At one o’clock this morning as we were patrolling I spotted a dark patch at the edge of the water. Sure enough, it was an emerging Olive Ridley Sea Turtle. We backed off and sat down at a distance to wait for her to finish emerging. She was about three feet long from nose to tail and her domed shell was maybe 15″ high.
Once she had crawled up to the edge of the beach where the vegetation begins, we circled around and sneaked up behind her. She totally ignored us. She was digging a deep hole underneath her rear end with her hind flippers. You wouldn’t think that a sea turtle’s hind flippers would be particularly dexterous, but she would bend her flippers into an “L” shape, reach down deep, and carefully lift out a bit of sand using her left and right flippers alternately. The three of us lay on the sand right behind her and watched using the red light of our headlamps.
Then she stopped digging and started to lay eggs. Sean handed me a counter, which is a little mechanical device with a button and a display for tallying eggs. Lying on the ground just behind her, I peeked underneath her and every time an egg popped out I added it to the count. This wasn’t easy because often they would come out two at a time. She laid 78 eggs. They looked like wet, glossy white ping-pong balls; perfectly round. While I counted Sean and Dean went forward to measure her shell and give her a flipper tag, since she didn’t have one yet. All this is called “working a turtle” and it’s best done in a team of three.
When the eggs stopped coming, she backfilled the hole with sand, all using her hind flippers. Then she began her “dance”: she kind of stamped on the sand, left foot, right foot, left foot, etc., all the while shimmying back and forth and swaying her shell. I guess she does this to pack down the sand. We left.
I have a new appreciation for turtles! I’m going to have a special feeling about them the rest of my life.
This is my last blog form Costa Rica. I sure am grateful to the Earthwatch Institute for giving me this opportunity.
The Hatchery is a place where we move turtle nests to if they’ve laid their eggs in a bad spot. It is a fenced-in patch of sand with some equipment.
Volunteers guard the hatchery all night, every night. I’ve done a couple of shifts. It’s pleasant, low-pressure work. You sit in the dark in the middle of the hatchery with a companion and a mosquito coil for company. The sky is really black and the Milky Way is really bright. There is usually a cool breeze. I spend a lot of my time on my back, studying the stars through my binoculars. Orion, the Pleiades, and Jupiter are especially good viewing. The two-way radio is on so you can hear the patrols on the beach telling each other where they are and if there are any turtles. Since the hatchery is the end point for two of the beach patrols, volunteers on patrol drop by about once an hour for a visit. Every half hour you check the nests to see if any baby turtles have crawled out of the sand, but this rarely happens. Once in a while you scan the fence line with your flashlight for raccoons. After five or six hours somebody comes to relieve you.
Yesterday we were in the hatchery to excavate a nest that never hatched. This happens sometimes; nobody knows exactly why. We dig up all the eggs (they are buried arms-length deep) and open them up to see how far they developed. For these ones, they didn’t get very far. Maybe they were too hot, or too dry, or the turtle just wasn’t very fertile. There are some things we still don’t understand about turtle reproduction. We have a lot of successes at the Hatchery, though.
We went up the estuary of the Parque National Marino las Baulas de Guanacaste (the national park we work at) in a small boat to see what’s there. An estuary is a place where fresh river water meets salt water from the ocean. The resulting partly-salt water is called brackish.
This estuary is lined with mangroves. Mangroves are small trees that can grow with their roots in salt water. They are found all over the world on tropical coastlines. Their roots form big tangles in the shallow water which provides excellent cover for birds, small fish, and all kinds of wildlife.
This estuary has crocodiles, howler monkeys, parrots and all kinds of wadding birds.
There are seven species of sea turtles: Green Turtles, Hawksbills, Olive Ridleys, Kemp’s Ridleys, Loggerheads, Flatbacks, and Leatherbacks. Leatherback turtles are the heaviest reptiles in the world, and the most widely distributed. They are found all over the Pacific, Atlantic and Indian Oceans from the tropics to the polar seas north of Scandinavia. They are not very closely related to other sea turtles. They lack hard shells, but have a stiff rubbery skin with seven knobby ridges running fore and aft. They are somewhere between warm blooded and cold blooded: they have body temperatures that are typically higher than their surroundings, but their body temperatures are not constant. They eat jellyfish, which are very low in nutrients. So they eat a lot: up to 200 pounds of jellyfish per turtle, per day. Jellyfish, in turn, eat commercially important fish so leatherbacks are important ecologically and even economically. Tourists also pay to see them when they come ashore.
Three of the seven species lay their eggs here on Playa Grande, our beach, but this project is really all about the Leatherbacks. In the late 20th century over a thousand leatherbacks nested here every year. It was the biggest leatherback nesting beach in the world, but almost all the eggs were being taken by organized egg harvesters. So far this season only twenty leatherbacks have shown up. They’ve had two decades of protection but it probably takes longer than two decades for a female leatherback turtle to reach sexual maturity, so all those baby turtles that were saved aren’t laying yet. (Former egg poachers are now on board as scientific collaborators, which is actually a common story in conservation biology.)
Part of the research going on here has to do with the optimal conditions for their nests. Nests can get too hot or too dry for the eggs to survive. Oxygen, humidity and bacteria in the sand all play a role in determining whether eggs will hatch or not. Because of bacteria, the scientists here clean all of the sand out of the hatchery annually to a depth of one meter and replace it with fresh sand. This is a ridiculous amount of work because the hatchery is as big as a small house lot. Hotter temperatures result in a higher ratio of females to males; lower temperatures have the opposite effect. Part of the research is just basic counting: number of nests, number of turtles, sizes of turtles, number of eggs, number of seasons per turtle, etc.
