Large-scale movements in the oceanic environment identify important foraging areas for loggerheads in central Mediterranean Sea
- 261 Downloads
Loggerhead sea turtles (Caretta caretta) are known to display a wide range of movement patterns during the different stages of their life cycle, but empirical information to document this extensive behavioural plasticity is still limited. This is especially true for large, adult-sized individuals, that are thought to mainly forage in neritic areas. In the present paper, eight adult-sized loggerhead turtles were tracked using satellite telemetry to identify the location of their foraging grounds in the seas along the western coast of the Italian peninsula. Tracked turtles mostly stayed in the region between the Italian peninsula and the islands of Sicily and Sardinia, that was reached following quick, directed movements by the turtles from a release site to the north. In this area, two turtles took up residence in spatially limited neritic sites along the coast, while the remaining six alternated circumscribed coastal stays with long-distance, circuitous movements in the oceanic environment. An utilization distribution analysis clearly identified an area, mostly comprising oceanic waters, that was continuously used by turtles in different seasons and years. The present results contribute to the still-limited knowledge of the spatial ecology of loggerheads frequenting the Western Mediterranean Sea and highlight the presence of a potentially important oceanic region in the Southern Tyrrhenian Sea where adult-sized turtles forage for extended periods. These findings increase our knowledge of complex life history traits of loggerhead turtles and provide important information to be considered for evidence-based conservation measures.
The authors are grateful to Mariapia Ciampa, Gianluca Treglia, Fulvio Maffucci and the staff of Punta Campanella Marine Protected Area, TartAmare and A.D. Club Subacqueo Grossetano (Grosseto) for their help in the recovery and releases of tracked turtles. Funds were obtained from SZN, University of Pisa (Progetti di Ricerca di Ateneo, Grant #PRA_2016_1) and Regione Toscana (Bando Go-Green Mare 2014). One satellite tag was purchased from a Grant to G. C. Hays from the Natural Environment Research Council of the U.K. (NERC, Grant NER/A/S/2003/00302).
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
All procedures performed in studies involving animals were in accordance with the ethical standards of the institution or practice at which the studies were conducted. Transmitter deployments were authorised by the Italian Ministry of Environment (Prot. nos. 002451/PNM, DPN-2010-0000872, 0042848/PNM 09 and DP-2009-0023740).
- Arendt MD, Segars AL, Byrd JI, Boynton J, Schwenter JA, Whitaker JD, Parker L (2012b) Migration, distribution, and diving behavior of adult male loggerhead sea turtles (Caretta caretta) following dispersal from a major breeding aggregation in the Western North Atlantic. Mar Biol 159:113–125CrossRefGoogle Scholar
- Bolten AB (2003) Active swimmers—passive drifters: the oceanic juvenile stage of loggerheads in the Atlantic System. In: Bolten AB, Witherington BE (eds) Loggerhead sea turtles. Smithsonian Institution, Washington, pp 63–78Google Scholar
- Casale P, Margaritoulis D (2010) Sea turtles in the Mediterranean: distribution, threats and conservation priorities. IUCN, GlandGoogle Scholar
- Casale P, Freggi D, Basso R, Argano R (2005) Size at male maturity, sexing methods and adult sex ratio in loggerhead turtles (Caretta caretta) from Italian waters investigated through tail measurements. Herpetol J 15:145–148Google Scholar
