Sex ratio estimations of loggerhead marine turtle hatchlings by incubation duration and nest temperature at Sirte beaches (Libya)


  • Imed Jribi Sfax Faculty of Sciences, University of Sfax
  • Abdelmaula Hamza Libyan Sea Turtle Program-Environment General Authority
  • Almoktar Saied Libyan Sea Turtle Program-Environment General Authority
  • Atef Ouergui Regional Activity Centre for Specially Protected Areas



loggerhead turtle, hatchlings, sex ratio, incubation duration, nest temperature, Libya


Hatchling sex ratios in loggerhead marine turtles (Caretta caretta) were estimated on the beaches near Sirte (Libya), using two methods: incubation duration and nest mean temperature during the middle third of the incubation period. Electronic temperature/humidity loggers were deployed at a total of 13 selected nests at Al-Ghbeba, Al-Thalateen, west of Al- Thalateen, Shash and Al-Arbaeen. The incubation period ranged from 47 to 58 days and average temperature ranged from 29°C to 31.8°C. The maximum temperature during this period increased to between 0.6°C and 3.5°C, while the mean temperature also increased during the middle third of the incubation period compared with the first third and continued to increase during the last third. As expected, this study showed that the temperature in the nest decreased with increasing depth of the nest. The results showed a female-dominated sex ratio at 85.4% on the basis of incubation duration and 70.4% on the basis of mean temperature. These findings support the reported highly female-skewed sex ratios in the Mediterranean and elsewhere.


Download data is not yet available.


Adam V., Tur C., Rees A.F., Tomas J. 2007. Emergence pattern of loggerhead turtle (Caretta caretta) hatchlings from Kyparissia bay, Greece. Mar. Biol. 151: 1743-1749.

Booth D.T., Astill K. 2001. Temperature variation within and between nests of the green sea turtle, Chelonia mydas (Chelonia: Cheloniidae) on Heron Island, Great Barrier Reef. Aust. J. Zool. 49: 71-84.

Bradai M.N., Nicolosi P., Casale P., Jribi I., Turchetto M., El Abed A. 2004. The presence of leatherback turtles in the central Mediterranean area: data from Italy and Tunisia. Biol. Mar. Med. 11(2): 750-753.

Casale P., Nicolosi P., Freggi D., Turchetto M., Argano R. 2003. Leatherback turtles (Dermochelys coriacea) in Italy and in the Mediterranean basin. Herpetol. J. 13(3): 135-139.

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: 145-148.

Casale P., Lazar B., Pont S., Tomas J., Zizzo N., Alegre F., Badillo J., Di Summa A., Freggi D., Lackovic G., Raga J.A, Rositani L., Tvrtkovic N. 2006. Sex ratios of juvenile loggerhead sea turtles Caretta caretta in the Mediterranean Sea. Mar. Ecol. Prog. Ser. 324: 281-285.

Casale P., Margaritoulis D. (eds) 2010. Sea turtles in the Mediterranean: Distribution, threats and conservation priorities. Gland, Switzerland, IUCN Press, 294 pp.

Ewert M.A., Jackson D.R., Nelson C.E. (1994) Patterns of temperature-dependent sex determination in turtles. J. Exp. Zool. 270: 3-15.

GIEC. 2007. Bilan 2007 des changements climatiques. Contribution des Groupes de travail I, II et III au quatrième Rapport d'évaluation du Groupe d'experts intergouvernemental sur l'évolution du climat [Équipe de rédaction principale, Pachauri, R.K. et Reisinger, A. GIEC, Genève, Suisse, …, 103 pp.].

Godfrey M.H., Mrosovsky N. 1997. Estimating the time between hatching of sea turtles and their emergence from the nest. Chel. Conserv. Biol. 2: 581-585.

Godfrey M.H., Barreto R., Mrosovsky N. 1997. Metabolically generated heat of developing eggs and its potential effect on sex ratio of sea turtle hatchlings. J. Herpetol. 31: 616-619.

