A beluga whale calf is born dark grey, with sometimes a bluish or brownish tinge that gets lighter with age. It turns pure white between 5 to 12 years. The adult beluga whale sometimes has a yellowish tinge, caused by a layer of diatoms growing on it, although this colouration is lost during summer moulting – an unusual event for cetaceans. The body is robust and wrapped in a thick layer of blubber to protect it from arctic temperatures. This blubber often forms thick rubbery folds along the sides and belly. The animal has a short beak and large bulbous melon. The beluga can change the shape of its melon as well as the shape of its face to produce an amazing range of vocalizations. One of the most vocal cetaceans, belugas earned the name 'sea canary' from early mariners. Indeed, beluga vocalisations can often be heard above water and even through the hull of a boat. Belugas and Irrawaddy dolphins are the only cetaceans that can significantly alter their facial expressions with the lips appearing rounded when they are producing certain sounds. The neck vertebrae are not fused as they are in most other cetaceans, which gives them much greater flexibility. Instead of a dorsal fin the beluga has a low dorsal ridge. It has very thick tough skin, especially around the melon, which it can use to break through surface ice to breathe. The trailing edges of the flukes are convex, rather than concave like most other cetaceans and the trailing edges of the small rounded flippers curl upwards in males, whereas they remain flat in females.
The beluga or white whale has been well-studied. It has also been heavily exploited over past decades, hunted for food and captured for display. The bright white skin makes it easy to see in contrast to the dark ocean, but it also allows it to blend in with floating ice or whitecaps. This colouration also makes it hard to be confused with other species; only young narwhals might be mistaken for young belugas but the accompanying adult makes identification easy. The narwhal and the beluga together comprise the Monodontidae family.
Beluga whales can produce a wide range of sounds, and they have a sophisticated sonar system which they can use to manoeuvre in very shallow water. They can often survive stranding until the next tide comes in if they are not attacked by predators. They rarely breach, but often spyhop and lobtail, and show curiosity around boats. They are found in arctic and sub-arctic waters, both offshore and in coastal and estuarine waters. They sometimes travel hundreds of miles up rivers in summer months to reach calving grounds. Solitary individuals are increasingly reported for this species.
Beluga whales are distributed in high latitudes of the northern hemisphere from the west coast of Greenland westwards to Svalbard. Resident populations also occur in Cook Inlet (Alaska) and the St. Lawrence River system (Canada). Beluga whales have been hunted for centuries. Many are still hunted today for both food and for display in captive facilities. Natural predators include orca, and belugas sometimes become trapped in ice which may cause them to perish and can sometimes make them easy prey for polar bears. Human threats include oil and gas exploration and extraction, hydro-electrical developments, pollution, prey depletion, bycatch, and climate change. Some studies suggest that contaminants may cause increased disease and problems with immune system function and individuals residing in the Gulf of St. Lawrence have such high concentrations of chemical contaminants that they are treated as toxic waste when they die. The IWC currently recognises 29 management stocks of belugas. The IUCN currently lists the species' status as Near Threatened (2008), although the population of approximately 300 individuals in the Cook Inlet in Alaska is listed as Critically Endangered.