on the dashboard of a jeep. Following this first bout of terror and the arrival of Ellie Sattler and big-game hunter Robert Muldoon, Malcolm, convalescing in the back of a jeep, looks down at a three-toed Tyrannosaurus track. The track, filled with water from the rain, communicates a warning as it vibrates from the footfalls of the approaching giant theropod. This repeats the previous image of the trembling water in the cup, but is made doubly dreadful by happening in a freshly made footprint of the same animal causing the tremors.
So what was by far the most exciting moment in the movie for me, ichnologically speaking? The Tyrannosaurus making a track, in which mud pushes up and out to the sides of its right foot, observed at 2:38 in the following video clip. Just watch:
This was already a great scene for all of its action, suspense, and lawyer eating. But check out that track-making!
Only a few fossil tracks have been attributed to Tyrannosaurus or other tyrannosaurids, mostly for being the right size (really big) and geologic age (Late Cretaceous). One was discovered in New Mexico in 1983, but wasn’t reported in a scientific journal until the year after Jurassic Park came out. More than a decade passed before another was found in Montana in 2007 and reported in 2008. Tragically, both were isolated tracks, and a Tyrannosaurus trackway, with two or more consecutive steps, has not yet been found. If so, it would make for a pretty darned nice find. So please do let the world know if you find one.
A large and well-preserved three-toed theropod track from the Early Cretaceous Glen Rose Formation of Texas, made about 95 million years ago. Although this track was more likely made by Acrocanthosaurus, rather than Tyrannosaurus rex, you can be assured that this theropod, like all living things, was a distant relative of T. rex. (Photograph taken by Anthony Martin; scale in centimeters.)
• Velociraptor tracks (adults). These tracks, shown only for a few seconds, are outside of the Velociraptor enclosure after the power was shut down. Muldoon, accompanied by Sattler, spots the footprints, and he wordlessly identifies them. (His expression also tells the audience that Sattler and he are going to be in deeper doo-doo than the Triceratops piles.) The twisted and broken bars of the enclosure provide additional traces affirming the conclusion that these ‘raptors are on the loose. All of these traces are shown only minutes before Muldoon utters his meme-inspiring last words, “Clever girl.”
Uh oh: Velociraptor tracks, and these don’t look like they’re from hatchlings. Good thing Muldoon is a big-game hunter, who’s skilled at tracking and predicting Velociraptor behavior based on their tracks. But too bad his hypothesis was falsified in such an unpleasant way, but I suppose he could have picked kinder reviewers. Still from Jurassic Park (1993), taken from www.anyclip.com.
Here’s what a real deinonychosaur track looks like. This one, from the Early Cretaceous of Utah, is a right foot impression, and is just slightly smaller than the adult tracks depicted in Jurassic Park. Notice the digits are thinner and end with sharp clawmarks, too. (Photograph by Anthony Martin; scale in centimeters.)
• Bioerosion of fossil dinosaur bones by modern dinosaurs. Toward the end of the film, the main human heroes – Grant, Sattler, Murphy, and Murphy (which sounds like a law firm, but we know how T. rex feels about those) – are confronted by a Velociraptor pack in the Jurassic Park visitor center. During their attempts to flee the ‘raptors, both species end up disarticulating and breaking some of the mounted dinosaur skeletons in the atrium of the visitor center. Their actions were thus a form of bioerosion, in which the fractured dinosaur bones are traces of their activities. Alternatively, the bones may have been artificial casts, in which case their breakage would have constituted bioerosion of modern substrates.
This bioerosion is made more complicated when the Tyrannosaurus rex (who everyone agrees is the ultimate protangonist of the movie) enters the atrium and, among other antics, smashes a skeleton of itself with a recently crunched Velociraptor. As a result, the jumbled assemblage of bones at the end is attributable to three separate, interacting tracemakers: four humans (two adult, two juvenile), two Velociraptors (both adults), and one Tyrannosaurus (adult). What should be noted, though, is that if the Velociraptor was already dead when flung by the Tyrannosaurus, then the broken skeleton is a trace of the Tyrannosaurus, not the Velociraptor. In other words, the Velociraptor body was just being used as a tool.
