NESTING SITE FIDELITY IN LOGGERHEAD SEA TURTLES
Caretta caretta ON THE GREEK ISLAND OF KEFALONIA
Michael G. White
Pen-Y-LÛ n, Mynydd Eilian, Ynys MÛ n
LL68 9NN, Wales
Four different aspects of nesting site fidelity were considered for loggerhead sea turtles Caretta caretta, which nested on the Greek Island of Kefalonia in 1998. The frequency and timing of remigration was determined for a 14-year period 1985-1998. Intra-beach spatial fidelity and the inter-nesting period was recorded and compared with data from previous years. VHF radio telemetry was used to investigate inter-nesting habitat use and the diving patterns of three turtles. Track patterns at Mounda Beach were measured in an attempt to identify fixed characteristics unique to an individual turtle. Possible instances of site infidelity were identified from nesting and emergence activity on secondary beaches. A detailed study was made of the life history and nesting success of all 15 turtles that nested at the Mounda Beach rookery during 1998. Although more than 60% of tagged animals are never seen again, the turtles that do return to this site do so regularly. Resident turtles contribute 75% of the total reproductive output at this site. Mounda Beach is biologically important because of low predation levels, a high encounter rate (100%) with nesting adults, and intermittent hatchling emergence. The need to limit building development at Mounda Beach to a sustainable level is supported by this study, in conjunction with reports from the Kefalonian Marine Turtle Project. The elevated ambient air and substrate temperatures in 1998 were the possible cause of a reduced incubation period for a number of nests, the shortest being 47 days; as well as an increased level of neonate mortality and egg-death rates, compared with previous years. One loggerhead could have laid a nest at another site, as there was a 38-day interval between nests at Mounda.