Beluga whale

Belugas live in the far north, where the sea is very cold.

They swim between chunks of ice. In summer they visit shallow bays and rivers.

Belugas live in the Arctic Ocean and the cold seas around it, near Alaska, Canada, Greenland, Russia and Norway. They swim among floating ice in near-freezing water.

In summer many belugas move into shallow bays and the mouths of big rivers to feed on fish and give birth. They come back to the same summer places year after year. In winter they move to deeper water near the edge of the ice.

Belugas have a discontinuous circumpolar distribution in Arctic and sub-Arctic waters, generally where the sea is ice-covered for part of the year. NOAA notes they are common in Alaska and in Russian, Canadian and Greenland waters; NAMMCO adds Norway's Svalbard.

Most populations are migratory, wintering among pack ice, leads and polynyas and summering in shallow bays and estuaries of large northern rivers. A few small populations, such as those of Cook Inlet in Alaska and the St. Lawrence Estuary in Canada, stay in one region year-round. Belugas show strong site fidelity, returning to their birth areas each summer.

A beluga has no fin on its back.

That helps it swim under ice. Thick fat keeps it warm. It can nod and turn its head!

Most whales and dolphins have a fin on their back, but belugas have only a tough ridge. That lets them swim close beneath sheets of floating ice. Their scientific name, Delphinapterus, means dolphin without a fin.

A thick layer of fat called blubber, up to 40 percent of their weight, keeps them warm and stores energy. Unlike most whales, a beluga can nod and turn its head, because the bones in its neck are not joined together. Each summer some belugas rub on gravel to scrub off old, yellowed skin.

Instead of a dorsal fin, belugas have a tough dorsal ridge, an adaptation for moving under ice floes. The cervical vertebrae are unfused, unlike those of most cetaceans, so the head can nod and turn, useful for scanning and foraging in shallow, complex habitats.

Blubber makes up as much as 40 percent of body weight, providing insulation and an energy store. Some populations molt each summer, rubbing against coarse gravel in shallow water to shed the outer skin layer. Vision is good both in and out of water, but hearing and echolocation are the main senses for navigating and hunting.

A baby beluga is called a calf.

It is born in summer, in warmer water. It drinks milk for at least two years. It stays close to its mother.

Belugas mate in late winter and spring. A mother is pregnant for a little over a year, about 14 to 15 months, and gives birth in summer in shallow, warmer water, because newborn calves do not yet have thick blubber.

Calves drink milk for at least two years. Females can have a calf every 2 to 3 years and start having babies when they are about 6 to 14 years old. Belugas can live a very long time: scientists count yearly layers in their teeth, like tree rings, to tell their age.

Mating takes place in late winter and spring; NOAA gives a pregnancy of about 15 months and NAMMCO 14 to 14.5. Calves are born in summer in relatively warm estuaries and tidal flats, nurse for at least two years, and females give birth every 2 to 3 years after maturing at about 6 to 14.

Age is estimated from growth layer groups deposited in the teeth each year. The oldest recorded beluga had 80 layers, probably an underestimate because teeth wear down, and NOAA gives a lifespan of up to about 90 years. Belugas are among the few mammals known to go through menopause, although one 70-year-old female in Alaska was found carrying a near-term calf.