Once a turtle has hatched it is supposed to crawl down to the water’s edge, but bright lights from houses or towns will attract it and trick it into going in the wrong direction. Once it is in the water, it faces other threats: getting caught in a fishing net, or eating plastic. Ninety percent of leatherback turtles have pieces of plastic in their stomachs. A plastic bag floating in the water looks just like a jellyfish. Maybe we should ban disposable plastic. We have plenty of other good reasons to do that.
I can’t photograph the adult leatherbacks on the beach because it is dark and I can’t use a flash. But they are BIG!! Like boats. The web site of the Leatherback Trust has some good pictures. http://www.leatherback.org/
There’s a lot of wildlife here. Costa Rica has over 400 species of reptiles and amphibians. In our backyard there’s a big iguana who spends his days sunning himself on his favorite corner of the shed roof. If you get too close he becomes agitated and does push-ups.
I asked the biologists his name and they said he didn’t have one! That had to change. We settled on Cteni Tom, pronounced “Teeny Tom.” (The C is silent.) That’s because he is a Spinytail Iguana, Ctenosaura similis. They are plant eaters, active by day.
Tom is a handsome adult with a big dorsal crest – the spikes along his back. He is about a foot and a half long. A few other iguanas share his space, but not for long. The special corner is his.
The beach in front of our Field Station is important. Almost half of the leatherback turtles in the eastern Pacific nest here. In the 1970s, 1980s, and 1990s nearly all the eggs were dug up by humans and eaten. The beach was made into a national park in the mid-1990s and now volunteers and biologists patrol the beach every night from October through March when the turtles are nesting. Our vigilance helps deter poachers. It’s actually illegal for anyone to be on this beach at night, unless you’re an Earthwatch biologist, a professional guide or a park ranger or you are accompanied by one of those people.
There are three species that nest here: Leatherbacks, Olive Ridleys, and Black Sea Turtles. The leatherbacks are really huge.
We walk in teams of three; one staff biologist and two volunteers. We wear red headlamps but keep them turned off unless we find a turtle. We wear long pants to protect against sand fleas and athletic shoes to protect our feet from injury in the dark and carry water, bug repellant and scientific equipment. We start three hours before high tide and continue until three hours after high tide, no matter what time of the night high tide is.
We are divided into several teams; last night I was doing the “north” portion of the beach. We walk briskly down the beach for about twenty minutes on the wet sand. Then we sit still for twenty minutes. Then we walk briskly back the way we came. Another break. Back and forth, back and forth, we crisscross the same portion of beach for six hours in twenty minute sweeps. At the ends of our segment we occasionally meet other groups. It’s both strenuous and contemplative, because it’s very dark and the stars are really bright. There is phosphorescence in the water; bright specks of it are lying on the sand like little glowing jewels. During our breaks we look up at the sky and see shooting stars. The surf never stops.
We are looking for turtle tracks. When the turtles crawl out of the surf, they leave a big dark track in the sand. If we cross one, we follow it up the beach and find the turtle. If she is laying her eggs in a good spot somebody lies down on the sand just behind her and counts the eggs as they fall into the hole she has dug. If she is new to this beach, she gets a flipper tag installed. If she’s not new, we read the tags she is wearing.
Doesn’t she mind all the attention? It doesn’t look that way. The biologists I am with say that she is in a “trance”; her body is flooded with egg-laying hormones. We stay behind her, speak in hushed voices and use only red light which she can’t see well. She appears not to notice us.
If she is laying her eggs in a “doomed” spot, we catch them as they come out of her and move them to the Hatchery. The hatchery is a fenced-off square of sand high up on a dark, quiet section of the beach. A person is minding the hatchery at all times of the night. During the day we check every half hour in case baby turtles start to hatch. When they do we put them in a bucket and let them go at the water’s edge that evening. At night the job is to protect the hatchery from raccoons, who are always trying to come in and dig up the nests.
What makes a spot “doomed”? For one thing, if there are lights nearby the baby turtles will try to crawl towards them when they hatch instead of down the beach towards the water. They are programmed to crawl towards light near the horizon, because in a state of nature this would be the line of surf lit up by starlight. Obviously, if there are lights from development nearby the turtles try to go to them and they never make it to the water.
Besides night patrols and hatchery shifts, a team patrols the beach every morning, starting just before dawn, to see if the night patrols missed any nests. So there is almost always someone working on the beach, around the clock. We get together for two meals a day, at 11:00 AM and 6:00 PM; these are the only times that nobody is working (except whoever is on hatchery duty.)
This project is the Earthwatch Institute’s longest-running project that is still in operation – it’s 27 years old. But, the work we do doesn’t photograph well. You can’t use a flash on the beach at night.
I had three flights, each with a long layover, so it took almost a day to get here. In the Los Angeles airport I met two other teachers who received Earthwatch Teach Earth Fellowships like me: Justine Hochstaedter and Dean Lorenzo, both from the San Francisco Bay Area.
I got here in time for dinner. At the Goldring-Gund Marine Biology Field Station, we work all night. So there wasn’t time to post a blog, sleep, even shave! I spent last night patrolling the beaches. There is a lot to tell about that; and no time to tell it now. But when I first arrived everyone was looking into a bucket of just-hatched Olive Ridley sea turtles.
Later on I got to carry them down to the beach and let them go.
So, enjoy these pictures until I have time to post more.