Research Article

Primary Sex Ratio Estimation and the Feminizing Effect of Metabolic Heating in Green Sea Turtle (Chelonia mydas) Nests at Samandağ Beach

Volume: 10 Number: 1 July 14, 2026
EN TR

Primary Sex Ratio Estimation and the Feminizing Effect of Metabolic Heating in Green Sea Turtle (Chelonia mydas) Nests at Samandağ Beach

Abstract

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.

Keywords

Ethical Statement

Ethics committee approval is not required for this study

Thanks

I would like to thank Prof. Dr. Bektaş Sönmez for granting access to the Samandağ nesting beach and for his support during fieldwork. This study was conducted under the authorization of the Republic of Türkiye Ministry of Agriculture and Forestry, 7th Regional Directorate (Hatay Province).

References

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Details

Primary Language

English

Subjects

Ecology (Other)

Journal Section

Research Article

Publication Date

July 14, 2026

Submission Date

May 9, 2026

Acceptance Date

June 30, 2026

Published in Issue

Year 2026 Volume: 10 Number: 1

APA
Karaman, S. (2026). Primary Sex Ratio Estimation and the Feminizing Effect of Metabolic Heating in Green Sea Turtle (Chelonia mydas) Nests at Samandağ Beach. Commagene Journal of Biology, 10(1). https://doi.org/10.31594/commagene.1947796
AMA
1.Karaman S. Primary Sex Ratio Estimation and the Feminizing Effect of Metabolic Heating in Green Sea Turtle (Chelonia mydas) Nests at Samandağ Beach. Comm. J. Biol. 2026;10(1). doi:10.31594/commagene.1947796
Chicago
Karaman, Sezgin. 2026. “Primary Sex Ratio Estimation and the Feminizing Effect of Metabolic Heating in Green Sea Turtle (Chelonia Mydas) Nests at Samandağ Beach”. Commagene Journal of Biology 10 (1). https://doi.org/10.31594/commagene.1947796.
EndNote
Karaman S (July 1, 2026) Primary Sex Ratio Estimation and the Feminizing Effect of Metabolic Heating in Green Sea Turtle (Chelonia mydas) Nests at Samandağ Beach. Commagene Journal of Biology 10 1
IEEE
[1]S. Karaman, “Primary Sex Ratio Estimation and the Feminizing Effect of Metabolic Heating in Green Sea Turtle (Chelonia mydas) Nests at Samandağ Beach”, Comm. J. Biol., vol. 10, no. 1, July 2026, doi: 10.31594/commagene.1947796.
ISNAD
Karaman, Sezgin. “Primary Sex Ratio Estimation and the Feminizing Effect of Metabolic Heating in Green Sea Turtle (Chelonia Mydas) Nests at Samandağ Beach”. Commagene Journal of Biology 10/1 (July 1, 2026). https://doi.org/10.31594/commagene.1947796.
JAMA
1.Karaman S. Primary Sex Ratio Estimation and the Feminizing Effect of Metabolic Heating in Green Sea Turtle (Chelonia mydas) Nests at Samandağ Beach. Comm. J. Biol. 2026;10. doi:10.31594/commagene.1947796.
MLA
Karaman, Sezgin. “Primary Sex Ratio Estimation and the Feminizing Effect of Metabolic Heating in Green Sea Turtle (Chelonia Mydas) Nests at Samandağ Beach”. Commagene Journal of Biology, vol. 10, no. 1, July 2026, doi:10.31594/commagene.1947796.
Vancouver
1.Sezgin Karaman. Primary Sex Ratio Estimation and the Feminizing Effect of Metabolic Heating in Green Sea Turtle (Chelonia mydas) Nests at Samandağ Beach. Comm. J. Biol. 2026 Jul. 1;10(1). doi:10.31594/commagene.1947796