Most porpoises are shy little animals that surface quietly, roll once and disappear. Dall’s porpoise is the exception. It is the heaviest member of the porpoise family, it is strikingly marked in black and white, and it travels at speeds that leave most boats behind. People who see one for the first time in Alaska, British Columbia or off the Pacific Northwest often report a “baby orca”. It isn’t one, and the differences are easy to learn once you know where to look. This page covers how to tell a Dall’s porpoise from a killer whale, how fast it really is, what it eats, where it lives and how it is doing. For the rest of the family, see our guide to all seven porpoise species.

Dall’s porpoise vs orca: how to tell them apart

The colour pattern is similar, but size, shape and behaviour separate them in seconds.

The confusion is understandable. Both animals are glossy black with a large white patch on the flanks and belly, and both live in the same cold North Pacific waters. But the resemblance is skin deep. A killer whale is the largest member of the dolphin family. Adult males reach 8 to 9 metres and carry a dorsal fin that can stand nearly 2 metres tall. Even a newborn orca calf is around 2 to 2.5 metres long, about the size of a fully grown Dall’s porpoise, and it never travels alone.

A Dall’s porpoise is a compact, almost torpedo-shaped animal with a very small head and no obvious beak. Its triangular dorsal fin is short, and the upper part of the fin, as well as the trailing edge of the tail flukes, is often frosted white or grey. Orcas have no white on the dorsal fin; instead they have a grey “saddle patch” behind it and a distinctive white oval patch behind each eye. Dall’s porpoise lacks the eye patch entirely.

Behaviour gives the game away too. Orcas surface with a slow, rolling motion and a tall blow. Dall’s porpoises tend to dash, and when they are moving fast they create a V-shaped plume of water off the head called a rooster tail. They also love to ride the bow wave of fast-moving boats, zigzagging back and forth under the bow, something adult orcas rarely do.

There is one more twist in the relationship: killer whales eat Dall’s porpoises. Mammal-hunting “transient” or Bigg’s killer whales in the eastern North Pacific take them regularly, and a porpoise’s best defence is its speed. So when you see the two together, it is usually not a family outing. For the basics of why these are different animals at all, see the difference between a dolphin and a porpoise.

How fast is a Dall’s porpoise?

Dall’s porpoise is often called the fastest porpoise and one of the fastest small whales of any kind. Burst speeds of around 55 km/h (about 34 mph) are commonly cited, though it can only hold that for short sprints. At cruising speed it moves much more slowly, often just a few kilometres an hour while it rests or forages.

The body is built for speed. It is thick and muscular through the middle, with a very deep tail stock and a narrow head that cuts through the water cleanly. When a Dall’s porpoise surfaces at high speed it barely clears the water, breathing in a fraction of a second while a sheet of spray peels off its head. That rooster tail is so distinctive that experienced observers can often identify the species from the splash alone, before they ever see the animal. For how it compares with orcas, sailfish and other speedsters, see what’s the fastest animal in the ocean.

Appearance and the two colour forms

Adult Dall’s porpoises are usually 1.8 to 2.4 metres long, with males slightly larger and noticeably thicker through the tail stock. Older males can develop a pronounced hump in front of the tail and a forward-canted dorsal fin. The skin is jet black except for a white flank patch that wraps under the belly, plus the frosted edges on the dorsal fin and flukes.

Scientists recognise two main colour forms. The common dalli-type, found across most of the range, has a white flank patch that starts roughly level with the dorsal fin. The truei-type, found mostly in the western North Pacific off Japan, has a much larger white patch that extends forward almost to the flipper. The two forms are treated as the same species, though they differ in where they breed. Occasional all-black and all-white individuals have also been reported.

Like other porpoises, Dall’s porpoise has tiny spade-shaped teeth, some of the smallest of any toothed whale. Between them, the gums carry hard bumps sometimes called “gum teeth” that help grip slippery prey.

Where Dall’s porpoises live

Dall’s porpoise is found only in the North Pacific and its adjoining seas: the Sea of Japan, the Sea of Okhotsk and the Bering Sea. In the east, it ranges from the Bering Sea and Gulf of Alaska down through British Columbia, Washington and Oregon to California, reaching as far south as Baja California in cold years. In the west, it occurs off Japan, Russia and the Kuril and Aleutian Islands.