Bioerosion in action, as a result of Velociraptor and human interactions. Also, at 2:45: T. rex smash!
Dinosaur Trace-Making Behaviors in Jurassic Park
• Brachiosaurus tracks, browsing traces.When Drs. Grant and Sattler experience their first jaw-dropping glimpse of a Brachiosaurus, they watch it rear up on its hind feet, and come down hard on front feet. Considering that a Brachiosaurus this size might have weighed at least 30 tonnes, it surely would have left deep tracks in both the front and rear from the increased stresses imparted by these actions. Also, its cropping the tops of trees would have caused some easily visible gaps in the canopies of forests on Isla Nubar.
• Theropod toothmarks. Part of the fun of Jurassic Park was indulging in our worst nightmares about these non-avian theropods frequently sampling human flesh. Assuming that the theropod teeth in each instance penetrated skin and muscle and contacted bone, toothmarks would have included the following: (1) Tyrannosaurus toothmarks on goat, human, and Velociraptor bones; and (2) Velociraptor and Dilophosaurus toothmarks on human bones.
• Triceratops resting trace. When the paleontologists and others visit the ailing Triceratops, it was lying on its right side. I couldn’t help but think that if Triceratops or any other large ceratopsian dinosaur ever reclined like that, and in the right type of sediment, it would have left a gorgeous body impression. This scene also reminded me of bison traces I’ve seen in Yellowstone National Park, in which bisons roll onto their sides for a dust bath, leaving outlines of their bodies. Did dinosaurs – especially the feathered ones – ever take dust baths, and leave similar body impressions? We don’t know yet, but such trace fossils are something to look for.
• Dinosaur stampede. One of the most astonishing computer-generated effects of Jurassic Park, and one that was especially effective in 3-D, was of a dinosaur stampede. In this scene, a flock of Gallimus run toward and around Grant, Murphy, and Murphy, just before the ambush-hunting Tyrannosaurus rex slaughters one of them (the Gallimus, that is). I’ve written about this scene before, connecting it to a dinosaur tracksite in Queensland, Australia that has more than 3,000 tracks preserved. Although the site was originally interpreted as the only evidence of a dinosaur stampede, the tracks were recently reinterpreted as swim tracks. I’ll write about this topic at length in my upcoming book, so for now, I ain’t saying nothing more.
Run away, run away!
• Tyrannosaurus drag mark. After the Tyrannosaurus rex decides that a measly goat was just an appetizer and begins seeking out the nearest available mammals for nomming purposes, at some point it overturns and begins pushing an SUV, which still has Lex and Tim Murphy trapped underneath it. Its flipping the SUV with its head certainly would have left a substantial mark on the muddy ground, a trace that then would have been connected to a semi-circular dragmark (clockwise oriented), and with tracks directly adjacent to these traces. Her tracks also may have been deeper in their fronts because of her head being down as she pushed, reflecting a shift in her weight distribution. However, I should again remind everyone that just like with the dead Velociraptor used for bioerosion by this same T. rex later in the film, the SUV is not making the trace. It is only a tool being used by the tyrannosaur, which is the real tracemaker.
• Tyrannosaurus running trackway – This pulse-quickening chase scene, in which the T. rex pursues a jeep driven by Muldoon and with Malcolm and Sattler as passengers, very likely would have caused a wonderful sequence of tracks. These tracks would have shown increasing stride lengths from a standing start to full-speed run, and each successive track would have registered external and internal structures consistent with this acceleration. Even better, the tracks would have cross-cut the jeep tire-tracks at some points, demonstrating to a later observer that the tyrannosaur was very likely following the jeep. (The demolition of a low-hanging tree branch by the T. rex during the chase also counts as some bioerosion along the way.) Some convincing studies have been done since showing that an adult Tyrannosaurus could not have moved as fast as the one in Jurassic Park, but it still could have caught most running humans. And just to repeat what I said earlier, it’d be really nice for someone to find a T. rex trackway, which would give us more direct evidence of how these massive theropods moved.
• Velociraptor scratch marks and other traces. This time, while watching the harrowing and claustrophobic scene in which a pair of Velociraptors hunt the Murphy siblings in a kitchen, I started thinking about the traces they might have left. Did their claws leave scratch marks on the door handles and kitchen counters? Did they indent the steel counters when they jumped up on these surfaces? A broken window is also shown as a trace of their smashing through glass once they became frustrated with a locked door.
