Dispersal and Diving Adjustments of the Green Turtle Chelonia mydas in Response to Dynamic Environmental Conditions during Post-Nesting Migration
Abstract
In response to seasonality and spatial segregation of resources, sea turtles undertake long
journeys between their nesting sites and foraging grounds. While satellite tracking has
made it possible to outline their migration routes, we still have little knowledge of how they
select their foraging grounds and adapt their migration to dynamic environmental conditions.
Here, we analyzed the trajectories and diving behavior of 19 adult green turtles (Chelonia
mydas) during their post-nesting migration from French Guiana and Suriname to their
foraging grounds off the coast of Brazil. First Passage Time analysis was used to identify
foraging areas located off Ceará state of Brazil, where the associated habitat corresponds
to favorable conditions for seagrass growth, i.e. clear and shallow waters. The dispersal
and diving patterns of the turtles revealed several behavioral adaptations to the strong
hydrodynamic processes induced by both the North Brazil current and the Amazon River
plume. All green turtles migrated south-eastward after the nesting season, confirming that
they coped with the strong counter North Brazil current by using a tight corridor close to the
shore. The time spent within the Amazon plume also altered the location of their feeding
habitats as the longer individuals stayed within the plume, the sooner they initiated foraging.
The green turtles performed deeper and shorter dives while crossing the mouth of the Amazon,
a strategy which would help turtles avoid the most turbulent upper surface layers of the
plume. These adjustments reveal the remarkable plasticity of this green turtle population
when reducing energy costs induced by migration.
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Environmental SciencesOrigin | Publisher files allowed on an open archive |
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