Loggerhead turtles on Kefalonia

LOGGERHEAD TURTLES

Sea turtles date back to the time of dinosaurs, evolving into something resembling their present features around 60,000,000 years ago. Two species inhabit the seas around Greece, the Loggerhead turtle (Caretta caretta), so named due to its large head, and the Green turtle (Chelonia mydas), named after its distinctive green colouring.

The Loggerhead, distinguished by its big head, a reddish-brown shell and yellow/brown skin, is one of the oldest species in the world.

An adult Loggerhead grows to a length of 1.1-1.2 m, weighs between 100-385 kg and can live for around 65 years. Although many don’t make it to this age, some may reach much older. Average adults in the Mediterranean tend to be slightly smaller than average adults in the Atlantic. Toothless, their powerful jaws are capable of crushing molluscs and crustaceans and they also feed on jellyfish, fish, the Portuguese Man o’ War and other small- to medium-sized marine creatures. Watch a brief but fascinating video clip of a Loggerhead catching and consuming a crab.

Two sub-species of Loggerhead are generally recognised: Caretta caretta gigas, found in the Indian and Pacific Oceans, and C. caretta carreta, the Atlantic Loggerhead. The largest collections of Atlantic Loggerhead turtle nesting grounds are on the east coast of America, from Texas to North Carolina. They also nest on beaches on Brazil and West Africa and the Mediterranean, where. Zakynthos is one of the largest sites. There are also nest sites at Dalyan, south-western Turkey, the Greek island of Kefalonia, Akamas and Alagadi beaches on Cyprus and the Italian islands of Lampedusa and Linosa.

On Kefalonia the principal nesting site is below Ratzakli at Mounda Bay, between Skala and Katelios.

The Loggerhead makes the longest migration journeys of any sea turtles and may be unique among sea turtles in that mating occurs anywhere between the feeding grounds and nesting beaches, rather than only near to the nest sites.

As male turtles never return to land after hatching little is known about their whereabouts or habits, it is invariably female turtles that are tagged and from which information about migration paths is gathered.

Generally, the Atlantic Loggerhead follows a gyratory migration path. According to Peter Richardson of the Marine Conservation Society, Loggerheads travel around the North Atlantic ocean currents in a wide loop. From nesting beaches in Florida, they follow the Gulf Stream across the Atlantic to Madeira, and then head south to the Canary Islands and Cape Verde Isles, before heading back to the south-east coast of the US.

From what is known, it seems Loggerheads reach sexual maturity between ten to thirty years from birth. Mating occurs between late March and early June and female turtles return at night, often but not always, to the beach they were born to lay their eggs, typically between 70 – 150/200 eggs in one nest. The eggs, which are round and approximately the size of table-tennis balls, are laid in a chamber hollowed between 40 – 60 cm (1’ 4” - 2’) deep in the sand and covered with sand after laying. The female turtles can repeat this process after some 15 days and may nest three or four times a season, mating several times between nesting.

Incubation lasts for approximately sixty days and the sex of the hatchlings is determined by the egg temperature during the middle period of incubation. Generally, the pivotal temperature, where a clutch produces 50% male and 50% female hatchlings, is between 28° C - 30° C. Temperatures between 24° C - 26° C produce mostly males, between 32° C - 34° C mostly females. Outside these temperatures it's doubtful the eggs will hatch. The actual period of incubation depends upon the temperature within the nest, this can be affected by the weather, shade, heat generated within the nest and each individual egg's position in the nest. At the lower survivable temperatures, incubation may take 65-70 days; at the higher range, incubation may take only 45 days.

Newly hatched turtles mostly emerge at night, when risk from predators is lower, and are attracted by the light of the moon, and gravity, into the sea. Lights from tavernas, bars, hotels, etc, can disorientate the new-born turtles and attract them away from the sea. Obstructions on the beach are also detrimental to hatchlings reaching the sea. Hatchlings need the journey to the sea to build up their strength and ‘helping’ them into the sea by picking them up and carrying them may reduce their chances of survival in the sea.

Unable to retract in to their shells, as tortoises and terrapins can, turtles rely on their hard shell and leathery skin for protection. Natural predators include sharks.

At sea, turtles may fall foul of fishing nets, lines and contact with boats. These are real threats and can happen any-where: only female turtles come ashore and predominantly at night, when few small, fast boats are at sea. In Australia is has been predicted that the annual survival rate is 92% for immature turtles and 88% for adults.

The study of sea turtles on Kefalonia was conducted by the Marine Turtle Research Project from 1984 to 1995. The Kefalonian Marine Turtle Project operated between 1996 – 1998 with the aims of conducting a short-term biological assessment of the rookery, identifying the major threats to the population and encouraging the establishment of a local conservation group which would remain active after the short term goals were achieved. Working closely with the surrounding communities, a local initiative led to the formation of the Katelios Group for the Research and Protection of Marine and Terrestrial Life in 1996.

At this time the Katelios Group consisted of members of the local community, many of whom were involved in or connected with fishing, who worked positively to sensitise the community to the issues of turtle conservation.

Today the Katelios Group seems to effectively consist of only one (somewhat 'eccentric') local person, the rest consist of an imported team leader (presumably paid, no accounts published) and an ever-changing collection of youthful volunteers who tend to arrive full of enthusiasm only to become disillusioned with the running of the group. Regretably, the group has alienated 99% of the local population.

Most nesting sites in Greece are co-ordinated by Archelon, here's a short video showing the major nesting sites.

The best place to see Loggerheads on Kefalonia is Argostoli.

Although the females nest on Mounda Bay and a few other beaches, it's mostly early season and at night (so it's dark and difficult to see them) and we don't want them to be disturbed. Head down to the seafront in Argostoli when the fishing boats are there selling their catch, e.g. between about 08:00 – 14:00, Monday to Saturday, and there's a very good chance one or more will be swimming around waiting for their free lunch. Early evening is also a good time to see them.