Zoological Studies

Vol. 61, 2022

(update: 2022.7.11)

Abundance Trends and Nesting Biology of Green Turtles Chelonia mydas (Testudines: Cheloniidae) During Ten Consecutive Breeding Seasons at Akyatan Beach, Turkey

Can Yılmaz1,2,*, Ayşe Oruç2, and Oguz Turkozan3,4
doi:-

1Vocational School of Health Services, Hakkâri University, Keklikpınar Mahallesi Kampüs Caddesi 30000 Hakkâri, Turkey. *Correspondence: E-mail: canyilmaz@hakkari.edu.tr (Yılmaz)
2WWF Turkey, Buyuk Postane Caddesi No:19 Kat 5, 34420 Bahcekapi, Eminonu, Istanbul, Turkey. E-mail: aoruc@wwf.org.tr (Oruç)

3Department of Biology, Faculty of Science and Arts, Aydın Adnan Menderes University, 09010 Aydın, Turkey. E-mail: oguz.turkozan@gmail.com (Turkozan)
4Cyprus Wildlife Research Institute, Kyrenia, Northern Cyprus, Research Associate, Cyprus

Received 21 February 2022 / Accepted 25 June 2022
Communicated by Yoko Nozawa

Data obtained from long-term survey studies are valuable for assessing the population status and trends in critical populations of threatened species, like sea turtles. Akyatan beach is one of the most important green turtle nesting beaches in the Mediterranean and has been monitored since 2006 without interruption. The beach is 22 km long and more than 100 m wide at some points, and both loggerhead and green turtles nests on the beach. However, the loggerhead nesting is very limited in comparison to green turtles. A total of 3866 C. mydas nests were recorded during ten consecutive years at Akyatan beach, with a mean of 387 ± 127 nests (range = 201–559). The average nesting density was 17.6 nests km-1 (range = 9.1–25.4 nests km-1). In the 3309 nests, a total of 355,259 eggs were counted. The overall mean clutch size was 112 ± 26.10 eggs. Of these eggs, 50.80% hatched (depredated nests included), and 78.07% of them were able to reach the sea. The overall mean hatching success was 73.07 ± 26.20%. The overall mean incubation duration was 51.4 ± 3.5 days. The clutch sizes and hatching success differed between years, and there was a significant trend in mean incubation duration to decrease over ten years of study. A total of 1585 green turtle nests (41.02% of nests) were totally or partially depredated by golden jackals and wild boar, while other predators depredated 20.5% of hatchlings. The nesting data obtained since 2006 showed strong annual fluctuations ranging from 170 (in 2007) to 562 (in 2006) with a slightly increasing but statistically insignificant trend (r = 0.94, p > 0.05). The main threats to the population were depredation by jackals and wild boars.

Key words: Endangered species, Conservation, Sea turtles.

Citation: Yılmaz C, Oruç A, Türkozan O. 2022. Abundance trend and nesting biology of green turtles Chelonia mydas (Testudines: Cheloniidae) during ten consecutive nesting seasons at Akyatan Beach, Turkey. Zool Stud 61:53.