Hello, I’m Amandine and I just finished my eight week internship with Wildlife Sense in Kefalonia. I’m a French student at the engineering school VetAgro Sup and I did this internship as part of my animal behaviour’s studies. During this period, I conducted research at the Argostoli Harbour regarding the foraging behaviour of sea turtles. I chose Wildlife Sense because research is an important part of Wildlife Sense’s work and it gave me the opportunity to lead a research project.
Foraging behaviour of loggerhead turtles in Kefalonia has in the past been studied in a natural environment and the preferred food sources were bivalves, sea grass and entrails of fish (Hougthon et al. 2000). The purpose of my project was to understand what the turtles’ diets mainly consisted of in the harbour and if people who fed them increased the social antagonistic interactions between them. The harbour is an environment less natural than that studied by Houghton et al. 2000. In the harbour we observed several anthropogenic activities, such as fishermen selling their fish and many tourists interacting with the sea turtles.
During daily morning surveys (7:30 am to 1:00 pm), myself and trained Wildlife Sense volunteers collected data in the harbour. They recorded all observations on my data sheet. When a turtle was observed feeding, the gender of the turtle was recorded, along with what food they were eating (bivalve, fish, sea grass, human refuse or other), the origin of food (wall, fisherman, tourist or other) and if there was an interaction with other turtles during the feeding event. When an interaction occurred after a feeding event, it was categorized as a head to tail circle, chasing, biting or sparring.
During the last two months more than 800 foraging behaviours were reported. My preliminary results show that in the harbour females ate just as many fish as they ate bivalves, while males ate more fish. Only 125 foraging events are followed by an interaction with another harbour sea turtle. I found there were more interactions when turtles ate fish and the type of interaction that was observed most was biting. When turtles were seen eating bivalves, we observed more chasing than biting interactions. But the kind of food and its origin was found not to have a significant impact on the type of interaction according to my statistical analysis.
In the harbour, there are fishing boats present every day, which can explain why the harbour turtles eat a lot of fish. Indeed, local fishermen throw away fish and entrails of fish. As stated previously, females ate as many fish as bivalves, one explanation for this behaviour is that they need calcium for their eggs to develop during the nesting season, while males do not.
People who fed turtles in the harbour seemed to increase the social antagonistic interaction between them, because we observed more interactions when the turtles were feeding on fish. Turtles were found to be more aggressive when they ate fish rather than when they were feeding on bivalves because the intensity of the interaction following the foraging event differed. Indeed, we observed more biting after they fed on fish, which is a more intense interaction, according to Schofield et al. (2006), than chasing which often followed a feeding event on bivalves. This leads me to believe there is more competition for the fish than bivalves, most likely because bivalves can be found all along the harbour wall, while the few fishing boats that are present are the only realistic source of fish for sea turtles. It is commonly misconceived that sea turtles’ diets mainly consists of fish, however in reality this is impossible because they are not fast enough to catch many types fish (White 2004).
Although I have left the island, this data will continue to be collected every morning until the end of the season. I really enjoyed my time in Kefalonia and I want to thank Chanel and Nikos for all the knowledge they have given me and all Wildlife Sense volunteers who helped me to conduct my research project. It was an amazing experience to be part of the Wildlife Sense team during these past two months!