OK, enough of the fanciful ichnology. What about other dinosaurs and their traces? Well, it turns out that Jurassic Park saved the real, living dinosaurs for the very end of the movie. These were five brown pelicans (Pelecanus occidentalis), flying in formation as Grant, Sattler, and their companions leave Isla Nubar in a helicopter. For Grant, this is a poignant moment, as he is likely reflecting on how dinosaurs were still with us today as birds. With that thought, I will say “amen,” and add that dinosaur traces – tracks, nests, feces, bite marks, and all – are still here with us, too, and don’t require special glasses to see them in three dimensions. Thanks for that reminder, Jurassic Park.
Want to see some modern dinosaur traces? Here are tracks of a brown pelican, made in wet sand while it was loafing on a beach at low tide on Sapelo Island, Georgia. To see more modern dinosaur traces, just go outside, and you’ll find them wherever birds are found. (Photograph by Anthony Martin; scale in centimeters.)
Further Reading
Chiappe, L.M., Schmitt, J.G., Jackson, F., Dingus, L., and Grellet-Tinner, G. 2004. Nest structure for sauropods: sedimentary criteria for recognition of dinosaur nesting traces. Palaios, 19: 89–95.
Chin, K. 2007. The paleobiological implications of herbivorous dinosaur coprolites from the Upper Cretaceous Two Medicine Formation of Montana: why eat wood? Palaios, 22: 554-566.
Chin, K., and Gill, B.D. 1996. Dinosaurs, dung beetles, and conifers: participants in a Cretaceous food web. Palaios, 11: 280-285.
Elbroch, M., and Marks, E. 2001. Bird Tracks and Sign of North America. Stackpole Books, Mechanicsburg, Pennsylvania.
Erickson, G. M., Van Kirk, S. D., Su, J., Levenston, M. E., Caler, W. E., & Carter, D. R. 1996. Bite force estimation for Tyrannosaurus rex from tooth-marked bones. Nature, 382: 706–708.
Gignac, P.M., Makovicky, P.J., Erickson, G.M., and Walsh, R.P. 2010. A description of Deinonychus antirrhopus bite marks and estimates of bite force using tooth indentation simulations. Journal of Vertebrate Paleontology, 30: 1169-1177.
Hutchinson, J.R., and Garcia, M. 2002. Tyrannosaurus was not a fast runner. Nature,415: 1018-1021.
Jacobsen, A.R. 1998. Feeding behaviour of carnivorous dinosaurs as determined by tooth marks on dinosaur bones. Historical Biology, 13: 17-26.
Lockley, M.G., and Hunt, A.P. 1994. A track of the giant theropod dinosaur Tyrannosaurus from close to the Cretaceous/Tertiary Boundary, northern New Mexico. Ichnos, 3: 213-218.
Manning, P.L., Ott, C., and Falkingham, P.L. 2008. A probable tyrannosaurid track from the Hell Creek Formation (Upper Cretaceous), Montana, United States. Palaios, 23: 645-647.
Romilio, A., and Salisbury, S.W. 2011. A reassessment of large theropod dinosaur tracks from the mid-Cretaceous (late Albian–Cenomanian) Winton Formation of Lark Quarry, central-western Queensland, Australia: a case for mistaken identity. Cretaceous Research, 32: 135-142.
Romilio, A., Tucker, R., Salisbury, S. 2013. Reevaluation of the Lake Quarry dinosaur tracksite (late Albian-Cenomanian Winton Formation, central-western Queensland, Australia): no longer a stampede? Journal of Vertebrate Paleontology. 33: 1, 102-120.
Sellers, W.I., and Manning, P.L. (July 2007). Estimating dinosaur maximum running speeds using evolutionary robotics. Proceedings of the Royal Society of London, B, 274: 2711-2716.
Thulborn, R.A., and Wade, M., 1979. Dinosaur stampede in the Cretaceous of Queensland. Lethaia, 12: 275-279.
Varricchio, D.J., Jackson, F. and Trueman, C.N. 1999. A nesting trace with eggs for the Cretaceous theropod dinosaur Troodon formosus. Journal of Vertebrate Paleontology, 19: 91-100.
