Category Archives: Turtles

Sand tracks

“In every outthrust headland, in every curving beach, in every grain of sand there is a story of the earth.” Rachel Carson, writing in Holiday magazine, 1958.

From the curving beach of St Catherines Island, another blog post in the grapheme series (parts I, II, and III). Sand scribblings. For the full coastal Georgia effect, view in a steam room with the heat turned up to one hundred degrees. Click on any image for the slideshow:

Loggerhead sea turtle necropsy, and a second chapter

A memento mori, delivered from sea to sand, from Poseidon to Psamathe. The turtle washed onto the Atlantic shore of St Catherines Island. Given the parlous state of sea turtle populations, every breeding adult is important, so a vet from the non-game division of the Georgia wildlife agency came to the site to determine the cause of death.

The turtle been floating dead for a week or so before washing up. The large number of barnacles on her shell indicate that even while alive, she’d been slowing for some weeks.

2015-06-12 turtle necropsy 0022015-06-12 turtle necropsy 003The vet gave the carcass a check with the pit-tag scanner to make sure that this turtle had not been previously tagged by turtle biologists. No signal.

2015-06-12 turtle necropsy 008The esophagus, covered in downward-pointing rubbery fingers. Loggerhead turtles swallow crabs, then grip them in their throats as they expel excess water.

2015-06-12 turtle necropsy 015There were no fish hooks or plastic debris in the gut, only remains of crustacea. A horseshoe crab leg from the large intestine:

2015-06-12 turtle necropsy 017Microbial decomposition was well-advanced (stand upwind…), but the “turtle soup” (as the vet called it) revealed no obvious cause of death.

2015-06-12 turtle necropsy 010The turtle was likely born on this beach or one closeby. She traveled the Atlantic gyre as a youngster, then wandered the ocean for at least thirty years, perhaps as many as sixty. To misquote the Bard, food for vultures, brave turtle: Fare thee well, great heart.

They have their exits and their entrances, And one turtle in her time plays many parts… an exit, yes, but also many entrances:

crawlt…the crawlway of a sister or cousin of the deceased, oaring up the beach to dig a nest. She chose a poor spot, one that would get flooded, so the St Catherines Island Sea Turtle Program relocated the nest to a safer place. One of the traveling eggs:

turtle eggHopefully the egg, and its one hundred siblings, will hatch and then swim out to the Atlantic gyre in mid-August.

Here is a fabulous figure from a recent article by Katherine Mansfield and her colleagues on satellite-tracked loggerhead turtle hatchlings (source: Mansfield, K. L., Wyneken, J., Porter, W. P., & Luo, J. (2014). First satellite tracks of neonate sea turtles redefine the ‘lost years’ oceanic niche. Proceedings of the Royal Society of London B: Biological Sciences, 281(1781), 20133039.). The upper map is colored by depth, the bottom one by water temperature. Lines show the paths of individual hatchlings.

turtle map

Turtle tracks

Tracks left by young snapping turtle. Body length, about two inches. May 1st, Sewanee TN.

Tracks left by young snapping turtle. Body length: about two inches. May 1st, 2013, Sewanee TN. Habitat: puddle on gravel road between Alabama and Willie Six Avenues.

loggerhead crawl2

Tracks left by adult female loggerhead sea turtle. Body length: about forty inches. July 6th, 2012, St Catherine’s Island, GA. Habitat: large salty puddle between America and Africa.

Goodbye loggerhead sea turtle hatchlings…see you in the year 2042

Two nights ago, Gale Bishop has his colleagues at the St Catherine’s Island Sea Turtle Conservation Program were kind enough to invite the Sewanee Island Ecology Program crew along on the year’s first release of baby turtles. These little hatchlings all came from the same nest, a nest that was dug out by hand (not flipper) to save it from a predatory ghost crab that had started to munch its way through the clutch. The crab got three; one hundred and fourteen were released.

The turtles were kept through the day in a cooler (to keep them at the temperature of their sandy nest deep in a dune), then taken to the beach at sunset. This timing mimics the natural rhythm of hatching: the youngsters emerge at night when they are a little safer from the heat of the sun and from beach-hunting predators. They dig their way out of the nesting burrow high on the beach, then crawl down the sand (they all know which way to go) into the breaking surf. Once in the water, the turtles swim away, surfacing for gulps of air, then head out to the open ocean.

Many of these young turtles will follow the Atlantic gyre, passing Iceland, then Northern Europe, then Portugal, the Azores, finally ending up in the Sargasso Sea where they will live until they reach sexual maturity in about thirty years. Some will avoid the swirl of the Atlantic and swim directly to the Sargasso Sea. The “long and perilous journey” cliché applies here: one in a thousand will survive to breed. When mature, the females come back to shore to lay their eggs; the males never again set foot on land.

So if I’m lucky enough to reach my seventies, I’ll make a return trip to this island. If the hatchlings survive natural predators, legions of fishing boats (up to thirty massive shrimp trawlers at a time off this beach alone), and an ocean filled with tangling, choking garbage, I’ll greet again the turtles that we released onto the beach today. What will the beach be like in thirty years? It is presently eroding at two meters per year, a rate that will accelerate in a world with warmer, stormier, higher seas. But I hope some sand will still be here to greet the mothers as they crawl ashore.

