Naturespeak 

Killer whales: Culture, communication and conservation of West Coast Orcas

By John Ford, Marine Mammal Research Program, Conservation Biology Section, Pacific Biological Station, Fisheries and Oceans Canada, Nanaimo, B.C.

Although killer whales range throughout the world’s oceans, nowhere are they more frequently found, observed and studied than on Canada’s west coast. Once feared and persecuted, orcas are now a revered icon of the wild marine environment in British Columbia, and the focus of a multi-million dollar whale-watching industry. Killer whales have also been the focus of intensive scientific study. From this research, a remarkable story of an innovative, adaptable, highly social and communicative predator has emerged.

Our scientific understanding of killer whale life history began in the early 1970s, when Dr. Michael Bigg and his co-workers at the Pacific Biological Station on Vancouver Island began a long term study of killer whales. Mike Bigg developed an innovative field technique – he took photographs of nicks and scars on the whales’ dorsal fin and back and used these markings to identify each individual animal.

By 1975, Mike and his colleagues had discovered that the typical travelling group – known as a "pod" – is a stable collection of 10-20 related animals, including adult males and females, sub-adults, and young calves. A number of these pods were encountered frequently during the summer months in predictable locations, and thus Mike called them "resident pods." Occasionally, however, they would encounter small groups of unfamiliar whales, often in unusual locations outside the regular travel routes of the residents. These small groups never mixed with the larger resident pods and, thinking that they were perhaps social outcasts just passing through the range of the residents, Mike called them "transients."

In the 25 years that have passed since residents and transients were first recognized, ongoing field studies have revealed a most remarkable picture of these two forms of orcas. Rather than transients being outcasts or rejects from resident pods, the two are entirely distinct populations that exist in social isolation in the same waters. Residents and transients differ in striking ways – their social structure, range, genetic structure, vocal patterns, and especially their diet. These differences appear to represent cultural traditions and adaptations that have evolved over millennia, with the whales becoming increasingly specialized to entirely different hunting lifestyles.

The principal difference between residents and transients is their diet. Residents eat squid and fish, especially salmon, while transients evidently shun these types of prey in favour of marine mammals, such as seals and porpoises, and seabirds. This situation – where two separate populations of a single species occupy the same habitat and have such divergent food preferences – has never been observed in any other mammal.

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