Home range and habitat use of juvenile Atlantic green turtles (Chelonia mydas L.) on shallow reef habitats in Palm Beach, Florida, USA

Many animals, including sea turtles, alter their movements and home range in relation to the particular type and quality of the habitat occupied. When sufficient resources are available, individuals may develop affinities to specific areas for activities, such as foraging and (or) resting. In the case of green sea turtles (Chelonia mydas L.), after a number of years in the open ocean, juveniles recruit to shallow-water developmental habitats where they occupy distinct home ranges as they feed and grow to maturity. Our goal was to study the habitat use and home range movements of juvenile green turtles along a shallow, worm-rock reef tract in Palm Beach, Florida. Six turtles, measuring from 27.9 to 48.1 cm in straight carapace length and from 7.2 to 12.6 kg in mass, were tracked via ultrasonic telemetry from August to November 2003. Upon capture, each turtle's esophagus was flushed via lavage to determine recently ingested foods. In addition, four turtles were recaptured and fitted with a time-depth recorder to study dive patterns. Home range areas measured with 100% minimum convex polygon and 95% fixed kernel estimators varied from 0.69 to 5.05 km super(2) (mean=2.38 plus or minus 1.78 km super(2)) and 0.73 to 4.89 km super(2) (mean=2.09 plus or minus 1.80 km super(2)), respectively. Home ranges and core areas of turtles were largely restricted to the reef tract itself, and showed considerable overlap between food and shelter sites. The mean number of dives during daylight hours (0600-1800 hours) was 84 plus or minus 5.0 dives, while the mean during night hours (1800-0600 hours) was 39 plus or minus 3.0 dives. Dives during the day were shallower (mean=3.20 plus or minus 1.26 m) than dives at night (mean=5.59 plus or minus 0.09 m). All six turtles were found to have a mixed diet of similar macroalgae and sponge fragments. Our results reveal that juvenile green turtles occupy stable home ranges along the nearshore worm-rock reefs of Southeast Florida, during the summer and fall. Determining which habitats are used by green turtles will assist conservation managers in their global effort to protect this endangered species.