The Dall’s porpoise is a widespread and numerous species in the North Pacific, and yet much is to be learned about the species. It lives along the coast and in the open ocean from California to Japan. It prefers deep canyons in coastal areas and where water is cold. It is likely that these places have the greatest prey abundance.

Adult porpoises are mostly black in colour with white flanks and white tipped fins. Young porpoises are grey with white flanks. Reeves et al.’s (2002) book has excellent illustrations of age classes. Two types of Dall’s porpoise occur - the truei type is found in the western Pacific off Japan and the dalli type along the Pacific Coast of North America. The western Pacific form has a white lateral patch extending to the pectoral fins whereas the white lateral line on the dalli type reaches only to the mid line of the dorsal fin.

Estimating the number of Dall’s porpoises is difficult because of their wide ocean going range. Estimates range from several hundred thousand to 1 million animals but there is not much certainty in these estimates. Dall’s porpoise is often attracted to moving boats to ride the bow wave and schools of 2 to 12 animals are most common.

Calves are born in June and July, and mating occurs soon after the calves are born. Calves stay with their mothers until the next calf is born. They then gather with other immature porpoises and adult males in the southern part of the range. Dall’s porpoises eat deepwater fish and squid probably at night, and schooling fish such as herring, anchovy, hake and juvenile rockfish during the day. Orcas and sharks prey on porpoises. There are excellent photographs of orcas hunting porpoises on page 19 in Ford et al. (2000) and page 473 in Reeves et al. (2002). Baird et al. (1998) reported the first hybridization for the species. They found a 60-cm female fetus in a dead Dall's porpoise in southern British Columbia that was fathered by a harbour porpoise (Phocoena phocoena).