Characterization of postdive recovery using sound recordings and its relationship to dive duration, exertion, and foraging effort of southern elephant seals (Mirounga leonina)
Résumé
It is notoriously difficult to measure physiological parameters in cryptic free-ranging
marine mammals. However, it is critical to understand how marine mammals
manage their energy expenditure and their diving behavior in environments where
the predation risks are low and where survival is mainly linked to capacities to maintain
physiological homeostasis and energy budget balance. Elephant seals are top
marine predators that dive deeply and continuously when at sea. Using acoustic
recorders deployed on two postbreeding southern elephant seals (SES) females, we
developed methods to automatically estimate breathing frequency at the surface.
Using this method, we found that seals took successive identical breaths at high frequency
(0.29 Hz) when recovering at the surface and that breath count was strongly
related to postdive surfacing time. In addition, dive depth was the main factor
explaining surfacing time through the effects of dive duration and total underwater
swimming effort exerted. Finally, we found that recovery does not only occur over
one dive timescale, but over a multidive time scale for one individual. The way these
predators manage their recovery will determine how they respond to the change in
oceanic water column structure in the future.