Density-dependent nest destruction and population fluctuations of Guianan leatherback turtles

Approximately 40% of the world's leatherback marine turtles (Dermochelys coriacea) nest in Suriname and French Guiana. Trends in nest numbers reconstructed for the last 34 years indicate several up and down events. We undertook computer simulations to determine whether a density-dependent phenomenon might be involved because the period of high-density nesting coincides with a high level of nest destruction by nesting females. The parameters of density-dependent nest destruction were calculated for the Yalimapo-Awala beach. We show that: (1) density-dependent nest destruction occurs, but (2) it promotes a density-dependent feminization of hatchling sex ratio, and consequently (3) the global production of juveniles continues to increase in relation with the increasing number of deposited nests even for the highest densities observed at that beach. Mean annual production of female hatchlings per adult female, although density dependent, is less than two juveniles even at the lowest densities of nesting females.