The effect of nest abundance of Loggerhead turtles on the nest predation rate of ghost crabs in Cabo Verde

The Loggerhead sea turtle (Caretta caretta) is facing intense nest predation globally. The subpopulation nesting on the Cabo Verde Archipelago, which is categorized as Endangered on the IUCN List, has been encountering high predation rates caused by ghost crabs (Ocypode cursor), the main predator on these oceanic islands. This study investigates the effect of nest abundance of Loggerheads on nest predation by ghost crabs on Boa Vista, Cabo Verde, from 2013 to 2021. Boa Vista hosts around 60% of the Loggerhead nests in Cabo Verde which is one of the world's largest Loggerhead rookeries. The nest abundance was recorded during night patrol and daily beach surveys at dawn. The predation of ghost crabs was evaluated using natural Loggerhead nests that were checked daily for any evidence of predation, inundation, erosion, or any other relevant disturbances to the nest. The clutch size of these nests was counted during oviposition and the nests were exhumed after the incubation period to assess the number of hatched, enclosed, and missing eggs. The interannual variability in Loggerhead nests was high, ranging from 1123 to 33496 nests. The nest mortality by crab predation was strongly negatively correlated to the nest abundance. Seasons with a low nest abundance showed high crab predation rates of up to 75%, whereas in seasons with high nest abundance crab predation rates as low as 4% were observed. Higher nest abundance might exceed the capacity to consume sea turtle eggs of the ghost crab population on the studied beach. Through predator satiation caused by high nest abundance, the risk of predation and the extent of the predation may be reduced. The findings give an interesting insight into this predator-prey interaction but also highlight the importance of conservation efforts in reducing predation, especially for areas and seasons with low sea turtle nest abundance. ; A tartaruga-cabeçuda (Caretta caretta) enfrenta intensa predação de ninhos em todo o mundo. A subpopulação que nidifica no Arquipélago de Cabo Verde, ...