What is a beluga?

Nicknamed “the canary of the sea” for the extraordinary richness of its vocalisations, the beluga (Delphinapterus leucas) is an Arctic cetacean of striking beauty and originality. Its spotless white skin, its remarkably mobile domed forehead and its surprising acoustic repertoire make it one of the most recognisable cetaceans, and one of the best loved by the public.

The name and the family

The word “beluga” comes from the Russian belukha (the male) or belugha (the female), derived from the adjective belyi, “white”. The name points directly to the colour of the adult. It should not be confused with the beluga that also names a large sturgeon of the Caspian Sea, two unrelated species bearing identical names.

The beluga belongs to the small family of the Monodontidae, which holds only two species: the beluga and the narwhal (Monodon monoceros). These two Arctic cetaceans are close cousins, sharing several anatomical features linked to their adaptation to the sea ice. Both are odontocetes, toothed whales, evolutionarily related to dolphins and killer whales.

A whiteness that comes with age

The classic image of the beluga is of an entirely white cetacean. But this whiteness is not there at birth. Calves are born dark grey, sometimes almost brownish. Their coloration lightens gradually with age, turning grey, then whitish, and finally entirely white at around 6 to 8 years, which corresponds to sexual maturity.

This feature, a pale adult and a dark juvenile, is rare among marine mammals. It could offer the young a camouflage advantage against predators (killer whales in particular, which now enter the Arctic more readily as the ice melts), while the white adult colour would serve for camouflage in the sea ice and for visual communication within the group.

A modest size and a mobile forehead

The beluga is modest in size for a cetacean: 3 to 5 metres long, weighing from 500 kg to 1.5 tonnes in large males. Its body is stocky, with no dorsal fin (an adaptation to life beneath the sea ice, where a dorsal fin would hinder swimming under the ice).

Its most remarkable anatomical feature is its exceptionally mobile domed forehead: the melon. In most cetaceans the melon is a relatively static structure. In the beluga it is so deformable that the animal can literally be seen bulging it, drawing it back, pointing it through active muscular contractions. It is one of the few cetaceans in which this mobility is visible to the naked eye. The melon focuses echolocation sounds, and deforming it allows the beluga to steer its acoustic beam actively, much as one would aim a torch.

The canary of the sea

The nickname “canary of the sea” dates from the nineteenth century, when sailors heard the beluga’s remarkably varied vocalisations through the hulls of their ships. Its acoustic repertoire combines whistles, clucks, clacks, creaks and many other sounds, a genuine underwater concert. The beluga can produce up to 50 different types of vocalisation, which makes it one of the most “talkative” cetaceans known.

More extraordinary still, cases of vocal mimicry of human speech have been documented in captivity. The best known is NOC, a beluga kept at San Diego in the 1980s, able to reproduce sequences resembling human words so closely that for a time a diver was thought to be speaking. NOC managed to alter the pressure in his nasal passages to imitate the frequency and the envelope of the human voice, an exceptional feat of vocal learning.

A threatened Arctic cetacean

Belugas live mainly in Arctic and subarctic waters: Russia, Canada, Greenland, Alaska, Norway. They form relatively distinct populations, some migratory (the belugas of the Beaufort Sea), others resident (the isolated population of the St Lawrence estuary in Quebec, for example).

The St Lawrence population is emblematic. Estimated at about 900 individuals, it is severely threatened by chemical contamination: the belugas there carry some of the highest PCB levels in the world. Females pass these contaminants into their milk, compromising the reproductive health of the whole lineage.

More broadly, climate warming is rapidly altering Arctic habitats. The melting of the ice is opening new shipping routes (with the noise that comes with them), letting killer whales move further north (a new predator), and disturbing the prey species the beluga depends on. For a cetacean adapted over thousands of years to icy waters, the future is being written in a rapidly changing Arctic, a major challenge for its long-term survival.

---

Further reading