Novel GPS tracking of sea turtles as a tool for conservation management

We used recently developed, low-powered, TrackTag™ GPS loggers to track the movements of female loggerhead sea turtles (Caretta caretta) at the largest breeding population in the Mediterranean (Zakynthos, Greece). Three turtles were tracked for a total of 73 days in May and June 2006, during which time 3753 GPS locations were obtained after filtering outliers (51 per day per turtle). The diving behaviour of these three turtles and three others was also monitored using time-depth recorders (TDR). The GPS data revealed that all three turtles spent most of their time in shallow water (< 4 m sea bed depth) very close to the shore (< 200 m), primarily ranging along an 18.5 km section of coastline. These observations were corroborated by TDR data acquired from all six turtles and frequent first-hand sightings of turtles close to shore during the breeding period. Comparison with random crawl movement models indicated that two of the tracked turtles moved with a similar non-random pattern, suggesting common biophysical processes might be driving their movements. The movement and depth data that we collected both suggest that existing legislation to safeguard sea turtles within this protected region may not include the most critical habitats for female loggerhead sea turtles during the breeding period. Our study demonstrated the feasibility of using GPS tracking to investigate fine-scale movements of a marine vertebrate, illustrating the value of GPS tracking for wildlife conservation management. © 2007 Elsevier B.V. All rights reserved.