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Recovery Strategy for the Northern and Southern Resident Killer Whale

1.  Background

1.1 Species Information

The status report and assessment summary for resident killer whales is available from the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) Secretariat (www.COSEWIC.gc.ca).

COSEWIC Assessment Summary

Common Name: killer whale, orca,

Scientific Name: Orcinus orca

Assessment Summary: Assessed in 1999, reviewed and revised in 2001

COSEWIC Status: 'Southern resident' killer whales are designated as endangered, 'northern resident' killer whales as threatened

SARA Status: 'Southern resident' killer whales, endangered, on Schedule 1 'Northern resident' killer whales, threatened on Schedule 1

Reason for Designation: The southern resident killer whale population is small, with recent declines of 17% between 1995 and 2001, and currently contains 85 members. The northern resident killer whale population is small at 205 members, with recent declines of 7% between 1997 and 2003. Seasonally, they are exposed to high levels of boat traffic. The availability of their prey is reduced relative to historic levels. High levels of persistent organic pollutants may be compromising their reproductive and immune systems, leading to reduced calving and/ or increased mortality rates.

Range in Canada: Pacific Ocean

Status History: In April 1999, the two North Pacific ‘resident’ killer whale populations were designated threatened.  In November 2001, the southern resident population was designated endangered while the northern resident population remained threatened.

1.1.1    Species Description

The killer whale is the largest member of the dolphin family, Delphinidae.  Its size, striking black and white colouring and tall dorsal fin are the main identifying characteristics.  Killer whales are mainly black above and white below, with a white oval eye patch, and a grey saddle patch below the dorsal fin.  Each killer whale has a uniquely shaped dorsal fin and saddle patch, and most animals have naturally acquired nicks and scars.  Individual killer whales are identified using photographs of the dorsal fin, saddle patch, and sometimes eye patches (Ford et al. 2000).  They are sexually dimorphic.  Maximum recorded lengths and weights for male killer whales are 9.0 m, and 5,568 kg respectively, whereas females are smaller at 7.7 m and 4,000 kg (Dahlheim and Heyning 1999).  The tall triangular dorsal fin of adult males is often as high as 1.8 m, while in juveniles and adult females it reaches 0.9 m or less.  In adult males, the paddle-shaped pectoral fins and tail flukes are longer and broader and the fluke tips curl downward (Bigg et al. 1987).

Currently, most authorities consider killer whales to be one species, Orcinus orca, having regional variations in diet, size, colouration, and vocal patterns (Heyning and Dahlheim 1988, Ford et al. 2000, Barrett-Lennard and Ellis 2001).  Two and possibly three distinct species have recently been proposed for Antarctic populations (Mikhalev et al. 1981, Berzin and Vladimorov 1983, Pitman and Ensor 2003), but they are not currently widely accepted (Reeves et al. 2004).  In addition, recent genetic studies report little global variation in mitochondrial DNA suggesting that the population segregation indicated by the morphological differences described above is relatively recent (Barrett-Lennard 2000, Hoelzel et al. 2002).

Three distinct forms, or ecotypes, of killer whale inhabit Canadian Pacific waters: transient, offshore and resident.  These forms are sympatric but socially isolated and differ in their dietary preferences, genetics, morphology and behaviour (Ford et al. 1998, 2000, Barrett-Lennard and Ellis 2001).  Transient killer whales feed on marine mammals; particularly harbour seals (Phoca vitulina), porpoises, and sea lions (Ford et al. 1998).  They travel in small, acoustically quiet groups that rely on stealth to find their prey (Ford and Ellis 1999).  To the experienced eye, the dorsal fins of transient whales tend to be pointed and their saddle patches are large and uniformly grey (Ford et al. 2000).  Offshore killer whales are not as well understood as residents and transients, but they are thought to feed on fish (Ford et al. 2000, Heise et al. 2003).  They travel in large acoustically active groups of 30 or more whales, using frequent echolocation and social calls (Ford et al. 2000).  The dorsal fins of offshore killer whales are more rounded than those of transients, and their saddle patches may either be uniformly grey or may contain a black region.

Resident killer whales are the best understood of the three ecotypes.  They feed exclusively on fish and cephalopods and travel in acoustically active groups of 10 to 25 or more whales (Ford et al. 2000).  The tips of their dorsal fins tend to be rounded at the leading edge and have a fairly abrupt angle at the trailing edge.  Their saddle patches may be uniformly grey or contain a black region.  The social organization of resident killer whales is highly structured.  Their fundamental unit is the matriline, comprising all surviving members of a female lineage.  A typical matriline comprises an adult female, her offspring, and the offspring of her daughters.  Both sexes remain within their natal matriline for life (Bigg et al. 1990).  Social systems in which both sexes remain with their mother for life has only been described in one other mammalian species, the long-finned pilot whale (Globicephala melas) (Amos et al. 1993).  Bigg et al (1990) defined pods as groups of closely related matrilines that travel, forage, socialize and rest with each other at least 50% of the time, and predicted that pods, like matrilines, would be stable over many generations.  However, Ford and Ellis (2002) showed that inter-matriline association patterns in the northern residents have evolved over the past decade such that some of the pods identified by Bigg et al. now fail to meet the 50% criterion.  Their analysis suggests that pods are best defined as transitional groupings that reflect the relatedness of recently diverged matrilines. 

Each resident pod has a unique dialect made up of approximately a dozen discrete calls (Ford 1989, 1991).  These dialects can be distinguished, providing each pod with a unique acoustic signature.  Dialects are probably learned from mothers and other associated kin and are highly stable over time (Ford et al. 2000).  Their function is not entirely understood, although it appears that they play an important role in mate selection (Barrett-Lennard 2000, discussed below in Section 1.4.1. Culture).  Despite having distinct dialects, some pods share certain calls and call variants. Pods that share one or more calls belong to a common clan.

