Life cycle and ecology of the loggerhead turtle (Caretta caretta, Linnaeus, 1758): development and application of the Dynamic Energy Budget model

Abstract

Short layman summary: Question driving my research was "What are the effects of plastic ingestion on loggerhead turtle's biology and ecology?". The overall aim was to provide new insights into processes important for the life cycle and ecology (growth, maturation, and reproduction) of this protected migratory species. Using the collected experimental and literature data, I developed a model based on the Dynamic Energy Budget theory that spans the full life cycle of the turtle. The model was then used to compare North Atlantic and Mediterranean populations, and to study the environmental (food density and temperature) and anthropogenic (plastic pollution) pressures on loggerhead turtles. Some of the results were surprising. I could explain from the differences in parameter values between both populations, why North Atlantic individuals that visit the Mediterranean See cannot reproduce there. The local population manages to do so by adaptation to the low level of food availability in this sea: they mature at a smaller size. This shows that this species lives at the edge of its capabilities, which also became visible in another more shocking way: the consumption of plastic lowers food intake. If plastic occupies only 3% of the storage-gut capacity, this has already major effects on the ultimate size they can obtain and dramatically reduces reproductive output. Such volumes are already encountered in practice, highlighting the importance of responsible management of waste