Abstract
Based on nesting data over a 12-year period (1993–2004), this study points to a negative population trend of the loggerhead turtle population at Fethiye beach, Turkey. The number of nests fluctuated from a maximum of 186 in 1995 to a minimum of 58 in 2004. Successively smaller peaks at 3-year intervals were followed by successively smaller troughs. Two analyses—one representing a dampened oscillation, the other retaining the period and the amplitudes of the nesting cycles—predict that nest number will drop to about 40–50 by 2015, i.e. to about 22–27% of its highest value. This drop at Fethiye does not correspond with a visible increase at neighboring beaches, leading to the interpretation that the number of nesting turtles here is declining. Moreover, the carapace size of emerging adult females is apparently decreasing, as are clutch sizes. Such a potential negative trend at a key Turkish nesting beach is cause for concern, an incentive for continued study, and a call for more coordinated and effective conservation programs in this region of the Mediterranean.
Similar content being viewed by others
References
Baran İ, Kasparek M (1989) Marine turtles Turkey. Status survey 1988 and recommendations for conservation and management. Heidelberg, Germany
Baran İ, Türkozan O (1996) Nesting activity of the loggerhead turtle, Caretta caretta, on Fethiye Beach, Turkey in 1994. Chelonian Conserv Biol 2(1):93–96
Bjorndal AK, Wetherall JA, Bolten AB, Mortimer JA (1999) Twenty-six years of green turtle nesting at Tortuguero, Costa Rica: an encouraging trend. Conser Biol 13(1): 126–134
Broderick AC, Godley BJ (1996) Population and nesting ecology of the Green Turtle, Chelonia mydas, and the Loggerhead Turtle, Caretta caretta, in northern Cyprus. Zool Middle East 13:27–46
Broderick AC, Glen F, Godley BJ, Hays GC (2002) Estimating the number of Green and Loggerhead Turtles nesting annually in the Mediterranean. Oryx 36(3):1–9
Canbolat AF (2004) A review of sea turtle nesting activity along the Mediterranean coast of Turkey. Biol Conser 116:81–91
Chaupka M (2001) Historical trends, seasonality and spatial synchrony in green sea turtle egg production. Biol Conserv 101:263–279
Clarke M, Campbell AC, Hameid WS, Ghoneim S (2000) Preliminary report on the status of marine turtle nesting populations on the Mediterranean coast of Egypt. Biol Conserv 94:363–371
Groombridge B (1990) Marine turtles in the Mediterranean: distribution, population status, conservation. Council of Europe Nature and Environment Series, Strasbourg
Hatase H, Goto K, Sato K, Bando T, Matsuzawa Y, Sakamoto W (2002) Using annual body size fluctuations to explore potential causes for the decline in nesting population of the loggerhead turtle Caretta caretta at Senri Beach, Japan. Mar Ecol Prog Ser 245:299–304
Hays GC (2000) The implications of variable remigration intervals for the assessment population size in marine turtles. J Therm Biol 206:221–227
Heppel SS, Snover ML, Crowder LB (2003) Sea turtle population ecology. In: Lutz P, Musick JA, Wyneken J (eds) Biology of sea turtles vol II, Florida, USA, pp 275–299
Kaska Y (2004) Deniz kaplumbağalarını koruma planı projesi. Muğla-Dalaman Bölgesi’ndeki kıyı ve sulak alan ekosistemlerinin araştırılması II. alt projesi. T.C. Çevre ve Orman Bakanlığı, Ankara
Kasparek M (1993) Survey of the Mediterranean coast between Alexandria and El-Salum, Egypt. Mar Turtle Newsl 63:8–9
Kasparek M (1995) The nesting of marine turtles on the coast of Syria. Zool Middle East 11:51–62
Kuller Z (1999) Current status and conservation of marine turtles on the Mediterranean coast for Israel. Mar Turtle Newsl 86:3–5
Laurent L, Navira S, Grissac DJ, Bradai MN (1990) Les tortues marines des Tunisie: premiers données. Bull Soc Herp Fr 53:1–17
