Long-term changes in adult size of green turtles at Aldabra Atoll and implications for clutch size, sexual dimorphism and growth rates

Green turtle populations worldwide have faced declines in mean nesting size, raising concerns about reduced reproductive output. However, a 21-year study at Aldabra Atoll reveals that despite a slight decline in the curved carapace length of nesting females—from 111.43 cm to 110.08 cm over two decades—the total number of eggs produced annually increased from 1.3 million to 2.0 million, offsetting potential impacts on clutch size. The study analyzed over 4,500 individual measurements and found a mean growth rate of 0.14 cm per year for 391 recaptured turtles. Sexual dimorphism was also documented, with females consistently larger than males in carapace length (ratio: 1.09), width (1.10), and weight (1.25). These findings suggest that while adult size may decrease over time, compensatory increases in nesting numbers can sustain reproductive output.

Mortimer, J. A., Appoo, J., Bautil, B., Betts, M., Burt, A. J., Chapman, R., Currie, J. C., Doak, N., Esteban, N., Liljevik, A., Mahoune, J. T., Onezia, C., Pistorius, P., Richards, H., Samedi, U., Sanchez, C. L., Seabrook, W., Underwood, A., van de Crommenacker, J., et al. (2022). Long-term changes in adult size of green turtles at Aldabra Atoll and implications for clutch size, sexual dimorphism and growth rates. Marine Biology, 169(10). https://doi.org/10.1007/s00227-022-04111-1