It is adapted to life in the Arctic, so has a number of anatomical and physiologicalcharacteristics that differentiate it from other cetaceans. Amongst these are its unmistakable all-white colour and the absence of a dorsal fin. It possesses a distinctive protuberance at the front of its head which houses an echolocation organ called the melon, which in this species is large and plastic (deformable). The beluga’s body size is between that of a dolphin’s and a true whale’s, with males growing up to 5.5 m (18 ft) long and weighing up to 1,600 kg (3,500 lb). This whale has a stocky body; it has the greatest percentage of blubber. Its sense of hearing is highly developed and it possesses echolocation, which allows it to move about and find blowholes under sheet ice.
Belugas are gregarious and they form groups of up to 10 animals on average, although during the summer months, they can gather in the hundreds or even thousands in estuaries and shallow coastal areas. They are slow swimmers, but they can dive down to 700 m (2,300 ft) below the surface. They are opportunistic feedersand their diets vary according to their locations and the season. They mainly eat fish,crustaceans and other deep-sea invertebrates.
The majority of belugas live in the arctic and the seas and coasts around North America, Russia and Greenland; their worldwide population is thought to number around 150,000 individuals. They are migratory and the majority of groups spend thewinter around the arctic ice cap; but when the sea ice melts in summer, they move to warmer river estuaries and coastal areas. Some populations are sedentary and do not migrate over great distances during the year.