• Caretta caretta
• Chelonia mydas
• diving behavior
• gps
• iridum system
• migration
• satellite tracking
• sea turtles

Wildlife tracking allows researchers to have a deep look on the ecology and ethology of various species; one of the most useful tools to study the animals’ spatial behavior is satellite tracking.
The most widespread system used to this aim is the ARGOS one, but recently another satellite network has been proposed as an alternative tracking method: the IRIDIUM system.
IRIDIUM consists in a constellation of 66 LEO satellites that provides global coverage and a 2-way communication with devices deployed on the animals. Through IRIDIUM, we can obtain localizations acquired through GPS receivers and even data from various sensors onboard the tag, like diving data.
My study aims to evaluate the performances of IRIDIUM-GPS transmitters to track adult sea turtles during their movements and to remotely obtain information on their diving behavior. To this aim, data from 5 female loggerhead turtles (Caretta caretta), tracked from Itzuzu beach, near Dalyan, Turkey, and 3 female green turtles (Chelonia mydas), tracked from Aldabra Atoll, Seychelles, were collected. All individuals were equipped with an IRIDIUM-GPS tag and followed during the inter-nesting phase, the post-nesting migration and the foraging phase. The devices collected both GPS localizations and sensor data from which the turtle diving activity could be assessed (i.e. the percentage of time spent underwater, UW%, and the average duration of each dive, ADD). These data were then organized, filtered and analyzed in order to evaluate the performance of IRIDIUM.
Turtles were followed for a period that ranges from 80 d to 886 d. During this period, the 15-40% of the expected GPS data and the 50-95% of the expected diving data were acquired, with important differences between the two populations and among the three phases in both species, probably due to different behaviors of tracked turtles. The amount of data relayed to the satellites are satisfactory, especially for the diving data; in loggerhead turtles, for example, we obtained over the 90% of the expected ones. For the GPS localizations, the average daily number of fixes obtained ranged between 8-14 fixes/d.
From the localizations obtained, it was possible to reconstruct the migratory routes in most, but not all, cases. Most turtles displayed a typical migratory behavior, displaying the typical three phases, i.e. the inter-nesting, the post-nesting migration from the nesting site towards the feeding area, and the foraging phase, in which the turtle resides in an individually-specific area until the following reproductive season. One of the loggerheads, however, showed a very different behavior, sometimes observed in this species, consisting in remaining for long time in offshore waters and frequenting disparate areas of the Aegean Sea, of central Mediterranean Sea, before reaching the Ionian and the Adriatic Sea, where it remained for months. Moreover, the analysis of the UW% and the ADD confirmed that sea turtles performed longer dives during the inter-nesting and the foraging phase and shorter ones during the post-nesting migration.