Unlike the harbor porpoise, which hugs coastlines and bays, Dall’s porpoise is an animal of deeper, colder water. It is most common over the continental shelf edge and slope and in offshore waters, although it also enters deep inland passages such as Puget Sound, the Strait of Juan de Fuca, Johnstone Strait and Alaska’s Inside Passage. It prefers water below about 17°C. In some areas, especially British Columbia, Dall’s and harbor porpoises overlap, and the two species have even been documented hybridising. Our where do porpoises live page maps the ranges of every species.

What Dall’s porpoises eat

Dall’s porpoises feed mainly on small mid-water and deep-water fish and squid. Lanternfish are an important prey in many areas, along with hake, capelin, herring, pollock, mackerel and a variety of small squid. They can dive to several hundred metres, and they often feed at night, when the deep-scattering layer of lanternfish and squid rises toward the surface.

Like all porpoises, they need a lot of food for their size. A fast, warm-bodied animal living in cold water burns energy quickly, and estimates suggest Dall’s porpoises eat around a tenth of their body weight a day. They find prey with high-frequency echolocation clicks, a trait shared by the whole porpoise family. For more on diet across the family, see what do porpoises eat.

Behaviour, groups and breeding

Dall’s porpoises usually travel in small groups of two to ten animals, although larger, loose aggregations of hundreds or even thousands have been reported in rich feeding areas. They are active and sociable, and unlike most porpoises they actively approach boats to bow-ride. They are less keen on slow vessels; bow-riding usually happens when a boat is moving at a good clip, which gives them a pressure wave to surf.

Calves are born after a pregnancy of about 10 to 12 months, mostly in summer. Newborns are around a metre long. Females can breed every year or so, and in the western Pacific the two colour forms appear to calve in separate areas. Dall’s porpoises live up to about 15 to 20 years. Their main natural predators are killer whales and, less often, large sharks.

Threats and conservation status

Dall’s porpoise is one of the most abundant porpoises in the world, with a total population probably well over a million animals, and the IUCN lists it as Least Concern. That doesn’t mean it is free of problems. The biggest direct threat has been a hand-harpoon hunt off Japan, which in the late 1980s killed more Dall’s porpoises each year than any other directed hunt of a small cetacean anywhere. Catch quotas have since been reduced, but the hunt continues on a smaller scale, and scientists have long been concerned about its effect on local populations.

Dall’s porpoises also drown as bycatch in gillnets and driftnets. The high-seas driftnet fisheries of the North Pacific killed large numbers until a United Nations moratorium on large-scale driftnets took effect in the early 1990s. Other pressures include noise, pollution and shifts in prey linked to warming water. In US waters, the species is protected under the Marine Mammal Protection Act, and NOAA Fisheries tracks separate Alaska and California/Oregon/Washington stocks.

Dall’s porpoises have rarely been kept in captivity, and attempts in the past generally ended quickly. They are fast, wide-ranging animals that do poorly in tanks, which is one reason most of what we know comes from field studies, stranded animals and boat surveys.

What I’d look for if I were trying to spot one

The cold North Pacific is outside the dive trips I’ve written up on this site, so this is how I’d approach it rather than a story from the water. If I were on a ferry or whale-watching boat in Alaska or British Columbia, I’d watch the water ahead of the bow rather than looking for blows in the distance. A Dall’s porpoise announces itself with that spray of water, a fast white splash that looks almost like a skipping stone. If the animal is the size of a person, has white on its dorsal fin and no white eye patch, it’s a porpoise, not an orca calf.

From years of watching fish in my reef systems, I’ve learned that body shape tells you how an animal makes its living, and Dall’s porpoise is a good example. That thick, muscular tail stock is the same design you see in fast-swimming fish like tunas: a short, powerful engine at the back of a streamlined body. It’s built for bursts of speed and long days of hunting in open water, which is exactly the life it leads. If you want to see the rest of the family, start with the is a porpoise a whale? page for how porpoises fit into the whale family tree.