Harbour porpoise (Pacific Ocean population) COSEWIC assessment and status report: chapter 6
Special Significance of the Species
As noted, harbour porpoises are the most common stranded cetacean in the province of British Columbia. Pollutant-ratio information, radio-tracking studies, and their year-round presence in the province implies that harbour porpoise have fairly limited ranges. Of all the cetaceans in the province, harbour porpoise appear to most consistently inhabit shallow, usually near-shore habitats. These features likely result in prolonged exposure to anthropogenic influences. For these reasons, of all the species of cetaceans in the province, they are the best candidate for an index species for programs monitoring the status of the marine environment (Baird 1994).
In southern British Columbia (and adjacent waters of Washington State) harbour porpoise are known to hybridize with Dall’s porpoise (Baird et al. 1998; Willis 2001). This is only the second species-pair of cetaceans world-wide where hybridization is known to regularly occur in the wild. Willis et al. (2004) notes that “natural hybridization events among other mammalian species almost always involve disturbed habitats where one population is in decline (e.g. Carr et al. 1986, Lehman et al. 1991)”.