Dispersal and dive patterns during the post-nesting migration of olive ridley turtles from French Guiana

Behavioral plasticity allows migrating animals to adjust their migration patterns in relation to the environmental conditions they encounter during their movements. Sea turtles display long post-nesting migrations which vary considerably between species and populations. To date, there has been no description of migratory patterns of the large population of olive ridley turtles Lepidochelys olivacea in the west Atlantic. Here, we investigated dispersal and dive patterns in relation to environmental conditions of 7 satellite-tracked olive ridley females from French Guiana during their post-nesting migration. After they left the nesting beach, turtles followed a consistent northwestward direction and then remained in the restricted yet productive neritic domain of the continental shelf of French Guiana and Suriname. Despite this restricted dispersal range, turtles demonstrated variability in the habitats they exploited, i.e. the coastline, the continental shelf, and the continental slope, illustrating some plasticity. Moreover, turtles showed 2 different foraging strategies, either directly reaching a specific foraging area off river mouths, or meandering over the neritic area exploiting several foraging areas. In addition, turtles showed different dive patterns related to their habitat, although mostly exploiting the seabed by routinely performing U-shaped benthic dives. Overall, turtles vertically exploited non-stratified water masses characterized by warm surface temperatures consistent with their preferential thermal habitat. The migration strategy used by olive ridleys from French Guiana raises conservation concerns, since turtles may be exposed to coastal human-induced activities that must be considered in the implementation of accurate management measures for this still poorly studied population.