Beluga – Delphinapterus leucas
Habitat: Cold waters near or within sea ice. Briefly enters estuaries and river mouths in summer, probably linked to moulting. Migrates ahead of advancing polar ice front in many arctic regions but in some areas occurs year round.
Description: Skin is soft and white or yellowish, calves grey, often blotched. Head looks unusually small compared to body, slight beak. Melon is bulbous and malleable. Neck is uniquely flexible and visually distinct. 8 – 11 pairs of peg-like teeth in upper jaw, 8 – 9 pairs in lower jaw. May be worn flat to gumline in older adults. Fins are short, rounded, turned up at times. Flukes are deeply notched and develops lobe on each side of trailing edge with age. No dorsal fin; instead there is a spinal ridge.
Size: female 3 – 4m (max. 4.7 m), male 4 – 5 m (max 5.7 m). Larger further north.
Weight: female 400 – 1000 kg, male 1000 – 1700 kg.
Lifespan: Difficult to establish. Few animals reach 30 years, 40 years is exceptional.
Distribution: Arctic, circumpolar regions. Seasonal distribution largely dictated by annual sea-ice cycle. Most reliable sightings around British Isles off North Sea.
Diet & Feeding: Varied. Mostly fish, both benthic and pelagic, depending on seasonal habitat, with squid and invertebrates taken in various parts of range. Feeds near surface and on seabed at depths of up to 550 m.
Breeding: Single calf born in late spring to early summer, at time of entry to warmer coastal waters or before. Gestation period probably 13 – 15 months, lactation lasts for 2 or more years, calving interval probably 3 years. Mating occurs in late winter – early spring. Both sexes probably reach sexual maturity at 5 – 8 years, with males maturing a year or two later than females in the same population.
Conservation Status & Population: Listed by IUCN as vulnerable. Total world population probably around 150,000, with possibly 30 different stocks around the arctic. Most populations have been hunted and native harvests continue in some areas. Maintained in many captive facilities and trained by US and Soviet naviews for submarine warfare roles. Increasing human activities in areas seasonally occupied by belugas have caused habitat loss. Other issues include disturbances from vessels, capture in fishing gear, and pollution.
Uniformly white in adulthood, smaller animals shades of grey. Neck flexible due to unfused vertebrae (unique amongst cetaceans). Lacks dorsal fin.
Vocalisations: Very vocal when socialising, variety of whistles, chirps, and grunts heard clearly above and below water. As many as 50 call types recognised. Communicative and emotive calls broadly divided into whistles and pulsed calls, usually around 0.1 – 12 kHz. Excellent echolocation adapted to ice-covered waters, capable of detecting targets at distance with high levels of ambient noise and backscatter.