- Coll M, Piroddi C, Alboui C, Ben Rais Lasram F, Cheung WWL, Christensen V, Karpouzi VS, Guilhaumon F, Mouillo D, Paleczny M, Palomares ML, Steenbeek J, Trujillo P, Watson R, Pauly D (2012) The Mediterranean Sea under siege: spatial overlap between marine biodiversity, cumulative threats and marine reserves. Global Ecol Biogeogr 21:465–480CrossRefGoogle Scholar
- Ehrhart LM, Ogren LH (1999) Studies in foraging habitats: capturing and handling turtles. In: Eckert KL, Bjorndal KA, Abreu-Grobois FA, Donnelly M (eds) Research and management techniques for the conservation of sea turtles. IUCN/SSC Marine Turtle Specialist Group Publication 4, pp 1–4Google Scholar
- Fiori C, Paolo C, Alessi J, Mandich A, Vassallo P (2016) Seamount attractiveness to top predators in the southern Tyrrhenian Sea (central Mediterranean). J Mar Biol Assoc UK 96:769–775Google Scholar
- Fossette S, Witt MJ, Miller P, Nalovic MA, Albareda D, Almeida AP, Broderick AC, Chacon-Chaverri D, Coyne MS, Domingo A, Eckert S, Evans D, Fallabrino A, Ferraroli S, Formia A, Giffoni B, Hays GC, Hughes G, Kelle L, Leslie A, Lopez-Mendilaharsu M, Luschi P, Prosdocimi L, Rodriguez-Heredia S, Turny A, Vehage S, Godley BJ (2014) Pan-Atlantic analysis of the overlap of a highly migratory species, the leatherback turtle, with pelagic longline fisheries. Proc R Soc Lond B 281:20133065CrossRefGoogle Scholar
- Hatase H, Takai N, Matsuzawa Y, Sakamoto W, Omuta K, Goto K, Arai N, Fujiwara T (2002) Size-related differences in feeding habitat use of adult female loggerheads Caretta caretta around Japan determined by stable isotope analyses and satellite telemetry. Mar Ecol Prog Ser 233:273–281CrossRefGoogle Scholar
- Kobayashi DR, Polovina JJ, Parker D, Kamezaki N, Cheng IJ, Uchida I, Dutton PH, Balazs GH (2008) Pelagic habitat characterization of loggerhead sea turtles, Caretta caretta, in the North Pacific Ocean (1997–2006): insight from satellite tag tracking and remotely sensed data. J Exp Mar Biol Ecol 356:96–114CrossRefGoogle Scholar
- Margaritoulis D, Argano R, Baran I, Bentivegna F, Bradai MN, Caminas JA, Casale P, De Metrio G, Demetropoulos A, Gerosa G, Godley BJ, Haddoud DA, Houghton J, Laurent L, Lazar B (2003) Loggerhead turtles in Mediterranean Sea: present knowledge and conservation perspectives. In: Bolten AB, Witherington BE (eds) Loggerhead sea turtles. Smithsonian Books, Washington, pp 175–198Google Scholar
- Mencacci R, Ligas A, Meschini P, Luschi P (2011) Movements of three loggerhead sea turtles in Tuscany waters. Atti Soc Tosc Sci Nat Mem Serie B 118:117–120Google Scholar
- Musick JA, Limpus CJ (1997) Habitat utilization and migration in juvenile sea turtles. In: Lutz PL, Musick JA (eds) The biology of sea turtles. CRC Press, Boca Raton, pp 137–164Google Scholar
- Pikesley SK, Broderick AC, Cejudo D, Coyne MS, Godfrey MH, Godley BJ, Lopez P, Lopez-Jurado L-F, Merino SE, Varo-Cruz N, Witt MJ, Hawkes LA (2015) Modelling the niche for a marine vertebrate: a case study incorporating behavioural plasticity, proximate threats and climate change. Ecography 38:803–812CrossRefGoogle Scholar
- R Core Team (2017) R: a language and environment for statistical computing. R Foundation for Statistical Computing, AustriaGoogle Scholar
- Rovere M, Bo M, Alessi J, Paoli C, Villani N, Vassallo P, Fiori C, Roccatagliata N (2015) Seamounts and seamount-like structures of the Tyrrhenian Sea. In: Würtz M, Rovere M (eds) Atlas of the Mediterranean Seamounts and seamount-like structures. IUCN, Gland, pp 111–186Google Scholar
- Schofield G, Dimadi A, Fossette S, Katselidis KA, Koutsoubas D, Lilley MKS, Luckman A, Pantis JD, Karagouni AD, Hays GC (2013) Satellite tracking large numbers of individuals to infer population level dispersal and core areas for the protection of an endangered species. Divers Distrib 19:834–844CrossRefGoogle Scholar
- Seaman DE, Powell RA (1990) Identifying patterns and intensity of home range use. Int Conf Bear Res Manage 8:243–249Google Scholar