Dall’s Porpoise (Phocoenoides dalli)

Quick facts

only found in the North Pacific Ocean
this is the most commonly seen porpoise in the Victoria area
very social and playful, they will often “surf” in the bow (front) wake of boats
their crisp, high contrast black & white colour
mis-identification as baby killer whales from shore-based onlookers because of colouration
adults generally 2 m (5–6 ft ) long
calves about 90 cm (3 ft ) long at birth
fastest marine mammal in the world
feed on small schooling fish and squid by herding them like cattle

Description

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. The Dall’s porpoise looks and acts like a little black and white torpedo. Fully grown, it is only slightly more than two metres (6.6 ft) long, but it is stocky and powerfully built, weighing about 220 kilograms (484 lbs). 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 coloring 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 gray 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 and habitat

Dall’s porpoises are likely the most common small cetaceans 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. The Dall’s porpoise is one of the fastest swimmers on the BC 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.

Reproduction

Dall’s porpoises most often travel in groups of five or less. Births can take place at any time of year, but seem to peak in spring and summer. Calves are about one metre long (3.3 ft) 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.

Feeding behaviour

The Dall’s porpoise eats 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.

Comments

The Dall’s porpoise is widely distributed in the North Pacific, where there are an estimated 1.4 to 2.8 million. It’s common in BC 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.