Letting these youngsters go was an emotionally charged occasion. Turtles are ancient creatures, one hundred and forty million years on this OceanEarth, older than the flowering plants, older than most dinosaurs and mammals, and older than Homo rapaciens which has been around for a mere turtle’s blink, two hundred thousand years. Yet in the short time that humans have been here, we’ve pushed all sea turtle species to the edge of extinction. The vulnerability of the little hatchlings and the long long odds that each one faces, odds worsened considerably by the gutted state of the oceans, is profoundly sad. But the vigor and determination of the little turtles is an incarnation of hope, optimism scribed in turtle flesh: damn the odds, I’m headed down this beach with flippers whirring, then I’m taking to the dark ocean with gusto to swim into my fate. All this produces a powerful combination of feelings and thoughts in the watching bipeds. Several of us had tight throats and drops of ocean water in our eyes as we watched the turtles leave.

The photos below include a few from earlier in the week to illustrate the nesting process, then some of the release.

Tracks left in the sand by a mature female ascending the beach to lay her eggs. They do this at night when heat and predators are less of a problem.

Loggerhead turtle nest. This one is being moved upshore to keep it out of the drowning high tides.

The nest chamber is dug by the female with her back flippers.

Loggerhead sea turtle egg. Unlike many reptilian eggs, sea turtles egg shells are partly calcified, giving them the feel of a bird egg.

Ghost crab — they live in deep burrows and love to eat turtle eggs.

The new nest site is protected with a wire mesh. This keeps raccoons and feral pigs from digging up the eggs.

The cooler of turtles arrives…

…and is admired.

Loggerhead-to-head

The following photographs are from the release of the turtles onto the beach. The hatchlings propel themselves down the beach on their flippers, then get caught up in the breaking waves.

Gopher tortoises on St Catherine’s Island, GA

I’m spending ten or so days teaching on St Catherine’s Island, a coastal barrier island south of Savannah, GA. The island is swarming with interesting creatures; I’ll highlight just one in this post, with more to follow.

The gopher tortoise (Gopherus polyphemus) is the only “true tortoise” (Family Testudinidae) in eastern North America (the other shelled critters here are all turtles of one kind or another, even the terrestrial box turtle whose kinship is much closer to pond turtles than it is to tortoises). Gopher tortoises dig very long burrows in which they spend most of their time. Some burrows are four or five feet deep and twenty feet long. These subterranean homes help the animals escape the worst of the heat and the cold. They also provide a safe space when fires roar through the open piney forests that is the preferred habitat of the species. These fires help to maintain the savannah-like structure of the forest, but they are obviously also dangerous to resident animals.

The population of gopher tortoises on St Catherine’s came from the mainland. They were moved here when a commercial development destroyed their habitat. Since then, the tortoises here have thrived and bred. They live in a large pasture that is maintained as an open savannah. From the surface, all that is visible are the sand piles around the entrance to each burrow. It is seriously hot here at the moment, so the animals usually stay below in the cool.

Gopher tortoise burrow with apron of sand. The females lay their eggs in this apron.

The hole is tortoise-shaped…

Bess Harris, a graduate student at the University of Georgia, is on the island studying the tortoises. She kindly took some time out of her afternoon to talk about her work and show us some of the animals that she was fitting with radio-transmitters.

This one is eight years old. She/he has many more decades of life to come, hopefully.

The tortoises were surprisingly fast (Aesop never saw a gopher tortoise, it seems) and had to be grabbed and retrieved as they paddled away.

Radio transmitter.

The front legs are flattened: great shovels.

Not only flattened, but strong. A full grown tortoise (about 20 lbs) can out-pull a human hand. This one is only half grown and inflicted no bruises.

Beautiful patterns in the keratin shell.

A strange potato

I came across this odd potato while digging the last row of the early crop of potatoes. The spud in question was mottled brown and yellow; its skin seemed rather tough.

I grubbed around with my hand and pulled up the prize. He regarded me with a grumpy red eye.

This eastern box turtle had dug himself down into the mulch that I hill up around potato plants. He was a good six inches down, where the soil is still somewhat moist and cool. All this happened several days ago. I replaced him, carefully covered him again with soil, and marked the spot so that I would not spear him with my garden fork. He’s still there: when I wiggle my fingers down I can touch his shell.

The technical name for this kind of summertime dormancy is estivation (aestivation in the Old World). The turtle is conserving water, saving energy, and waiting out this interminable heat. Which animal is smarter: the one snoozing in the shady soil or the one toiling to earn his potatoes with the sweat of his brow? I have my opinion on this; I’ll let you form your own.

The potato plant that he cuddled up to yielded the biggest load of spuds that I’ve even seen from a single plant (boastful evidence below). So, this fellow either brought good vibes with him or he has a taste for moisture that led him to the most productive spot in the garden. Both, perhaps.

Mayapple fruit

On a recent walk in Shakerag Hollow I ran across this mayapple (Podophyllum peltatum) plant lying prostrate on the ground, its fruit resting on the leaf litter surface. This is box turtle food. Turtles love the fruits and serve as seed dispersers for the plant. The fruit is the size of a small lemon.

Mayapple contains chemicals that are used in anti-cancer drugs, so our health depends, in small part, on the ecological services provided by box turtles. One more reason to drive carefully? I moved this fellow (red eyes, domed plastron = a male) out of the way last week…