Scientia Marina, Vol 71, No 2 (2007)

Survival probabilities of loggerhead sea turtles (Caretta caretta) estimated from capture-mark-recapture data in the Mediterranean Sea

Paolo Casale
Dipartimento di Biologia Animale e dell’Uomo, Università “La Sapienza”, Roma , Italy

Antonios D. Mazaris
Biodiversity Conservation Laboratory, Department of Environmental Studies, University of the Aegean, Mitilene , Greece

Daniela Freggi
Sea Turtle Rescue Centre WWF Italy , Italy

Roberto Basso
Museo Civico di Storia Naturale di Jesolo , Italy

Roberto Argano
Dipartimento di Biologia Animale e dell’Uomo, Università “La Sapienza”, Roma , Italy


Survival probabilities of loggerhead sea turtles (Caretta caretta) are estimated for the first time in the Mediterranean by analysing 3254 tagging and 134 re-encounter data from this region. Most of these turtles were juveniles found at sea. Re-encounters were live resightings and dead recoveries and data were analysed with Barker’s model, a modified version of the Cormack-Jolly-Seber model which can combine recapture, live resighting and dead recovery data. An annual survival probability of 0.73 (CI 95% = 0.67-0.78; n=3254) was obtained, and should be considered as a conservative estimate due to an unknown, though not negligible, tag loss rate. This study makes a preliminary estimate of the survival probabilities of in-water developmental stages for the Mediterranean population of endangered loggerhead sea turtles and provides the first insights into the magnitude of the suspected human-induced mortality in the region. The model used here for the first time on sea turtles could be used to obtain survival estimates from other data sets with few or no true recaptures but with other types of re-encounter data, which are a common output of tagging programmes involving these wide-ranging animals.


loggerhead sea turtle; survival; capture-mark-recapture; Mediterranean; Barker’s model

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Argano, R. – 1992. Sea turtles and monk seal in Italian seas: conservation and perspectives. Boll. Mus. Ist. Biol. Univ. Genova, 56-57: 113-135.

Barker, R.J. – 1997. Joint modeling of live-recapture, tag-resight, and tag-recovery data. Biometrics, 53: 666-677. doi:10.2307/2533966

Barker, R.J. – 1999. Joint analysis of mark recapture, resighting and ring-recovery data with age-dependence and marking-effect. Bird. Study, 46: 82-90.

Barker, R.J., K.P. Burnham and G.C. White. – 2004. Encounter history modeling of joint mark-recapture, tag-resighting and tagrecovery data under temporary emigration. Stat. Sinica, 14: 1037-1055.

Barker, R.J. and G.C. White. – 2001. Joint analysis of live and dead encounters of marked animals. In: R. Field, R.J. Warren, H. Okarma and P.R. Sievert (eds.), Wildlife, Land, and People: Priorities for the 21st Century, Proc. 2nd Int. Wildl. Manag. Cong. The Wildlife Society, Bethesda, Maryland, USA, pp. 361-367.

Bjorndal, K.A., A.B. Bolten and M.Y.Chaloupka. – 2003a. Survival probability estimates for immature green turtles Chelonia mydas in the Bahamas. Mar. Ecol. Prog. Ser., 252: 273-281. doi:10.3354/meps252273

Bjorndal, K.A., A.B. Bolten and H.R. Martins. – 2003b. Estimates of survival probabilities for oceanic-stage loggerhead sea turtles (Caretta caretta) in the North Atlantic. Fish. Bull., 101: 732-736.

Bolten, A.B. – 1999. Techniques for measuring sea turtles. In: K.L. Eckert, K.A. Bjorndal, F.A. Abreu-Grobois and M. Donnelly (eds.), Research and Management Techniques for the Conservation of Sea Turtles. IUCN/SSC Mar Turtle Spec Group Publication 4, pp. 110-114.

Burnham, K.P. – 1993. A theory for combined analysis of ring recovery and recapture data. In: J.D. Lebreton and P.M. North (eds.), Marked individuals in the study of bird population, pp. 199-213, Birkhauser Verlag, Basel, Switzerland.

