Update of the Loggerhead Sea Turtle (Caretta caretta) Population Nesting in Koroni, Greece, Mediterranean.

Abstract

Long-term monitoring programs are valuable in assessing population trends and evaluating conservation status especially for threatened species exhibiting delayed maturity such as marine turtles. The loggerhead sea turtle Caretta caretta is a globally distributed species with a regional population within the Mediterranean Sea. Loggerhead nesting in the Mediterranean occurs mainly in the eastern basin, with nesting areas classified as per their magnitude and density. A "moderate-dense" nesting area in Greece is the 2.7 km Koroni beach which has been monitored by ARCHELON since 1995 with the aim to collect reproductive data and to protect nests. Data collected over 25 years showed an average annual number of 55.8 nests, a nesting success (percentage of emergences resulting in egg-laying) of 38.0% and a nesting density of 20.7 nests/km. Nest numbers exhibited a significantly increasing trend in recent years, while clutch size showed a significant downward trend. Incubation durations, considered to be an indicator of incubation temperature and subsequently hatchling sex ratio, have been significantly decreasing over the years-a possible sign of global warming. A major threat is nest predation by foxes and dogs, which has been effectively controlled through the fencing of nests. This nesting population, despite its moderate size, may contribute to the genetic homogeneity of the larger western and eastern nesting aggregations of loggerhead turtles in Greece. The nesting beach has been recently included in the European Union's NATURA 2000 network of protected areas. Continuation of this long-term monitoring program is expected to provide further insights into the reproductive traits of this important loggerhead population.