Population dynamics of the coconut crab Birgus latro on Aldabra Atoll, Seychelles

Aldabra Atoll, Seychelles, hosts one of the largest and most stable populations of the coconut crab Birgus latro, the world's largest terrestrial arthropod. A decade-long study (2007–2016) revealed an average density of 23.7 ± 1.1 individuals per hectare in Picard Island’s coastal area, suggesting a population of around 5,000 crabs—likely an underestimate due to the species' cryptic behavior. The population exhibited high spatial and temporal variability, with a male-biased sex ratio (3:1) and sexual dimorphism, where males were significantly larger than females. Breeding synchronized with the lunar cycle and overlapped with the wet season (December–March). Color polymorphism was observed in a 4:1:1 ratio of orange, blue, and intermediate forms. These findings underscore Aldabra’s role as a critical refuge for B. latro, potentially serving as a natural source population for regional conservation efforts.

Appoo, J., Cagua, E., van de Crommenacker, J., Burt, A., Pistorius, P., Taylor, F., Richards, H., Haupt, P., Doak, N., Fleischer-Dogley, F., & Bunbury, N. (2021). Population dynamics of the coconut crab Birgus latro on Aldabra Atoll, Seychelles. Marine Ecology Progress Series, 665, 103–113. https://doi.org/10.3354/meps13672