Godley B.J., Broderick A.C., Mrosovsky N. 2001. Estimating hatchling sex ratios of loggerhead turtles in Cyprus from incubation durations. Mar. Ecol. Prog. Ser. 210:195-201.

Hamza A. 2010. Libya. In: Casale P., Margaritoulis D. (eds), Sea turtles in the Mediterranean: Distribution, threats and conservation priorities. Gland, Switzerland, IUCN Press, pp. 157-170.

Hamza A., El Ghmati H. 2006. Conservation of Marine Turtles nesting at three sites West of Sirte, Libya. Final report. The Regional Activity Centre for Specially Protected Areas (UNEP-MAP-RAC/SPA), Tunis. 35 pp.

Hanson J., Wibbels T., Martin R.E. 1998. Predicted female bias in sex ratios of hatchling loggerhead sea turtles from a Florida nesting beach. Can. J. Zool. 76: 1850-1861.

Hawkes, L.A., Broderick A.C., Godfrey M.H., Godley B.J. 2009. Climate change and marine turtles. Endang. Species Res. 7: 137-154.

Houghton, J.D.R., Hays, G.C. 2001. Asynchronous emergence by loggerhead turtle Caretta caretta hatchlings. Naturwissenschaften 88: 133-136.

Janzen F.J, Paukstis G.L. 1991. Environmental sex determination in reptiles: ecology, evolution, and experimental design. Q. Rev. Biol. 66: 149-179.

Jribi I., Ben Hassine S., Bradai M.N., Bouain A. 2012. Estimating hatchling sex ratios of loggerhead turtles from incubation duration and nest temperatures at Kuriat island, Tunisia. In: Bradai M.N., Casale P. (eds), Proceedings of the Third Mediterranean Conference on Marine Turtles, Barcelona Convention - Bern convention - Bonn Convention (CMS). Tunis, Tunisia, pp. 82-84.

Kasparek M., Godley B.J., Broderick A.C. 2001. Nesting of the Green Turtle, Chelonia mydas, in the Mediterranean: a review of status and conservation needs. Zool. Middle East 24: 45-74.

Kaska Y., Downier R., Tippett R., Furness R.W. 1998. Natural temperature regimes for Loggerhead and Green turtle nests in the Eastern Mediterranean. Can. J. Zool. 76: 723-729.

Kaska Y., Ilgaz Ç., Özdemir A., Baskale E., TurkozanO., Baran I., Stachozitsch M. 2006. Sex ratio estimations of loggerhead sea turtle hatchlings by histological examination and nest temperatures at Fethiye beach, Turkey. Naturwissenschaften 93: 338-343.

Laurent L., Bradai M.N., Haddoud D.A., El Gomati H.M. 1997. Assessment of sea turtle nesting activity in Libya. Mar. Turtle News 76: 2-6.

Laurent L., Bradai M.N., Haddoud D., El Gomati H.M., Hamza A. 1999. Marine turtle nesting activity assessment on Libyan coasts. Phase 3: Survey of the coast to the west of Misratah. Joint Project of: Marine Biology Research Centre (Tajura, Libya), MEDASSET, RAC/SPA (MAP-UNEP), TCEP (Tripoli), WWF International Mediterranean Programme. 47 pp.

Lescure J., Delaugerre M., Laurent L. 1989. La nidification de la tortue luth, Dermochelys coriacea (Vandelli, 1761) en Mediterranée. Bul. Soc. Herpétol. France. 50: 9-18.

Lutcavage M.E., Plotkin P., Witherington B. and Lutz P.L. 1997. Human Impacts on sea Turtle Survival. In: Lutz J.A., Musick J.A. (eds), The biology of sea turtles. CRC Press, Boca Raton, Florida, USA, pp. 387-411.

Margaritoulis D. 1986. Captures and strandings of the leatherback sea turtle, Dermochelys coriacea, in Greece (1982-1984). J. Herpetol. 20(3): 471-474.

