Abstract
Foraging specialization has been studied at both the group level and the individual level in marine mammals, including Indo-Pacific bottlenose dolphins (Tursiops aduncus) in Shark Bay, Western Australia. Specialization can be observed through direct or indirect observation of feeding tactics or studies of habitat use and habitat selection -- the disproportionate use of certain habitats. Here we examine habitat use and selection in male dolphin alliances, using date collected on 12 2nd -order alliances and five lone trios (120 individuals) over a six-year period (2001-2006). Using selection ratios, we assessed selection of five habitats (Shallows, Channels, Offshore Banks, Embayment, and Intermediate) at two different levels: with respect to proportion of habitats available to all animals and within alliance specific home ranges. We found that with respect to habitat available across the study area, all alliances were selective with respect to foraging habitat. Within their respective home ranges, seven alliances showed significant selection of foraging habitat deviating from expected. We compared habitat selectivity between alliances with overlapping home ranges and found that while some alliances were not selective about foraging habitats within their home range, others foraged disproportionately in certain habitats. Eigenanalysis of selection ratios also showed this variation in selection of foraging habitat between overlapping alliances. Previous studies on foraging specialization in this population have focused on females; however our results indicate the presence of foraging specialization in males as well. This raises the possibility that the considerable variation in alliance size in this population may be influenced by the distribution of food as well as females.