Resident killer whales that share a common range and that associate at least occasionally are considered to be members of the same community or population.  There are two communities of resident killer whales in British Columbia, the northern residents and the southern residents.  They have not been observed interacting and genetic studies have revealed that the two populations rarely if ever interbreed (Barrett-Lennard and Ellis 2001).  The northern resident community consists of three clans, and the southern resident community consists of one.

The existence of two distinct populations of resident killer whales using the waters of Washington and British Columbia has been recognized by both the Canadian and US governments.  In 2001 COSEWIC assigned northern residents ‘threatened’ status, and southern residents ‘endangered’ status.  In the United States, marine mammals are afforded federal protection under both the Marine Mammal Protection Act (MMPA) and, when listed, under the Endangered Species Act (ESA).  The southern residents were listed as ‘depleted’ under the MMPA in 2003.  In February 2006, southern resident killer whales were listed as endangered under the ESA. In June 2004, the Washington State Department of Fish and Wildlife added southern resident killer whales to their endangered species list.

1.2 Distribution

1.2.1 Gobal Range 

Killer whales are found in all oceans, and are most common in areas associated with high ocean productivity in mid to high latitudes (Forney and Wade in press). They are able to tolerate temperatures ranging from those found in polar waters to the tropics, and have been recorded in water ranging from shallow (several metres) to open ocean depths (Baird 2001). 

1.2.2 Canadian Pacific Range 

Killer whales are found in all three of Canada's oceans, as well as occasionally in Hudson Bay and in the Gulf of St. Lawrence, but they appear to be uncommon in the Atlantic and the Arctic (COSEWIC 2003).  In British Columbia (BC), they have been recorded throughout almost all salt-water areas, including many long inlets, narrow channels and deep embayments (Baird 2001).  The three ecotypes of BC killer whales (offshore, transient, and resident) do not appear to interact socially despite their overlapping ranges (Ford et al. 2000).  Offshore killer whales are most often sighted on the continental shelf off the outer coast, but they are occasionally found in protected inside waters (Ford et al. 2000).  Transient killer whales range throughout the area, as do resident killer whales (Ford and Ellis 1999, Ford et al. 2000).   Residents and transients have occasionally been seen in close proximity to each other, but rarely interact (Ford and Ellis 1999).  Figure 1 shows many place names mentioned in the text, as well as the general ranges of northern and southern residents.

Figure1: The coast of British Columbia and northwest Washington State showing the general ranges of northern and southern resident killer whales

Figure 1: The coast of British Columbia and northwest Washington State showing the general ranges of northern and southern resident killer whales

The community of southern residents comprises a single acoustic clan, J clan, which is composed of three pods (referred to as J, K, and L) containing a total of 20 matrilines (Ford et al. 2000).  The known range of this community is from northern British Columbia to central California (Ford et al. 2000; unpublished data, Cetacean Research Program, Fisheries & Oceans Canada, Pacific Biological Station, Nanaimo, BC [CRP-DFO]).  During summer, its members are usually found in waters off southern Vancouver Island and northern Washington State, where they congregate to intercept migratory salmon.  The main area of concentration for southern residents is Haro Strait and vicinity off southeastern Vancouver Island (Figure 1), but they are commonly seen in Juan de Fuca Strait, and the southern Strait of Georgia (Ford et al. 2000).  Of the three southern resident pods, J pod is most commonly seen in inside waters throughout the year, and appears to seldom leave the Strait of Georgia-Puget Sound-Strait of Juan de Fuca region (Ford et al. 2000).  K and L pods are more often found in western Juan de Fuca Strait and off the outer coasts of Washington State and Vancouver Island.  Unlike J pod, K and L pods typically leave inshore waters in winter and return in May or June.  Their range during this period is poorly known, but they have been sighted as far south as Monterey Bay, California and as far north as Langara Island, off Haida Gwaii (Ford et al. 2000, Black et al. 2001, unpublished data (CRP-DFO). 

Northern Residents

The northern resident killer whale community comprises three acoustic clans (A, G, and R) containing 34 matrilines, which range from Glacier Bay, Alaska to Grays Harbour, Washington (Ford et al. 2000, unpublished data CRP-DFO).  From June to October, they frequent areas from mid Vancouver Island to southeastern Alaska, particularly Johnstone Strait and Queen Charlotte Strait (Figure 1), off northeastern Vancouver Island (Ford et al. 2000).  Their range at other times of the year is poorly understood. Small groups of northern residents are sometimes seen in Johnstone Strait and other inshore waters along the BC coast in winter (Ford et al. 2000) but such sightings are rare even when seasonal changes in observer effort are taken into account.

There is no evidence that clans are restricted to specific regions within the range of their community, but some show an apparent preference for particular areas (Ford et al. 2000).  For example, the most commonly sighted whales off northeastern Vancouver Island belong to A-clan, whereas most of the whales sighted off the west coast of Vancouver Island belong to G-clan, and R-clan seems to prefer the northern part of the community’s range.  The range of northern residents overlaps with southern residents and with a community referred to as the southern Alaskan residents.  Northern residents have never been seen associating with members of the southern resident community, and while they were observed travelling in proximity to a southern Alaskan resident pod on one occasion (Dahlheim et al. 1997), it is not clear that social mixing took place.  Genetic studies have not ruled out the possibility of occasional breeding between the northern resident and southern Alaskan resident communities (Barrett-Lennard and Ellis 2001).