Hi, I am Coralie and I am currently doing a Masters degree in Marine Biology at the University of Pierre et Marie Curie (Paris VI). Last summer I carried out an internship for 4 weeks with Wildlife Sense. I conducted a preliminary study on light pollution and sand characteristics on nesting beaches in order to compare loggerhead sea turtles’ and humans’ favorite beaches.
Sea turtles need specific environmental conditions to nest and obtain a good hatching success. Among them, sand characteristics, like moisture and grain size, are very important. Sea turtles lay their eggs in the moist intermediate layer into the sand where Ackerman (1997) estimated the water content to be around 4-6%. Regarding the texture of the sand, turtles would not like very coarse or very fine sand that makes digging too hard and induce often the abandonment of the egg chamber. Thus, loggerhead sea turtles generally nest on beaches with medium-sized sand grains, between 0.25 and 0.5 mm.
Therefore, we desired to evaluate what were the characteristics of Kefalonian nesting beaches and if they were correlated with the ones found in the literature. I took random samples of around 250 g of sand on every nesting beach which we surveyed, with the aim of determining their sand characteristics. For that, I dug turtle-like holes of 30 cm deep where I took my samples, as it corresponds to the average mid-nest depth in Kefalonia. Then, we dried the sand samples by cooking them and weight them again to deduce the percentage of moisture. After that, we sieved the samples using a stack of scientific sieves to separate the different grain size classes and see which one was dominant. Finally, we wanted to analyze if there were correlations between the percentage of moisture and the grain size with the favorite nesting beaches.
Humans’ activity on littorals and tourism induce an increasing light pollution near sea turtle nesting beaches which is a serious issue for this endangered species. First of all, artificial lighting may deter adults. In fact, they can be scared more easily by shades or movements on the beach and may turn back to the sea without nesting. They even may not emerge thinking that it is always daytime, so not the time to nest. Second, these lights can disrupt hatchlings which would be disoriented or misoriented. Consequently, they would not be able to find the sea and may die by dehydration and/or exhaustion.
In order to estimate light pollution on our nesting beaches, we used a light meter to measure light intensity on each beach after the sunset. Then, we determined if the identified light source was artificial, like street lights or beach bars, to distinguish it from the moonlight. Moonlight is a natural source and does not constitute an issue because it is less bright and has a wide distribution contrary to artificial lighting which is very bright and directed in a specific spot. Nights with full moon are even better for sea turtles because it lowers light pollution from artificial lights, unlike nights without moon which are the most dangerous.
My time at the project was not enough to make statistically significant conclusions. However, light pollution surveys and sand sampling continued after my departure during the whole nesting season and will be done again during the following years. Moreover, other important parameters as sand temperature affects the survival and becoming of newborns and should be measured in order to obtain a more complete view of the nesting context. The collection of all these data will allow to have a better idea of the situation and, consequently, be able to estimate and organize the best management that can be expected.
During my four weeks there, I also practiced every day the voluntary work. I participated to morning surveys to look for turtle tracks and nests on nesting beaches. I also helped for the relocation of several nests which were too close to the sea, threatening the eggs. Some surveys were also dedicated to the study of the foraging and social behavior of the turtles present in the harbor of Argostoli. Thanks to these observations, turtles hurt by hooks or entangled into fishing line were sometimes seen and could be helped by the intervention of the Wildlife Sense team.
I would like to thank very much Nikos and Chanel for having allowed me to live this experience and shared their knowledge with me. As well as acquiring a new experience as part of my studies, I met wonderful people with who I spent an amazing month. I hope to have the possibility to repeat this adventure next year !