Behavioural plasticity in the use of a neritic foraging area by loggerhead sea turtles: insights from 37 years of capture-mark-recapture in the Adriatic Sea (Mediterranean Sea)

Assessing sea turtle movements and connectivity among different areas is pivotal to understanding their biology and implementing efficient conservation actions. In the Adriatic Sea, one of the most important sea turtle foraging areas in the Mediterranean, a total of 311 capture-mark-recapture (CMR) records (mostly bycatch) from 294 loggerhead turtles (Caretta caretta) in the period 1984-2021 were analysed. A general fidelity pattern to Adriatic subareas was indicated by a significantly shorter CMR distance than the potential dispersal distance and by the significantly higher proportion of re-encounters in the same area of release than expected. No seasonal pattern was detected between subareas, and shorter re-encounter distances were observed in turtles released and re-encountered in the same season, suggesting different winter and summer residential areas. Results suggest that turtles frequenting the Adriatic can go anywhere in the Mediterranean basin and may exhibit a wandering behaviour regardless of their size. A substantial connectivity with nesting sites in Greece was observed, confirming with empirical evidence that this is the most important breeding area for turtles foraging in the Adriatic Sea. This study highlights the value of cooperation among different groups and shows a main behavioural pattern of fidelity to neritic foraging grounds.