23 August 2009

Turtle Research

There's an ongoing sea turtle research project here on South Caicos. Two researchers have been studying the effects of turtle harvesting (which is legal here), and SFS has been involved for years. Today I got to join them "on the hunt."

A small Hawksbill.

We went out with two boats, first to Admiral's Aquarium and the surrounding area, then to Shark Alley. Nine of us got into the water and fanned out in search of turtles, while the 10th person drove around in one of the boats facilitating communication between us and shuttled people to where there was a sighting. We had very good visibility today (probably around 200 feet or more) and we had timed it for minimal currents, so conditions were favorable.

It took quite a while before the first sighting, however. Will spotted a considerably large Green Turtle and we all started to chase after. The strategy is to tire it out by taking turns and by using the boat and, when it's slowed down enough, dive down and grab it by the carapace behind its head and in front of its tail. You can't just reach out and pick it up, though, it requires a really sudden snatch to actually get a hold of it. Green Turtles are bigger and have significantly higher endurance (I was told), so they tend to be harder to catch. And this one managed to get away. In fact, I never even saw it.

In trying to locate it, however, I spotted a small Hawksbill and called over for assistance. I followed it for a few minutes, but eventually lost it. I found out just after that, that nobody had come to help because they were on the trail of a second small Hawksbill! Just as I arrived on the scene, I saw John (probably the strongest swimmer of all of us) dive down and press the young turtle to the seafloor. He then grabbed onto it by the sides of its shell and brought it, struggling, to the surface. Hawksbills, I am told, tire significantly more quickly.


We got it in the boat and started taking data immediately, so as to minimize stress to the animal. He flapped his flippers quite a bit when he was being handled, but seemed calm when sitting undisturbed. We took several standard measurements of the carapace, tail, and head; a genetic sample of flesh (the snip didn't seem to hurt it one bit); a blood sample (using the same type of needle you'd use on a person); and a shell sample. We then scanned it for an implanted microchip tag (the same sort they use on dogs these days), implanted a microchip tag (because our scan didn't find one), attached two of the old-fashioned external fin tags, and weighed it. I felt bad about all the stress and pain we were causing it, but I tried to convince myself that it was for the good the entire turtle population.

Measuring straight carapace width.

A turtle's-eye view.

Hawksbills have narrow heads and pointy beaks like a hawk.

Implanting the microchip.

Attaching the flipper tag.

Posing prior to release. You can actually feel the shell expand and contract as it breaths!

Almost home.


Since we had finished more quickly than we had expected, we decided to have a quick look at Shark Alley to see if we could get a second turtle. A few of us jumped in at the point with the plan to swim back towards the mooring, where the boats would be. Shortly after getting in we spotted an Eagle Ray (as we often do at Shark Alley). We followed it to make observations and get photographs for another ongoing research project. Just a few seconds later I saw another one, and called over to the others that there were two. I was wrong. It was actually 4 more! I could hardly believe it. The first one joined up with them, and they all swam over a large coral outcropping. We followed excitedly and were blown away to see 3 more! They all joined up, forming a school of 8 Eagle Rays!!! I remembered reading in our ID book that they occasionally pair (which we often see) and on rare occasions, school.

Swarm of Eagle Rays

It was fantastic to see. And, because of their numbers, they were much less afraid of us. Usually they are wary of people and are frightened off by the vigorous kicking of snorkel fins that is required to keep up with them. But now we were able to follow them quite closely, and did so for probably 10 minutes. They are one of the most graceful and beautiful animals we see here. Slowly they broke off and went in different directions (alone and in pairs), but they all stayed in the same general area, circling as they often do, so we got to watch them for quite a long time. One of the larger ones, I noticed, had an injured wing. It curled at the end (3 or 4 inches) and appeared to be shriveled. It didn't seem to be bothered by it, so hopefully it will recover. We also saw a small Caribbean Reef Shark in the mix, which on any ordinary day might warrant a more detailed description here.

Another shot of all 8 of them.

In all the excitement and commotion caused by the Eagle Rays, I didn't even notice that John had nabbed his second turtle of the day! The big Green we were chasing before - Will was able to identify it by the tag it had on its back left flipper. This was my first close look at a Green Turtle. I didn't expect its shell to be so brilliant, an olive green color with streaks of light and dark. Hawksbills are the ones famous for their impressive shell (the reason they are the most endangered worldwide). We were all feeling a bit worn out and hungry, so we collected the data and samples and released her as quickly as we could.

Old tag from a previous capture.

Green Turtles are much bigger, up to 200kg. This one was about 20kg.

What a beautiful green shell.

Green Turtles suffer from a virus that causes cancer. The growths in the upper right of this photo might have been small tumors.

Using the sensor to detect a microchip.

Measuring curved carapace length.

The Green Turtle was much calmer.

Notice the algae growing around its neck.

Soon to be released.

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