This past Friday, I very happily received the first complimentary copy of my new book, Life Traces of the Georgia Coast from Indiana University Press. After years of field observations, photographing, writing, editing, drawing, teaching, and speaking about the plant and animal traces described in this book, it was immensely satisfying to hold a physical copy in my hands, feeling its heft and admiring its textures and smells in a way that e-books will never replace. So for any doubters out there (and I don’t blame you for that), here is a photograph of the book:
A photograph, purportedly documenting the publication of at least one copy of my new book Life Traces of the Georgia Coast. Photo scale (bottom) in centimeters.
Still, given that a photograph of the book only constitutes one line of evidence supporting its existence, I knew that more data were needed. So of course, I turned to ichnology for help. After all, a 692-page hard-cover book should also make an easily definable resting trace. Here is that trace, formed by the book in the same spot shown previously.
Ichnological evidence supporting the existence of my new book, Life Traces of the Georgia Coast. Using the “holy trinity” of ichnology – substrate, anatomy, and behavior – as guides for understanding it better: the substrate is a bedspread; the “anatomy” is the 6 X 9″ outline of the book, with depth of the trace reflecting its thickness (and mass); and the behavior was mine, consisting of placing the book on the bedspread and removing it. E-book versions of the book should make similarly shaped rectangular traces, although these will vary in dimensions according to the reading device hosting the book.
However, I also admit that hard-core skeptics may claim that such photos could have been faked, whether through the manipulative use of image-processing software, or slipping the cover jacket onto a copy of Danielle Steel’s latest oeuvre. As a result, the best and perhaps only way to test such a hypothesis is for you and everyone you know to buy the book (which you can do here, here, or here). Or, better yet, ask your your local bookstore to carry copies of it, which will also help to ensure the continuing existence of those bookstores for future book-purchasing and ichnological experiments, including books of other science-book authors.
Lastly, just to make this experiment statistically significant, I suggest a sample size of at least n = 10,000, which should account for inadvertent mishaps that may prevent deliveries of the book, such as lightning strikes, volcanic eruptions, or meteorite impacts. Only then will you be able to assess, with any degree of certainty, whether the book is real or not.
Thank you in advance for your “citizen science,” and I look forward to discussing these research results with you soon.
Suggested Further Reading
Martin, A.J. 2012. Life Traces of the Georgia Coast: Revealing the Unseen Lives of Plants and Animals. Indiana University Press, Bloomington, Indiana: 692 p.
After returning from a two-week vacation in California with my wife Ruth, we noticed a cardboard tube awaiting us at home. Intriguingly, the mystery package, which was only about 60 cm (24 in) long and 8 cm (3 in) wide, had been sent by Indiana University Press, the publisher of my new book, Life Traces of the Georgia Coast. We were a little puzzled by it, considering that it couldn’t possibly contain complimentary copies of the book. (As of this writing, I still have not held a corporeal representation of the book, hence my continuing skepticism that it is really published.) What was in this mystery tube?
Front cover and spine of my new book, Life Traces of the Georgia Coast: Revealing the Unseen Lives of Plants and Animals (Indiana University Press). The book, newly released this month, is not yet in stores, but supposedly on its way to those places and to people who were kind enough to pre-order it. But if you didn’t pre-order it, that’s OK: you can get it right here, right now.
Upon opening it, we were delighted to find that it held ten life-sized prints of the book jacket: front cover, spine, back cover, and front-back inside flaps. The cover art, done by Georgia artist Alan Campbell, looked gorgeous, and had reduced well to the 16 X 25 cm (6 X 9″) format, retaining details of traces and tracemakers, but also conveying a nice aesthetic sense. I was also amused to see the spine had the title (of course) but also said “Martin” and “Indiana.” Although I’ve lived in Georgia for more than 27 years, I was born and raised in Indiana, so it somehow seemed fitting in a circle-of-life sort of way to see this put so simply on the book.
Back cover of Life Traces of the Georgia Coast, highlighting a few of the tracemakers mentioned in the book – sea oats, sandhill crane, sand fiddler crab, and sea star – while also providing a pretty sunset view of primary dunes, beach, and subtidal environments on Sapelo Island. (P.S. I love that it says “Science” and “Nature” at the top, too.)