Bowen, B., J.C. Avise, J.I. Richardson, A.B. Meylan, D. Margaritoulis and S.R. Hopkins-Murphy. – 1993. Population structure of loggerhead turtles (Caretta caretta) in the northwestern Atlantic Ocean and Mediterranean Sea. Conserv. Biol., 7: 834-844. doi:10.1046/j.1523-1739.1993.740834.x

Casale, P., Laurent, L. and G. De Metrio. – 2004. Incidental capture of marine turtles by the Italian trawl fishery in the north Adriatic Sea. Biol. Conserv., 119(3): 287-295. doi:10.1016/j.biocon.2003.11.013

Casale, P., D. Freggi, R. Basso and R. Argano. – 2005. Size at male puberty, sexing methods, and adult sex ratio in loggerhead turtles (Caretta caretta) from Italian waters investigated through tail measurements. Herp. J., 15: 145-148.

Casale, P., N. Zizzo, M. Affronte, D. Freggi, R. Basso, C. Vallini, V. Prunella, R. Argano and M. Rocco. – (in press). Evidence of human-induced mortality among turtles stranded along Italian coasts. Proc. 25th Ann. Symp. Sea Turtle Biol. Conserv.

Chaloupka, M. – 2003. Stochastic simulation modelling of loggerhead population dynamics given exposure to competing mortality risks in the Western South Pacific. In: A.B. Bolten and B. Witherington (eds.), Loggerhead Sea Turtles, pp. 274-294, Smithsonian Institution Press, Washington, DC, USA.

Chaloupka, M. and C. Limpus. – 1997. Heuristic simulation modelling of trawl fishery impacts on sGBR loggerhead population dynamics. In: S.P. Epperly and J. Braun (comps.), Proc. 17th Ann. Symp. Sea Turtle Biol. Conserv. NOAA Technical Memorandum NMFS-SEFSC-415, pp. 26-29.

Chaloupka, M.Y. and C.J. Limpus. – 2002. Survival probability estimates for the endangered loggerhead sea turtle resident in southern Great Barrier Reef waters. Mar. Biol., 140: 267-277. doi:10.1007/s002270100697

Chaloupka, M.Y. and C.J. Limpus. – 2005. Estimates of sex- and age-class-specific probabilities for a southern Great Barrier Reef green turtle population. Mar. Biol., 146: 1251-1261. doi:10.1007/s00227-004-1512-6

Chaloupka, M.Y. and J.A. Musick. – 1997. Age, growth and population dynamics. In: P.L. Lutz and J.A. Musick (eds.), The biology of sea turtles, pp. 233-275, CRC Press, LLC.

Cooch, E. and G. White. – 2002. Using MARK—A gentle introduction. Electronic Book.

Cormack, R.M. – 1964. Estimates of survival from the sighting of marked animals. Biometrika, 51: 429-438.

Dodd, C.K. Jr. – 1988. Synopsis of the biological data on the loggerhead sea turtle Caretta caretta (Linnaeus 1758). U.S. Fish Wildl. Serv., Biol. Rep. 88(14).

Epperly, S.P., M.L. Snover, J. Braun-McNeill, W.N. Witzell, C.A. Brown, L.A. Csuzdi, W.G. Teas, L.B. Crowder and R.A. Myers. – 2001. Stock assessment of loggerhead sea turtles of the western North Atlantic. NOAA Tech. Memo. NMFSSEFSC- 455.

Frazer, N.B. – 1983. Demography and life history evolution of the Atlantic loggerhead sea turtle, Caretta caretta. PhD Dissertation, University of Georgia, Athens, Georgia USA.

Frazer, N.B. – 1987. Preliminary estimates of survivorship for wild juvenile loggerhead sea turtles (Caretta caretta). J. Herp., 2: 232-235. doi:10.2307/1564489

Frederiksen, M and T. Bregnballe. – 2000. Evidence for densitydependent survival in adult cormorants from a combined analysis of recoveries and resightings. J. Anim. Ecol., 69: 737-752. doi:10.1046/j.1365-2656.2000.00435.x

Gerosa, G. and P. Casale. – 1999. Interaction of Marine Turtles with Fisheries in the Mediterranean. UNEP-MAP-RAC/SPA, Tunis.

Heppell, S.S., C.J. Limpus, D.T. Crouse, N.B. Frazer and L.B. Crowder. – 1996. Population model analysis for the loggerhead sea turtle, Caretta caretta, in Queensland. Wildl. Res., 23: 143-159. doi:10.1071/WR9960143

Heppell, S.S., M.L. Snover and L.B. Crowder. – 2003a. Sea turtle population Ecology. In: P.L. Lutz, J.A. Musick and J. Wyneken (eds.), The Biology of Sea Turtles, vol. II, pp. 275-306, CRC Press, Boca Raton.

