Species description and status: The Loggerhead turtle is a migratory species with a worldwide distribution across subtropical and temperate regions of the Mediterranean Sea and Pacific, Indian, and Atlantic Oceans1 (Figure 1). Loggerhead turtles, mostly tied to their natal beach for reproduction, have a complex life cycle with a succession of developmental stages that passes from oceanic habitats to neritic areas where large juveniles recruit and grow to adult size. The Mediterranean subpopulation breeds along the coasts of the eastern Mediterranean basin (with just a few individual nests recorded in the western basin) and its marine habitats extend throughout all the Mediterranean2. The European Atlantic coasts are also frequented by juveniles originating from West Atlantic and West African rookeries, some of which enter the Mediterranean through the Strait of Gibraltar. During the last IUCN Red List assessment the NW Atlantic and the Mediterranean subpopulations were both assess as “least concern” albeit strongly conservation dependent, since the main threats including fisheries by-catch, habitat degradation and pollution still persist. (Image above by Sandra Hochscheid ©)
Figure 1. Global distribution and nesting sites for the loggerhead turtles Caretta caretta (from Wallace et al. 2010)
Knowledge gaps: Research gaps which can be filled with telemetry studies have been identified by the Demographic Working Group of the 5th Mediterranean Conference on Marine Turtles3 and by a recent review by Mediterranean sea turtle experts2. Priorities concern movement patterns of juvenile turtles, and adult turtles from key rookeries, as well as identifying dispersal patterns of post-hatchlings and small juveniles and if climate change might impact geographical range.
Regions of interest: Loggerhead turtles are widely distributed in European waters, but more so in the Mediterranean. Developmental habitats in the Adriatic Sea and Western Mediterranean are of interest as well as migration routes to and from major rookeries in Greece, and smaller new nesting sites in Italy and Spain.
Telemetry tools: The most widely applied telemetry method is satellite tracking, which has been employed successfully on adult and juveniles turtle and recently even to small (> 13 cm standard carapace length) captive reared individuals. Satellite tags equipped with other sensors that can collect behavioural and environmental data together with GPS quality locations are preferred, because of their potential to deliver biological information important for the management of the species. Acoustic telemetry can also be used to track this species movements.
Benefits within ETN: Using the ETN to further characterize loggerhead turtle movements and behaviour throughout Europe would greatly enhance our ability to better inform decision makers and conservation managers to adopt specific measures of protection of this species. In addition, ETN would give necessary insights in habitat use and possible range expansions due to climate warming.
Previous and current projects on loggerhead turtles: LIFE EUROTURTLES and LIFE MEDTURTLES, a geographical extension of the former, aiming to improve the conservation status of the EU populations of the Habitats Directive priority sea turtle species Caretta caretta and Chelonia mydas.
1 Wallace, B. P., DiMatteo, A. D., Hurley, B. J., Finkbeiner, E. M., Bolten, A. B., Chaloupka, M. Y., Hutchinson, B. J., Abreu-Grobois, F. A., Amorocho, D. F., Bjorndal, K. A., et al. (2010) Regional management units for marine turtles: a novel framework for prioritizing conservation and research across multiple scales. PLoS ONE 5, e15465.
2 Casale, P., Broderick, A. C., Caminas, J. A., Cardona, L., Carreras, C., Demetropoulos, A., Fuller, W. J., Godley, B. J., Hochscheid, S., Kaska, Y., et al. (2018) Mediterranean sea turtles: current knowledge and priorities for conservation and research. Endangered Species Research 36, 229-267.
3 Cardona L., A. Broderick, J.A. Caminas, P. Casale, W.J. Fuller, B. Godley, S. Hochscheid, Y. Kaska, B. Lazar, Y. Levy, F. Maffucci, C. Miaud, C. Misfud, & J. Tomas (2015) Demography of marine turtles nesting in the Mediterranean Sea: a gap analysis and research priorities. 35th meeting, Convention on the Conservation of European Wildlife and Natural Habitats, Standing Committee, Strasbourg, 1-4 December 2015, T-PVS/Inf(2015)15E