The following information is part of the text from the report "Status of killer whales in Canada" by R.W. Baird
Special Significance
Among the cetaceans, killer whales exhibit several unusual features related to social organization and behaviour. One is the presence of the two sympatric populations (residents and transients) in the nearshore waters of the eastern North Pacific, each specializing on different prey types, and differing in behaviour, acoustics, and morphology (Baird and Stacey 1988; Bain 1989; Ford and Hubbard-Morton 1989; Morton 1990). Such a situation, with foraging specializations occurring among sympatric populations, is unusual for mammals, as well as for vertebrates in general (see Mayr 1996, Otte and Endler 1989). This system may provide valuable information on the causes and consequences of reproductive isolation between populations (Baird 1994).
One apparent consequence of the differences in diet between the two forms are differences in dispersal patterns. For residents no dispersal of either sex occurs; individuals travel in long-term stable groups comprised of several maternal lineages. This situation has not been documented for any other population of cetacean, or any other species of non-human mammal. For transients, dispersal of most individuals of both sexes from the maternal group occurs, though not all male offspring seem to disperse (Baird 1994, 1995b, 1999; Baird and Whitehead 1998). Such variability in dispersal patterns between sympatric populations of closely related animals provides a unique opportunity for examining some of the costs and benefits of group living.
The types of foraging specialization found in populations in the eastern North Pacific may also occur elsewhere in the world, though research efforts elsewhere have been generally insufficient to determine whether sympatric forms specializing on different prey types exist. Individuals of some populations feed almost exclusively on other marine mammals. Such predation on marine mammals makes the study of foraging behaviour easier than perhaps for any other species of cetacean. Several interesting findings have come from these studies, including evidence that females teach hunting skills to their offspring (Lopez and Lopez 1985; Guinet 1991b; Guinet and Bouvier 1995), and also a strong relationship between group size and foraging success in one population (Baird and Dill 1996).
Besides these intrinsic characteristics, killer whales also hold an unusual fascination for humans. Such fascination is reflected in the large attendance figures at aquaria which hold killer whales around the world, through the demand for commercial excursions to see these animals in the wild, and through the large number of popular books, magazine articles and films which have been devoted towards these animals. In the Haro Strait region, a trans-boundary area between Washington state and British Columbia, a large and growing whale watching industry focused on this species exists (Baird et al. 1998b; Figure 6). Ticket sales for this area (in both the U.S. and Canada combined) were estimated to be approximately 5.5 million (U.S.) dollars in 1997 (R.W. Osborne, personal communication).
Evaluation
The taxon Orcinus has been evaluated by the IUCN Cetacean Specialist Group, and designated as Lower Risk: Conservation Dependent (IUCN 1996). This category, effectively one level below the IUCN Vulnerable category (which includes species facing a high risk of extinction in the wild in the medium-term future), includes species which are the focus of a continuing conservation program, the cessation of which would result in qualifying for one of the higher (e.g., Vulnerable) categories within a period of five years (IUCN 1996). The COSEWIC Fish and Marine Mammal Subcommittee classification of "Endangered" is for species "facing imminent extirpation or extinction", "Threatened" is for species that are "likely to become endangered if limiting factors are not reversed", and "Vulnerable" is for those species "of special concern because of characteristics which make [them] particularly sensitive to human activities or natural events" (Campbell 1996). The COSEWIC definition of "species" is particularly important in evaluation of the status of killer whales, as it explicitly includes any "subspecies, variety or geographically defined population[s]". Evidence is summarized below regarding killer whale populations in Canada relevant to such classification.
Off the British Columbia coast, killer whales are subdivided into a number of populations, and these populations are distinct genetically, morphologically, and behaviourally (see e.g., Table 1). Based both on these biological characteristics and the COSEWIC "species" definition, it is clear that these populations warrant independent evaluation and classification, where appropriate (it should also be noted that these populations are evaluated and listed independently in the U.S. - Barlow et al. 1997; Hill et al. 1997). One of the B.C. populations, the "northern" residents, has been growing since the end of live-capture fisheries in the early 1970s, but the population in British Columbia only numbers just over 200 individuals. The "southern" residents have not shown a steady increase, and the population size has declined by 10% in the last three years (1996-1998), to a level below that prior to live-captures (Figure 5). This decline is due to an increase in mortality rate, particularly mortality of adult females. The cause or causes of this increase in mortality are unclear, but there are several possibilities (Table 3). The core area for southern residents (Haro Strait) is bounded by the cities of Vancouver, Victoria and Seattle, with over 5.5 million people living in the area, increasing numbers of commercial and recreational vessel traffic, and numerous sources of pollutants. It seems unlikely that either pollution of these waters or vessel traffic will decrease in the near future. Southern residents have toxic chemical levels three times higher than levels known to cause immunotoxicity in harbour seals, and the most immediate anthropogenic risk to these populations is likely immunotoxic effects from this accumulation of persistent toxic chemicals (see Ross et al. 1996a, 1996b, 1998). Potential impacts of a reduction in prey populations and increasing numbers of commercial and recreational whale watching boats (Figure 6) may also be serious threats, although insufficient information is available to evaluate the magnitude of these threats. In terms of reduction of salmon populations, numbers in the Strait of Georgia, where the southern residents spend a large proportion of their time, have been reduced to a larger extent than populations elsewhere in B.C. (Slaney et al. 1996).
For transient and "offshore" killer whales in B.C., no population trend information is available, though, as with both northern and southern residents, population sizes appear to be small. Transients feed high on the food web, and are likely also at risk from high levels of contamination by persistent toxins. For killer whales in the Canadian Arctic and Atlantic, no information on population identity or trends is available, though populations appear to be very small, and the threats which face British Columbia populations likely also impact eastern Canadian and Arctic populations. Because of their small population sizes (in the low hundreds), killer whales are also at risk from natural events (e.g., entrapment or mass stranding) which could drastically impact a local population.
From the above, it is clear that all populations of killer whales in Canadian waters should, at the minimum, be classified as Vulnerable by COSEWIC. The only question that remains is whether one of the populations, the southern residents, should be classified as Threatened. The population is extremely small (89 individuals in 1998), has declined by 10% in three years due to an increase in mortality rates, and several threats have been identified which have the potential to cause this population to become "Endangered". As noted, it is unlikely that at least some of these threats (pollutants, vessel traffic) will be reversed in the foreseeable future. While it is unclear whether the recent (1996-1998) decline is directly due to these anthropogenic factors, or whether the population will continue to decrease, the rate at which this population has declined demonstrates how quickly such a population could become Endangered. That the threats to the population are insidious, difficult to quantify, and even harder to rectify, all warrant a conservative (precautionary) approach to management (see Richards and Maguire 1998). Without a Threatened classification, it seems unlikely that anything will be done regarding mitigation of these impacts, and the time frame for COSEWIC evaluation is slow enough (10 year evaluations for Vulnerable species) that the population could become Endangered well before another evaluation is undertaken. Since the population is a trans-boundary stock, efforts to coordinate actions with U.S. management agencies are also required.