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

Mrosovsky N., Pieau C. 1991. Transitional range of temperature, pivotal temperatures and thermosensitive stages for sex determination in reptiles. Amphibia-Reptilia 12: 169-179.

Mrosovsky N., Baptistotte C., Godfrey M.H. 1999. Validation of incubation duration as an index of the sex ratio of hatchling sea turtles. Can. J. Zool. 77: 831-835.

Mrosovsky N., Kamel S., Rees A.F., Margaritoulis D. 2002. Pivotal temperature for loggerhead turtles (Caretta caretta) from Kyparissia Bay, Greece. Can. J. Zool. 80: 2118-2124.

Mrosovsky N., Kamel S.J., Diez C.E., Van Dam R.P. 2009. Methods of estimating natural sex ratios of sea turtles from incubation temperatures and laboratory data. Endang. Species. Res. 8: 147-155.

Owens D.W., Hendrickson J.R, Lance V., Callard I.P. 1978. A technique for determining sex of immature Chelonia mydas using a radioimmunoassay. Herpetologica 34: 270-273.

Öz M., Erdogan A., Kaska Y., Du.sen S., Aslan A., Sert H., Yavuz M., Tunç M. R. 2004. Nest temperatures and sex-ratio estimates of loggerhead turtles at Patara beach on the southwestern coast of Turkey. Can. J. Zool. 82: 94-101.

Rees AF, Margaritoulis D. 2004. Beach temperatures, incubation durations and estimated hatchling sex ratio for loggerhead sea turtle nests in southern Kyparissia Bay, Greece. Testudo 6: 23-36.

Rees A.F., Margaritoulis D., Newman R., Riggall T.E., Tsaros P., Zbinden J.A., Godley B.J. 2013. Ecology of loggerhead marine turtles Caretta caretta in a neritic foraging habitat: movements, sex ratios and growth rates. Mar. Biol. 160: 519-529.

Richardson J.I. 1999. Priorities for studies of reproduction and nest biology. 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 no. 4, pp. 9-11.

Schleich H. 1987. Contributions to the herpetology of Kouf National Park (NE-Libya) and adjacent areas. Spixiana 10(1): 37-80.

Wibbels T. 2003. Critical approaches to sex determination in sea turtles. In: Lutz P.L., Musick J.A., Wyneken J. (eds), The biology of sea turtles, Vol II. CRC Press, Boca Raton, FL, pp. 103-134.

Witt M.J., Hawkes L.A., Godfrey M.H., Godley B.J., Broderick A.C. 2010. Predicting the impacts of climate change on a globally distributed species: the case of the loggerhead turtle. J. Exp. Biol. 213: 901-911.

Wood J.R., Wood F.E., Critchley K.H., Wildt D.E., Bush M. 1983. Laparoscopy of the green sea turtle, Chelonia mydas. J. Herpetol. 6: 323-327.

Work T.M. 2000. Sea turtle necropsy manual for biologists in remote refuges. US Geological Survey, National Wildlife Health Center, Hawaii Field Station, Honolulu, HI. Yntema C. L., Mrosovsky N. 1980. Sexual differentiation in hatchling loggerheads (Caretta caretta) incubated at different controlled temperatures. Herpetologica 36(1): 33-36.

Zbinden J.A., Margaritoulis D., Arlettaz R. 2006. Metabolic heating in Mediterranean loggerhead sea turtle clutches. J. Exp. Mar. Biol. Ecol. 334: 151-157.

Zbinden J.A, Davy C., Margaritoulis D., Arlettaz R. 2007. Large spatial variation and female bias in the estimated sex ratio of loggerhead sea turtle hatchlings of a Mediterranean rookery. Endang. Species Res. 3: 305-312.




How to Cite

Jribi I, Hamza A, Saied A, Ouergui A. Sex ratio estimations of loggerhead marine turtle hatchlings by incubation duration and nest temperature at Sirte beaches (Libya). scimar [Internet]. 2013Dec.30 [cited 2022Aug.10];77(4):617-24. Available from: