Nearshore Orientation Preferences of Loggerhead Sea Turtle (Caretta caretta) Hatchlings in Kyparissia Bay, Greece

Orientation behaviors of loggerhead sea turtle (Caretta caretta) hatchlings during their initial offshore migration in the Atlantic Ocean have been well described and involve visual, mechanical, and geomagnetic mechanisms. The Greek nesting population of C. caretta is genetically distinct from Atlantic sea turtles, and little is known about their initial dispersal movements in the Mediterranean Sea after hatching. The goal of this study was to examine the initial swimming paths of hatchlings at Kyparissia Bay, the second largest nesting ground in the Mediterranean. It was hypothesized that loggerhead hatchlings would orient themselves in a similar and non-random direction employing a course corrective behavior and that the average swimming speed would be lower than that of the Atlantic population due to morphological and evolutionary differences. This study was conducted over 13 nights in the 2011 hatching season. Directional and distance data were obtained by a shore-based observer who monitored hatchling swimming paths (n - 91 hatchlings) with a spotting scope (20-60x) up to a maximum distance of 200 m offshore. Distance and direction data were collected at one-minute intervals for an average of 26 min per hatchling. Speed and direction of the local currents during hatchling dispersal into the sea were also obtained. Hatchling path and swimming speed were calculated and their path characteristics were compared to potential environmental orientation cues including longshore current speed. The characteristics of each path were examined for entire path average heading and speed, as well as initial and final average heading and speeds. Our results indicate that hatchlings of Kyparissia Bay, Greece course corrected to remain in a westward (offshore) direction. Their offshore migration speeds were initially higher, perhaps to avoid predation, and then decreased within the time of observation, but overall hatchlings were slower than the Atlantic population. These results add to the understanding of Greek C. caretta hatchling movements post-emergence and may be useful for management and conservation