Losing track of Peter and Everett
Editor’s Note: This year, the STPS Board of Directors has funded two satellite transmitters for Dean Bagley, a researcher with the University of Central Florida’s Marine Turtle Research Group. STPS has supported Bagley’s work researching male green sea turtles for several years. This year, the board has named the two male green sea turtles being tracked with the satellite transmitters. The first is named Everett, in honor of longtime STPS volunteer Everett Tindall who turned 91 in June. The second turtle has been named Peter, in honor of STPS founder Peter Bandre and the 35th anniversary of the organization in 2021. Dean Bagley has been providing periodic updates to STPS as she tracks the turtles.
By DEAN BAGLEY
UCF Marine Turtle Research Group researcher
We have stopped receiving signals from Peter’s transmitter now, too. The final map of Peter’s migration and a closeup show his movements and final location. On the closeup, his final location was immediately to the right of the “p.m.” in the time.
Both of the 2021 transmitters stopped transmitting sooner than expected, but I wanted to make sure that everyone understood that while it’s no longer fun for us to be able to watch what they’re doing, the data we received during these few months was still a great contribution to more than one project and to our understanding of adult green turtles, and males in particular.
You’ve heard me say that I’ve tried for years to figure out how to get transmitters to stay on longer, and that I was sure it was something I was doing wrong that resulted in them coming off early. Then I had a transmitter returned to me that still had carapace scutes attached to it. That’s how we learned that it’s not something that is being done wrong, and not that the epoxy wasn’t holding up, as I considered for so long. How long a transmitter stays on a turtle is based on the behavior of the turtle and the habitat in which they reside. The turtle that wore the returned unit had literally beaten the transmitter over and over on rocks/reef to get it off. The damage to the transmitter itself was unbelievable, yet it kept right on transmitting as soon as it was retrieved from the water.
Then there was the turtle that kept the transmitter for just under a year. I think it’s that some turtles are bothered by having something on their backs, while others don’t mind so much. If the transmitter is bothering them and there are rocks nearby, they’ll use the rocks to scratch their backs and to knock it off. My representative at Wildlife Computers has told me that the only turtles he has seen that are harder on transmitters (based on returned units and our shorter duration time) than our turtles are Colin Limpus’ in Australia.
While I continue to hope for longer durations, and do everything I can to make that happen, both of our 2021 turtles went to specific locations and stayed there, which indicates those foraging areas were more than likely home for them. Both males contributed the necessary data for my project that helps us understand how long males remain off the nesting beach(es) during the breeding season and their movements while there, the routes they take to get to their foraging grounds and how long it takes, and where they go, as well as for a large study being conducted by Simona Ceriani at Florida Fish and Wildlife Conservation Commission using stable isotopes. Looking at the carbon and nitrogen in skin, scute or blood gives a ratio of these two substances called an isotopic signature, which relates back to the prey items eaten. Knowing where “home” is for a turtle is vital to that study. She was able to identify the isotopic signature of each tracked loggerhead in her own study* and relate it to signatures of turtles in the foraging grounds. In this way, she was able to identify where untracked loggerheads foraged by comparing their signatures to those of tracked loggerheads. It may be different, or more difficult in green turtles because they are herbivorous, but this is also part of her study. We learn something more with each deployment, even if it’s to tell us that new turtle went to a previously known foraging area. If you deploy 10 transmitters and four of those animals go to one area, you can make an assumption that there are a lot of turtles foraging there. And if they remain in that area, it provides a lat/long for the isotopic “signature” that Simona Ceriani needs to make assumptions in her work. It all works together so that we continue to learn more about adult green turtles, and in our case, males in particular.
*For anyone who wants to learn more about stable isotopes in loggerheads please see the article at Ceriani, S. A., J. D. Roth, C. R. Sasso, C. M. McClellan, M. C. James, Heather L. Haas, R. J. Smolowitz, D. R.Evans, D. S. Addison, D. A. Bagley, L. M. Ehrhart, and J. F. Weishampel. 2014. Modeling and mapping isotopic patterns in the Northwest Atlantic derived from loggerhead sea turtles. Ecosphere 5(9):122. http://dx.doi.org/10.1890/ES14-00230.1
I can’t thank the Sea Turtle Preservation Society enough for your support of this project. It has been a great collaboration.