Heppell, S.S., Crowder, L.B., Crouse, D.T., Epperly, S.P. and N.B. Frazer. – 2003b. Population Models for Atlantic Loggerheads: Past, Present, and Future. In: A.B. Bolten and B.E. Witherington (eds.), Loggerhead Sea Turtles, pp. 255-273, Smithsonian Books, Washington, D.C.

Jolly, G.M. – 1965. Explicit estimates from capture-recapture data with both death and immigration stochastic model. Biometrika, 52: 225-247.

Kopsida, H., D. Margaritoulis and D. Dimopoulos. – 2002. What marine turtle strandings can tell us. In: A. Mosier, A. Foley and B. Brost (comps.), Proc. 20th Ann. Symp. Sea Turtle Biol. Conserv. NOAA Technical Memorandum NMFS-SEFSC-477, pp. 207-209.

Laurent, L., P. Casale, M.N. Bradai, B.J. Godley, G. Gerosa, A.C. Broderick, W. Schroth, B. Schierwater, A.M. Levy, D. Freggi, E.M. Abd El-Mawla, D.A. Hadoud, H.E. Gomati, M. Domingo, M. Hadjichristophorou, L. Kornaraky, F. Demirayak and Ch. Gautier. – 1998. Molecular resolution of marine turtle stock composition in fishery bycatch: a case study in the Mediterranean. Mol. Ecol., 7: 1529-1542. doi:10.1046/j.1365-294x.1998.00471.x


Lebreton, J.-D., K.P. Burnham, J. Clobert and D.R. Anderson. – 1992. Modeling survival and testing biological hypotheses using marked animals: case studies and recent advances. Ecol. Monogr., 62: 67-118. doi:10.2307/2937171

Limpus, C.J. – 1990. Puberty and first breeding in Caretta caretta. In: T.H. Richardson, J.I. Richardson and M. Donnelly (comps), Proc. 10th Ann. Works. Sea Turtle Biol. Conserv. NOAA Technical Memorandum NMFS-SEFC-278, pp. 81-83.

Limpus, C.J. – 1992. Estimation of tag loss in marine turtle research. Wildl. Res., 19(4): 457-469. doi:10.1071/WR9920457

Lutcavage, M.E., Plotkin, P., Witherington, B., Lutz, P.I., 1997. Human impact on sea turtle survival. In: P.L. Lutz and J.A. Musick (eds.), The biology of sea turtles, pp. 387-411, CRC Press, LLC.

Margaritoulis, D., R. Argano, I. Baran, F. Bentivegna, M.N. Bradai, J.A. Caminas, P. Casale, G. De Metrio, A. Demetropoulos, G. Gerosa, B. Godley, J. Houghton, L. Laurent and B. Lazar. – 2003. Loggerhead turtles in the Mediterranean Sea: present knowledge and conservation perspectives. In: A.B. Bolten and B. Witherington (eds.), Loggerhead Sea Turtles, pp. 175-198,

Smithsonian Institution Press, Washington, DC, USA. Pollock, K.H., J.D. Nichols, C. Brownie and J.E. Hines. – 1990. Statistical inference for capture-recapture experiments. Wildl. Monogr., 107.

Schaub, M. and R. Pradel. – 2004. Assessing the relative importance of different sources of mortality from recoveries of marked animals. Ecology, 85(4): 930-938. doi:10.1890/03-0012

Schroth, W., B. Streit and B. Schierwater. – 1996. Evolutionary handicap for turtles. Nature, 384: 521-522. doi:10.1038/384521a0

Seber, G.A.F. – 1965. A note on the multiple recapture census. Biometrika, 52: 249-259.

Seminoff, J.A., T.T. Jones, A. Resendiz, W.J. Nichols and M.Y. Chaloupka. – 2003. Monitoring green turtles (Chelonia mydas) at a coastal foraging area in Baja California, Mexico: Using multiple indices to describe population status. J. Mar. Biol. Ass. UK, 83: 1355-1362. doi:10.1017/S0025315403008816

Tavecchia, G., R. Pradel, J.-D. Lebreton, A.L. Johnson and J.-Y. Mondain-Monval. – 2001. The effect of lead exposure on survival of adult mallards in the Camargue, southern France. J. Appl. Ecol., 38: 1197-1207. doi:10.1046/j.0021-8901.2001.00684.x

White, G.C. and K.P. Burnham. – 1999. Program MARK: survival estimation from populations of marked animals. Bird. Study, 46(Suppl.): 120-138.

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