Laurent L, Bradai MN, Hadoud DA, Gomati HM (1995) Marine turtle nesting activity assessment on Libyan coast. Phase I: survey of the coast between Egyptian border and Sirte- RAC/SPA (MAP-UNEP), Tunis
Margaritoulis D (2000) An estimation of the overall nesting activity of the loggerhead turtle in Greece. In: Abreu-Grobois FA, Briseño-Dueñas R, Márquez-Millán R, Sarti-Mártinez L (eds) Proceedings of the 18th International Sea Turtle Symposium, NOAA Technical Memorandum NMFS-SEFSC-436 Mazatlan, Mexico, pp 48–50
Margaritoulis D, Rees AF (2001) The loggerhead turtle, Caretta caretta, population nesting in Kyparissia Bay, Peloponnesus, Greece: results of beach surveys over seventeen seasons and determination of the core nesting habitat. Zool Middle East 24:75–90
Margaritoulis D, Argano R, Baran İ, Bentivegna F, Bradai MN, Camiňas JA, Casale P, De Metrio G, Demetropoulos A, Gerosa G, Godley BJ, Haddound DA, Houghton J, Laurent L, Lazar B (2003) Loggerhead turtles in the Mediterranean Sea: present knowledge and conservation perspectives. In: Bolten AB, Witherington BE (eds) Loggerhead sea turtles, Washington, USA, pp 175–198
Miller JD (1997) Reproduction in sea turtles. In: Lutz P, Musick JA (eds) Biology of sea turtles, Florida, USA, pp 51–81
Mortimer JA, Carr A (1987) Reproduction and migrations of the Ascension Island green turtle (Chelonia mydas). Copeia 1987:103–113
National Research Council (1990) Decline of sea turtles. Causes and prevention. National Academy Press, Washington, p 259
Newburry N, Khalil M, Venizelos L (2002) Population status and conservation of marine turtles at El-Mansuri, Lebanon. Zool Middle East 27:47–60
Oruç A, Türkozan O, Durmuş SH (2003) Deniz kaplumbağalarının izinde deniz kaplumbağası yuvalama kumsalları değerlendirme raporu 2003. WWF-Turkey, İstanbul, Turkey
Sato K, Bando T, Matsuzawa Y, Tanaka H, Sakamoto W, Minamikawa S, Goto K (1997) Decline of the loggerhead turtle, Caretta caretta, nesting on Senri beach in Minabe, Wakayama, Japan. Chelonian Conserv Biol 2(4):600–603
Shanker K, Pandav B, Choudhury BC (2003) An assessment of the olive ridley (Lepidochelys olivacea) nesting population in Orissia, India. Biol Conserv 115:149–160
Solow RA, Bjorndal KA, Bolten AB (2002) Annual variation in nesting numbers of marine turtles: the effect of sea turtle surface temperature on remigration intervals. Ecol Lett 5:742–746
Türkozan O, Baran İ (1996) Research on the loggerhead turtle, Caretta caretta, of Fethiye Beach. Turk J Zool 20:183–188
Türkozan O (2000) Reproductive ecology of the loggerhead turtle, Caretta caretta, on Fethiye and Kızılot beaches, Turkey. Chelonian Conserv Biol 3(4):686–692
Türkozan O, Durmuş SH (2000) A feeding ground for juvenile green turtles, Chelonia mydas, on the western coast of Turkey. Brit Herp Soc Bull 71:1–5
Türkozan O, Taşkavak E, Ilgaz Ç (2003) A review of the biology of the loggerhead turtle, Caretta caretta, at five major nesting beaches on the Southwestern Mediterranean Coast of Turkey. Herpet J 13:27–33
Acknowledgements
We thank all the volunteers from Dokuz Eylül, Adnan Menderes, Pamukkale and Vienna Universities for their help during the fieldwork. M.S. thanks his past and present field coordinators Nadja Ziegler and Christine Fellhofer for their crucial support and acknowledges sponsorship by the ‘Society of the Friends of Schoenbrunn Zoo’ and Gulet Touropa Touristik. We are very grateful to Prof. Dr. Johann Hohenegger of the Department of Paleontology in Vienna for calculating and representing the long-term nesting trend in Fig. 2. Fritz Sobotka drew the final version of Fig. 1.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Ilgaz, Ç., Türkozan, O., Özdemir, A. et al. Population Decline of Loggerhead Turtles: Two Potential Scenarios for Fethiye Beach, Turkey. Biodivers Conserv 16, 1027–1037 (2007). https://doi.org/10.1007/s10531-006-9049-2
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s10531-006-9049-2