Green sea turtles having strong nesting season on Sanibel
The first green sea turtle was tagged on June 5, east of Bowman’s Beach, on the west end of Sanibel. Since then four more were tagged on Sanibel making the Green Sea Turtles in Southwest Florida program a huge success for the first year.
The Sanibel-Captiva Conservation Foundation partnered with the Conservancy of Southwest Florida this year to tag green sea turtles after Biologist Dave Addison asked SCCF Sea Turtle Coordinator Kelly Sloan if they wanted to participate in the program. The sample size doubled to eight when Mark Banks became a donor.
“We were skeptical that we would get them all on . . . hopeful, but skeptical,” Sloan said. “But, we have seven out of eight on already.”
As of last Tuesday, two green sea turtles were tagged with satellite trackers on Keewaydin Island and five on Sanibel.
SCCF has a nighttime tagging crew monitoring the beaches seven days a week to tag loggerhead turtles with flipper and pit tags, as well as taking measurements. So far this year, the crew has encountered 202 loggerheads, representing 135 individuals, meaning they have had lots of recaptures providing great data.
There has been 20 green sea turtle nests reported on the island.
Sloan said this year, they anticipated green sea turtles to come ashore to lay nets since they nest biannually, so it was a great year for satellite tagging.
“They are out there at night and actually seeing females,” she said of the nighttime tagging crew spotting green sea turtles.
With the loggerhead and green sea turtle tracks being quite different, as well as different nesting characteristics, the crew is able to identify each species. Sloan said green sea turtles use symmetrical movements while crawling on the beach and a loggerhead crawl like babies.
“Green sea turtles also have a tail drag because their tails are a little bit longer, so you can see a tail drag down the center,” she said. “The alternating movements of the loggerheads makes their crawl look a little bit wavier,” she said. “If you don’t see the female you can tell based on their tracks.”
Another difference, a green sea turtle spends a long time covering their nest to camouflage it from predators.
“It ends up looking like a huge crater on the beach like a bomb went off,” Sloan said. “So when they nest it is very obvious.”
With the greens spending a great deal of time on the beach, it plays to SCCF’s advantage because it is more likely they will encounter them.
Two of the five green sea turtles were found at 5 a.m. nesting.
Sloan has been on site for each of the taggings, as well as Technician Andrew Glinsky.
“Andrew’s played a really key role in this project too. He’s done such a good job of getting all the supplies together and keeping on top of everything,” she said.
Sloan said it’s been interesting to watch so many greens nest.
“We usually just get to see it from the prospective of the morning survey when you go out and see this huge crater on the beach and the rest is left up to your imagination. But now we get to put the two pieces together and see exactly the behavior of these turtles,” Sloan said.
The greens, she said, have different personalities.
“Loggerheads have, for the most part, a very stereotypical nesting behavior. They tend to do things the same. The greens do have a lot of personality. They all do things a little bit differently and they are much more skittish than loggerheads. We have to be very careful about minimizing our presence on the beach and allow them to complete their nesting process,” Sloan said.
The very first green sea turtle, Sloan was lucky enough to find crawling out of the gulf as she was crawling onto the beach at 10 p.m. The tag was not placed on the turtle until 1 a.m.
The goal of the project is to look at their post nesting movements, which will help in management.
“We have a really good idea of what loggerheads do after they nest in Southwest Florida because there has been several projects at the Conservancy of Southwest Florida, up in Gulf Shores, Alabama putting satellite tags on loggerheads to look at their migration and foraging grounds, but no one has done it with greens yet,” Sloan said.
She said commercial fishing and the accidental captures in fishing nests is the primary source of fatality for sea turtles. Sloan said if you know there are high concentrations of sea turtles in an area during a certain time of year, you can close that area to certain fisheries.
“You can use that information for various management strategies,” she said. “That has been done for loggerhead sea turtles.”
So far, by attaching the satellite transponders to the five turtles, Sloan said they have found the green sea turtles nest on other beaches, instead of returning to Sanibel.
“We assumed kind of that they would come back to our beach to nest because they nest every 10 days. We have found that a lot of them are going to other beaches to nest,” she said. “That part is fun to see.”
Green sea turtles lay a clutch of about 136 eggs, whereas loggerheads lay an average of 110 eggs.
The community can follow the green sea turtles that have been tagged by visiting www.movebank.org. Click on tracking data map and search for Green Sea Turtles in Southwest Florida.
“I never want the season to be over, but at least we have something to look forward to,” Sloan said of the data that will be collected on the greens with the satellite transponders. “We are hoping that they transmit for at least a year.”