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

Imed Jribi,Atef Ouergui,Abdelmaula Hamza,Almoktar Saied

doi:10.3989/scimar.03855.28b

Abstract

SUMMARY: 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.

Highlights

Marine turtles are an example of a species that is diminishing in numbers as a result of the degradation of the living and nesting habitats, incidental catches, and pollution (Lutcavage et al 1997).Significant resources are currently devoted to numerous conservation and management projects at nesting areas
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 maximum temperature during this period increased to between 0.6°C and 3.5°C, while the mean temperature increased during the middle third of the incubation period compared with the first third and continued to increase during the last third

Summary

Introduction

Marine turtles (family Cheloniidae) are an example of a species that is diminishing in numbers as a result of the degradation of the living and nesting habitats, incidental catches, and pollution (Lutcavage et al 1997).Significant resources are currently devoted to numerous conservation and management projects at nesting areas. With the present trends and potential impacts of global warming, increased temperature can affect the sex ratio in marine turtles as well as in many other reptile species (Janzen and Paukstis 1991), as it is determined by the prevailing environmental conditions (mainly nest temperature) during the embryonic development (TSD for temperature-dependent sex determination). This means that warming temperatures could lead to a higher production of female hatchlings

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Conclusion