Movements and diving behaviour of inter-nesting leatherback turtles in an oceanographically dynamic habitat in South Africa

Sea turtles congregate in specific in-water habitats during reproductive periods. These habitats are inherently tied to the location of their nesting beaches, but they are also influenced by the prevailing oceanographic conditions. Here, we characterized the movements and diving behaviour of leatherback turtles Dermochelys coriacea between nesting events at the iSimangaliso Wetland Park, South Africa. Furthermore, we characterized the general oceanographic features (sea surface temperature and ocean currents) in and around the identified internesting habitats. To achieve this, we deployed satellite transmitters onto 10 inter-nesting leatherback turtles. Many of these turtles were tracked over multiple inter-nesting intervals; in total, we collected data over 25 inter-nesting intervals. Inter-nesting turtles generally stayed within 100 km of the coastline, but they moved large distances north and south, covering approximately 600 km of the coast. Even though sea surface temperatures increased notably over the nesting season, we did not observe any obvious change in the movement or diving patterns of leatherback turtles tracked over consecutive inter-nesting intervals, suggesting that turtles were not selecting internesting habitats based on local sea surface temperature patterns. However, we propose that the fast-flowing Agulhas Current may provide a natural boundary for the movements of inter-nesting turtles. We hypothesize that inter-nesting turtles might be avoiding fast flowing waters to minimize energy expenditure or avoid being advected away from the nesting habitats.