Adult beluga whales grow to lengths of 3–5 m, and can weigh up to 1,500 kg. Males grow slightly larger than females. Newborns are brown or slate-grey in colour and average 1.6 m in length and 78 kg in weight. They become bluish-grey as they mature, then progressively lighten in colour, fading to white after 6 years of age. Most females mature sexually while still light grey, while males become white before maturing. Older males have a marked upward curve at the tip of their flippers.
Beluga mate in the early spring, and calving occurs a little over a year later. Calving for beluga in the Canadian High Arctic population occurs mainly during early July to early August, although calves have been reported there as early as May 31, and as early as late March off west Greenland (Koski et al. 2002). Recent research has shown that belugas may have lifespans of 80 years or more (Stewart et al. 2006).
Photo: M.P. Heide-Jørgensen, Greenland Institute of Natural Resources.
Young beluga begin feeding on fish and invertebrates after their first year, but may continue to take milk from their mothers during their second year of life (Heide-Jørgensen and Teilmann 1994). As the animals grow, they are able to take larger food items, and gradually switch from benthic to more pelagic foraging.
Polar cod (Boreogadus saida) and Arctic cod (Actogadus glacialis) were found to contribute more than any other item to the diet of beluga in the Upernavik area in Greenland (Heide-Jørgensen and Teilmann 1994). Polar cod was also found to be the principle food item for Canadian High Arctic and Svalbard beluga (Koski et al. 2002, Dahl et al. 2000). Squid beaks were commonly found in beluga stomachs from western Greenland. Other prey items found were redfish (Sebastes marinus), halibut (Reinhardtius hippoglossoides) and northern shrimp (Pandalus borealis) (Heide-Jørgensen and Teilmann 1994). Polar cod was also found to be the main prey item for beluga in Russian waters, with various whitefishes (Coregonidae) contributing to the diet in summer (Boltunov and Belikov 2002).
Capelin (Mallotus villosus) are an important food for belugas in the St. Lawrence River and also in Hudson Bay (Kingsley 2002). Other important food items were sand-lance (Ammodytes spp.), Atlantic cod (Gadus morhua), tomcod (Microgadus tomcod), decapod and amphipod crustaceans and polychaete worms.
Did You Know?
A very special neck
Unlike other cetaceans, belugas can move their head up, down, and side-to-side because their cervical vertebrae are not fused. This adaptation is believed to help them manoeuver and catch prey in silt-laden or ice-covered areas.
Recent reductions in Arctic sea ice have made the area more accessible to the killer whale, which is a major predator of belugas. An increased frequency of killer whale sightings has been noted in many areas of the eastern Canadian Arctic (Higdon and Ferguson 2009). This may result in an increase in predation pressure and a concomitant decrease in survival in some beluga populations. You can read more about killer whale predation on belugas here.
Killer whale, Photo: Wikimedia