Our first clue of something amiss in the study area was the relatively low abundance of marine turtles in the aftermath of Irma. Turtles congregate in the passes between islands as they ride the tidal flow in and out. Multiple turtles can be sighted surfacing to breath on a given day, provided the weather and water conditions are favorable. We were lucky to see one or two turtles a day during our recent trips, sometimes going a whole day without a sighting. Another clue came from the crab traps used to assess the availability of food as part of our Kemp’s ridley diet studies. Blue, stone, calico, and spider crabs have been collected in these waters but our traps were coming up empty following the hurricane. No groceries on the shelves for the hungry turtles.
Kemp’s ridleys occurring in the Ten Thousand Islands are immature (i.e., non-reproductive) and remain at these feeding grounds for several years. Turtles reach maturity at around 24 inches (60 cm) and, as demonstrated last year by “Shelley,” move to adult habitat in offshore waters of the Gulf of Mexico. Prior to Irma the shell lengths of Kemp’s ridleys captured in our study area ranged 12–22 inches (31–56 cm) with most in the 16– 20 inch (40–50 cm) size range. The few Kemp’s ridleys observed after Irma were considerably smaller, only 11 inches (29 cm) or less. A possible explanation for the size difference is that the larger ridleys with experience feeding in this region have moved to a different area in search of food. The small ridleys we observed were new recruits and have yet to become accustomed to the feeding grounds. Deploying satellite transmitters before the Irma may have provided answers as to turtle movements after the hurricane but hindsight is 20/20. It would be difficult to plan for such an episodic weather event given the vagaries in the tracks and intensities of tropical cyclones during a given year. The last major hurricane to impact this region was Wilma in 2005.
One of the small Kemp’s ridleys observed after Irma deserves recognition, as it was particularly elusive, earning the name “Houdini,” and appeared to remain in the study area from late-October through mid-December. During each of the week-long trips, in a backwater area we refer to as “Ridley Cove,” a very small turtle was observed loafing at the surface. The net was deployed around the turtle following each sighting but none of our four attempts were successful. The turtle was observed in the net during two of the attempts but did not become adequately tangled given its very casual demeanor and apparently slipped through the webbing given its small size. We came across Houdini again on our last day, bobbing at the surface without a care and taunting us as if saying, “Catch me if you can,” but we resisted the temptation to deploy the net a fifth time. Instead, we will let this turtle grow a little larger and perhaps its luck will run out in the not too distant future. Continuing efforts will document the recovery of the Ten Thousand Islands and how the Kemp’s ridleys adapt to catastrophic changes in their feeding grounds.
To learn more about the Conservancy of Southwest Florida’s environmental science work visit www.conservancy.org.