I had no idea what the back cover might be like until seeing these prints, but I thought it was well designed, bearing a fair representative sample of tracemakers of the Georgia barrier islands: sea oats (Uniola paniculata), a sandhill crane (Grus canadensis), sand fiddler crab (Uca pugilator), and lined sea star (Luidia clathrata), as well as a scenic view of some coastal environments. I had taken all of these photos, so it was exciting to see these arranged in such a pleasing way. My only scientifically based objection is that I would have like to see it include photos of insects, worms, amphibians, reptiles, or mammals (these and much more are covered in the book), as well as a few more tracks, trails, or burrows. Granted, I suppose they only had so much room for that 6 X 9″ space, and thus I understood how they couldn’t use this space to better represent the biodiversity of Georgia-coast tracemakers and their traces. (Oh well: guess you’ll have to read the book to learn about all that.)
Inside front and back flap material for Life Traces of the Georgia Coast, which also includes a summary of the book (written by me) and a rare photo of me (taken by Ruth Schowalter) in my natural habitat, which in this instance was on St. Catherines Island, Georgia.
I had written the summary of the book on the inside flap nearly a year ago, so it was fun to look at it with fresh eyes, almost as if someone else had written it for me. Fortunately, I banished my inner critic while reading it, and just enjoyed the sense that it likely achieved its goal, which was to tell people about the book and provoke their interest in it.
In short, this cover jacket symbolizes a next-to-last step toward the book being real in my mind. Now, like any good scientist, all I need is some independently verifiable evidence in the form of tactile data, such as a physical book in my hands. Stay tuned for that update, which I’ll be sure to share once it happens. In the meantime, many thanks to all of the staff at Indiana University Press – who I’ll mention by name next time – for their essential role in making the book happen and promoting it in this new year.
Information about the Book, from Indiana University Press
Life Traces of the Georgia Coast: Revealing the Unseen Lives of Plants and Animals, Anthony J. Martin
Have you ever wondered what left behind those prints and tracks on the seashore, or what made those marks or dug those holes in the dunes? Life Traces of the Georgia Coast is an up-close look at these traces of life and the animals and plants that made them. It tells about the how the tracemakers lived and how they interacted with their environments. This is a book about ichnology (the study of such traces), a wonderful way to learn about the behavior of organisms, living and long extinct. Life Traces presents an overview of the traces left by modern animals and plants in this biologically rich region; shows how life traces relate to the environments, natural history, and behaviors of their tracemakers; and applies that knowledge toward a better understanding of the fossilized traces that ancient life left in the geologic record. Augmented by numerous illustrations of traces made by both ancient and modern organisms, the book shows how ancient trace fossils directly relate to modern traces and tracemakers, among them, insects, grasses, crabs, shorebirds, alligators, and sea turtles. The result is an aesthetically appealing and scientifically accurate book that will serve as both a source book for scientists and for anyone interested in the natural history of the Georgia coast.
A seahorse, of course, is not a horse. But that’s not the only way seahorses differ from horses, in that they leave trails instead of tracks. Intrigued? Yeah, me too. (Photograph by Anthony Martin, taken at the UGA Aquarium, Skidaway Island, Georgia.)
A seahorse (Hippocampus sp.) showing off its lack of swimming skills by moving along the sandy bottom of a tank. Gee, what are all of those meandering and intersecting grooves in the sand and circular imprints? I wonder what made those? Sorry, first guess doesn’t count. (Photograph by Anthony Martin, taken at the UGA Aquarium, Skidaway Island, Georgia.)
A seahorse making tail trails while swimming along the bottom of an aquarium. Notice how the trail would become less linear, wider, and more circular if the tail flops over to one side or another, involving a greater area of the curled end. (Photograph by Anthony Martin, taken at the UGA Aquarium, Skidaway Island, Georgia.)
A close-up of those trails left by swimming seahorses dragging their tails along a sandy surface. Also, check out the overlapping circular “plop” traces on the right, made by the curled part of the tail? (Photograph by Anthony Martin, taken at the UGA Aquarium, Skidaway Island, Georgia.)
