You Are What You Eat: Foraging Specializations and Their Influence on the Social Organization and Behavior of Killer Wha
The feeding ecology of predators can have a profound effect on their life history and behaviour. The killer whale—the apex marine predator—has a cosmopolitan distribution throughout the world’s oceans. Globally, it is a generalist predator with a diverse
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You Are What You Eat: Foraging Specializations and Their Influence on the Social Organization and Behavior of Killer Whales John K.B. Ford and Graeme M. Ellis
J.K.B. Ford (*) • G.M. Ellis Fisheries and Oceans Canada, Pacific Biological Station, Nanaimo, BC, Canada V9T 6N7 e-mail: [email protected] J. Yamagiwa and L. Karczmarski (eds.), Primates and Cetaceans: Field Research and Conservation of Complex Mammalian Societies, Primatology Monographs, DOI 10.1007/978-4-431-54523-1_4, © Springer Japan 2014
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Abstract The feeding ecology of predators can have a profound effect on their life history and behaviour. The killer whale—the apex marine predator—has a cosmopolitan distribution throughout the world’s oceans. Globally, it is a generalist predator with a diverse diet, but regionally, different socially and genetically isolated killer whale populations can have highly specialized foraging strategies involving only a few types of prey. In the eastern North Pacific, the three sympatric killer whale lineages have distinct dietary specializations: one feeds primarily on marine mammals, another on salmon, and the third appears to specialize on sharks. These ecological specializations are associated with distinct patterns of seasonal distribution, group size, social organization, foraging behavior, and acoustic activity. Divergent foraging strategies may have played a major role in the social isolation and genetic divergence of killer whale populations. Keywords Apex predator • Feeding ecology • Orcinus orca
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Introduction
Ecological specialization is an important factor promoting the evolution of biological diversity and speciation (Futuyma and Moreno 1988; Robinson et al. 1996; Dieckmann and Doebeli 1999; Schluter 2001; Via 2001). Optimal foraging theory predicts that selection will generally favor dietary specialization, as specialists have a competitive advantage over generalists in foraging efficiency (as in the adage, “the jack-of-all-trades is the master of none”) (Stephens and Krebs 1986; Futuyma and Moreno 1988; Robinson et al. 1996). Such selection may drive the divergent evolution of a wide variety of adaptive traits involving morphology, physiology, and behavior of populations or subpopulations with different foraging strategies or in contrasting environments. Divergent selection between sympatric populations may lead to assortative mating, reproductive isolation, and, ultimately, speciation (Dieckmann and Doebeli 1999; Schluter 2001; Via 2001; McKinnon et al. 2004). Killer whales, the largest of the dolphins (family Delphinidae), provide an exceptional opportunity to gain insight into the processes and outcomes of ecological specialization and divergence in a highly social and versatile mammalian predator. This species (only a single species, Orcinus orca, is currently recognized) is one of the most widely distributed mammals on the planet. It has a cosmopolitan distribution in all the world’s oceans, from the pack ice edges in both the Northern and Southern Hem
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