Impact of tropical forest logging on the reproductive success of leatherback turtles

Logging in tropical forests causes, among other impacts, the accumulation of organic debris on many beaches after it is carried to the coast by rivers and concentrated by oceanographic processes. Such accumulated beach organic material (ABOM) has the potential to exert important negative effects on the reproductive success of marine turtles. Females must be able to exit the ocean and cross sandy beaches to nest and, as no parental care is provided, hatchlings must cross the beach to reach the sea following emergence from the nest. We investigated how ABOM affects nest site selection and hatchling dispersal at a globally important rookery for leatherback turtles Dermochelys coriacea in Colombia. Detailed surveys were combined with field experiments in which the amount of ABOM was manipulated. Areas with higher ABOM had a similar rate of nesting, but females spent significantly more time in nest camouflage, suffered external lesions and nested closer to the shoreline, increasing the risk of egg mortality caused by flooding and erosion. When ABOM was manually removed from several beach sectors, nest site selection moved towards areas with less risk of flooding or tidal erosion. In nesting seasons with higher ABOM, a lower rate of female recapture was experienced, suggesting a greater dispersion of nests, possibly emigration. ABOM represents a barrier for many hatchlings, causing them to spend significantly more time reaching the sea, thereby increasing their energy output and their risk of predation or desiccation.