Primary Sex Ratio Estimation and the Feminizing Effect of Metabolic Heating in Green Sea Turtle (Chelonia mydas) Nests at Samandağ Beach Samandağ Kumsalı’ndaki Yeşil Deniz Kaplumbağası (Chelonia mydas) Yuvalarında Birincil Eşey Oranının Tahmini ve Metabolik Isınmanın Dişileştirici Etkisi
Commagene Journal of Biology, cilt.10, sa.1, ss.273-280, 2026 (Scopus, TRDizin)
- Yayın Türü: Makale / Tam Makale
- Cilt numarası: 10 Sayı: 1
- Basım Tarihi: 2026
- Doi Numarası: 10.31594/commagene.1947796
- Dergi Adı: Commagene Journal of Biology
- Derginin Tarandığı İndeksler: Scopus, TR DİZİN (ULAKBİM)
- Sayfa Sayıları: ss.273-280
- Anahtar Kelimeler: Chelonia mydas, Incubation temperature, metabolic heating, temperature-dependent sex determination
- Açık Arşiv Koleksiyonu: AVESİS Açık Erişim Koleksiyonu
- Hakkari Üniversitesi Adresli: Evet
Özet
This study investigated the primary sex ratios of green sea turtle (Chelonia mydas) nests at Samandağ Beach, Türkiye during the 2018 nesting season. Sex ratios were estimated using a symmetric logistic Temperature-Dependent Sex Determination (TSD) model applied to temperature data recorded throughout the thermosensitive period (TSP). In addition, the contribution of embryonic metabolic heating and its feminizing effect on sex ratio were evaluated. Nest temperatures were monitored in 12 nests; in five of these nests, additional temperature loggers were placed in adjacent control sand at the same depth and recorded simultaneously to quantify metabolic heat production. Incubation temperatures increased significantly over the course of embryonic development (p <0.001), rising from 27.50–30.06°C during the first third of incubation to a mean of 32.27°C in the final third, with a maximum of 33.39 ± 0.66°C. Estimated primary sex ratios showed a strong female bias (mean: 87.71% ± 16.47), with only one nest producing a male-biased outcome (42.22% female at 29.07°C). While metabolic heating was negligible during early incubation, it increased markedly in later stages, elevating nest temperatures by an average of 1.99 ± 0.78°C above ambient sand temperatures during the final third. The feminizing effect of metabolic heating averaged 8.75% ± 10.59 and ranged from 1.14% to 27.36% among nests. This effect was most pronounced when ambient sand temperatures were close to the transitional range of the TSD reaction norm. Overall, the findings confirm a strongly female-biased sex ratio at the Samandağ Beach and demonstrate that metabolic heating can alter hatchling sex ratios beyond estimates based solely on sand temperature. These results highlight the importance of considering both environmental and metabolic factors in conservation assessments of Eastern Mediterranean C. mydas populations.