Characterizing the socially transmitted foraging tactic "sponging" by bottlenose dolphins (Tursiops sp.) in the western gulf of Shark Bay, Western Australia

Individual foraging tactics are widespread in animals and have ecological and evolutionary implications. Indo-Pacific bottlenose dolphins (Tursiops sp.) in Shark Bay, Western Australia, exhibit a foraging tactic involving tool use, called "sponging." Sponging is vertically, socially transmitted through the matriline and, to date, has been described in detail in the eastern gulf of Shark Bay (ESB). Here, we characterize sponging in the western gulf of Shark Bay (WSB), in which a different matriline engages in the behavior. We identified 40 individual "spongers" in 9 mo of boat-based surveys over three field seasons. As is the case in ESB, the majority of WSB spongers was female and engaged in sponging in deep channel habitats. In contrast to ESB, however, there was no difference in the number of associates between spongers and nonspongers in WSB, and activity budgets differed between spongers and deep-water nonspongers; spongers foraged more frequently and rested less than nonspongers. Group sizes in deep channel habitat, where sponging was prevalent, were typically larger than those in shallow habitat, except for foraging, perhaps indicative of higher predator abundance and/or scattered prey distribution in deep-water habitat. This research improves our understanding of within-population foraging variations in bottlenose dolphins.