High resolution Fastloc-GPS tracks reveal the complexity of sea turtle migrations

The emergence of Fastloc-GPS technology has enhanced animal tracking accuracy via Argos, allowing the investigation of detailed movement patterns. To illustrate Fastloc-GPS usefulness and determine its typical accuracy, we... [ view full abstract ]

The emergence of Fastloc-GPS technology has enhanced animal tracking accuracy via Argos, allowing the investigation of detailed movement patterns. To illustrate Fastloc-GPS usefulness and determine its typical accuracy, we conducted a comprehensive fixed trial, (i.e. units transmitting from a single location, and obtained 40 000 locations, each associated with a known positioning error. Fastloc-GPS tags linked to the Argos system were then deployed on migrating sea turtles in the Indian Ocean and Mediterranean Sea, from which we computed simple measurements, such as heading and speed of travel over intervals of only a few hours. The fixed trials showed that the GPS accuracy was ten to hundred times better than Argos locations, with our tracking results showing the complexity of sea movements during migration. This complexity included repeated small-scale course corrections, fine-tune goal targeting, uses of the sea bed to re-set compass heading and downwind final approaches of islands suggesting the use of air-borne orientation cues. On the foraging grounds, Fastloc-GPS revealed a mosaic of discrete resting and feeding areas and complex heterogeneity in environmental use. The rich dataset provided by Fastloc-GPS opens new opportunities for understanding marine animal movements.