Sea Turtles in Kefalonia

Sea Turtles in Kefalonia, Greece

The Loggerhead sea turtle, Caretta caretta nests on most of the southern sandy beaches of Kefalonia. Many of these beaches have been untouched by human development until recently, and therefore offered turtles a safe place to nest, secluded from the outside world. However, in the past 30 years tourist development has been encroaching into some of these untouched nesting habitats.

We monitor the population of Loggerhead sea turtles on the main nesting site of Kefalonia; Mounda beach. This beach has been monitored every year for more than 25 years by different projects. The number of nests here has shown signs of decline in the last decade. We are also making an effort to monitor other nesting beaches, to assess the general situation of the island population.

Loggerhead sea turtles in Kefalonia are very similar to their fellows in the Mediterranean, which in turn are little different from oceanic Loggerheads, mostly in that they are smaller. A brief list of their features (all figures are approximations of averages) – adult female length: 1 m – hatchling at birth length: 5 cm – adult female weight: up to 100 kg – hatchling at birth weight: less than 20 g – sexual maturity minimum age: probably 20 years – number of eggs in a nest: 100-110 – proportion of infertile eggs in each nest: 5-20% – number of nests laid in a season by one turtle: 2-3 – years between nesting for a turtle: 2-3 – nesting season: end of May – beginning of August – hatchling season: end of July – beginning of October – incubation period: 55 days – nest depth: 20-50 cm   Kefalonian Loggerhead sea turtles are remarkable in various ways. The island is one of the northernmost nesting sites of sea turtles in the world. This might have important implications in the sex ratio of offspring produced on the island. Temperatures during incubation determine the sex of sea turtles, in a process called Temperature-dependant Sex Determination. Higher temperatures produce more females. Many studies agree on assigning a female skewness to Mediterranean sea turtle populations.

Therefore, nesting sites with lower temperatures produce more males and can be considered male reserves. They acquire even further importance in view of global warming. It makes sense to hypothesize that the latitude of Kefalonia produces lower temperatures on its nesting beaches and therefore more males, although this has not been investigated.   Kefalonia is also unique in hosting a resident population of Loggerhead sea turtles. There is evidence that a small population of turtles spend the winter in Koutavos lagoon near Argostoli. This is an exception for a highly migratory group like sea turtles and Caretta caretta specifically.