Acoustic and diving behavior of sperm whales (Physeter macrocephalus) during natural and depredation foraging in the Gulf of Alaska

Delphine Mathias (1) , Aaron Thode (1) , Jan Straley (2) , John Calambokidis (3) , Gregory S. Schorr (3) , Kendall Folkert (4)

1 SIO - UC San Diego - Scripps Institution of Oceanography
2 UAS - University of Alaska [Southeast]
3 Cascadia Research Collective
4 Chercheur indépendant

Sperm whales have depredated black cod (Anoplopoma fimbria) from demersal longlines in the Gulf of Alaska for decades, but the behavior has recently spread in intensity and geographic cover- age. Over a three-year period 11 bioacoustic tags were attached to adult sperm whales off Southeast Alaska during both natural and depredation foraging conditions. Measurements of the animals' dive profiles and their acoustic behavior under both behavioral modes were examined for statisti- cally significant differences. Two rough categories of depredation are identified: "deep" and "shallow." "Deep depredating" whales consistently surface within 500 m of a hauling fishing ves- sel, have maximum dive depths greater than 200m, and display significantly different acoustic behavior than naturally foraging whales, with shorter inter-click intervals, occasional bouts of high "creak" rates, and fewer dives without creaks. "Shallow depredating" whales conduct dives that are much shorter, shallower, and more acoustically active than both the natural and deep depredating behaviors, with median creak rates three times that of natural levels. These results suggest that dep- redation efforts might be measured remotely with passive acoustic monitoring at close ranges.

Domaines: Ecologie, Environnement

Delphine Mathias, Aaron Thode, Jan Straley, John Calambokidis, Gregory S. Schorr, et al.. Acoustic and diving behavior of sperm whales (Physeter macrocephalus) during natural and depredation foraging in the Gulf of Alaska. Journal of the Acoustical Society of America, 2012, pp.518-532. ⟨10.1121/1.4726005⟩. ⟨hal-00904056⟩