Changes in dive patterns of leatherback turtles with sea surface temperature and potential foraging habitats

Marine mesotherms are able to occupy broader thermal niches than
ectotherms; however, this means they must exhibit greater tolerance to
diverse environmental conditions across the ocean. Knowledge remains
limited about how differences in environmental conditions within occupied
habitats affect the bioenergetics of mesotherms and associated ecological
traits. Here, we report that leatherback turtles (Dermochelys coriacea)
migrating across the North Pacific changed their dive behavior regionally,
possibly in response to changes in sea surface temperature and prey
abundance. Our results demonstrate that dives became deeper when the
surface water was warmer, presumably because leatherbacks dive to deep
cold waters to avoid overheating. Moreover, the patterns of
presumed foraging dives indicate that leatherbacks engage in behavioral
thermoregulation in warmer foraging regions, which perhaps limit the time
available for foraging activity. In contrast, mesothermy allows
leatherbacks to spend more time foraging in cool-temperate regions.
However, it might not produce greater reproductive output due to
additional migration cost to these areas, which are more distant from
their nesting beaches. Our results highlight that mesothermy might not
provide a direct fitness advantage to all individual leatherback turtles;
rather, it affords a species-level fitness advantage by allowing a greater
diversity of habitats to be utilized.