Grant: 07-021R
Project Title: Satellite Tracking Large Green Turtles
Project Manager: Dean Bagley
Organization: Inwater Research Group (Non-Profit Organization)
Grant Amount: $20,000.00
Completion Date: 2011-01-12

Summary: Even after decades of study, much remains unknown about green turtle life history. In Florida, small to mid-sized green turtles are abundant in nearshore waters while the largest immature animals between 70 cm and 90 cm are rarely seen. Adult green turtles are found foraging in the lower Florida Keys (Schroeder et al., 1996). Recently our group made an extraordinary discovery in an area west of the Marquesas Keys in Florida. We have identified, for the first time in the United States, a large foraging area shared by large subadult and adult green turtles. Using Fast-GPS satellite technology and sonic tags we intend to follow the local movements of these immature and adult green turtles to better understand home range and habitat use. If immature turtles migrate to other waters, we will learn their routes and destinations. Should the adults migrate to the nesting beach, we will learn which beaches. To the best of our knowledge, no one has tracked adult green turtles from foraging grounds to the nesting beach. The information gained from this study should allow managers to make important conservation and management decisions for this endangered species, and provide us with greater insight into the life history of green turtles.

Results: Six green turtles were hand-captured west of the Marquesas Keys and GPS Fast-loc transmitters (Wildlife Computers model MK-10) were deployed on one adult male and one adult female, one large subadult male and one large subadult female, and two smaller subadults of unknown gender. Straight carapace length ranged from 70.4 cm to 101.5 cm, mean was 86.9 cm, SD 11.7 cm. When we began this study, we assumed that these turtles would leave the relative exposure of the extensive grass flats to find some sort of cover or protection at night. We examined differences in day vs. night movements. Only one turtle showed any type of day/night pattern. There did not appear to be any difference in depth between the two areas. These satellite data suggest that these green turtles are resident in this area and we consider it a critically important foraging ground for green turtles that nest in Florida (Barbara Schroeder, unpublished data), Costa Rica and Mexico (Bresette et al. 2010). It is interesting that this adult foraging ground also supports large subadult turtles, suggesting that large subadults recruit to adult foraging grounds to complete maturation. Only continued, long term monitoring of this important feeding area will provide insight about these lesser understood size classes in foraging areas.