Dall's porpoise
Phocoenoides dalli

The Dall’s porpoise is a speed demon, well-known to mariners on the British Columbia coast for its habit of riding the bow waves of passing boats.

Description

The Dall’s porpoise looks and acts like a little black and white torpedo. Fully grown, it is only slightly more than 2 metres long, but it is stocky and powerfully built, weighing about 220 kilograms. Its small head and short flippers make its body look even more torpedo-like. Its mouth is small and narrow, and like all porpoises, it does not have much of a snout, or beak.

Striking black and white colouring makes the Dall’s porpoise easy to recognize at close range. The body is shiny black except for a large white patch on the flanks and belly. The outer edges of the tail look like they’ve been dipped in white or gray paint. When seen from a distance, the Dall’s porpoise can be mistaken for its smaller cousin, the harbour porpoise. Their dorsal fins are both triangular, but the fin of the Dall’s is often frosted with white or grey on the tip. Sometimes, the Dall’s porpoise is even confused with its much larger, black and white relative, the killer whale. Many boaters unfamiliar with  Dall’s porpoises have reported a group of "baby killer whales" riding their bow wave.

Range

Dall’s porpoises are likely the most common small cetacean in the north Pacific. They can be seen year-round in coastal and offshore waters all along the B.C. coast, particularly where there are deep underwater channels and canyons. Boaters and ferry passengers often see small groups of Dall’s porpoises in the Straits of Georgia and Juan de Fuca, as well as Johnstone and Queen Charlotte Straits off northeastern Vancouver Island.

Behaviour

The Dall’s porpoise is one of the fastest swimmers on the B.C. coast. Often, the first view of a Dall’s is a v-shaped splash, made by its dorsal fin as it rockets through the water. Because of its shape, this splash is called a rooster tail. Dall’s are best known for riding the bow waves of boats, darting back and forth with lightning speed just below the surface. Despite their high energy, they almost never leap clear of the water. When they do travel slower, Dall’s porpoises can be hard to spot. A quick glimpse of their dorsal fins and small, black backs is usually the only sign they are there. 

Dall’s porpoises most often travel in groups of five or less. Births may take place at any time of year, but seem to peak in spring and summer. Calves are about 100 centimetres at birth and may stay with their mothers for up to two years. Very little else is known about the social life of Dall’s porpoises. Identifying individuals using photography is very difficult when the subject is so fast. 

The Dall’s porpoise likes to eat squid and small schooling fish, such as herring, capelin and eulachon. It uses it small teeth to capture its prey, which it usually swallows whole.

Status

The Dall’s porpoise is widely distributed in the north Pacific, where it is estimated there are 1.4 to 2.8 million. It is quite common in B.C. waters. Occasionally, Dall’s porpoises are accidentally caught in fishing nets. And, because they live in coastal waters, pollution is a concern. Fortunately, boat traffic seems to be an attraction rather than an annoyance to this lively and entertaining porpoise.