White whale (Delphinapterus leucas)
White whales are a mid-sized toothed whale. They are found in most arctic and sub-arctic waters, including the Arctic Ocean and its adjacent seas. Males reach lengths of 4.5 metres and 1,500 kg. Females are somewhat smaller reaching 4 metres and 1,200 kg. The number of white whales in Svalbard is not known, but they are the most numerous cetacean species in the area and also the most commonly observed whale. White whales are very social animals that travel in groups virtually all the time.
White whales are a mid-sized toothed whale (Odontocete). Males reach lengths of 4.5 metres and 1,500 kg. Females are somewhat smaller reaching 4 metres and 1,200 kg. White whales lack a dorsal fin but they have a prominent dorsal ridge that is used to break through thin ice. They have small eyes, a bulbous melon on the front of their heads, and a flexible neck (unlike most cetaceans that have fused neck vertebrae). They have small flippers and a small fluke. When white whales are born they are creamy-grey in colour, but turn dark grey rapidly. They are approximately 140 cm long and weigh 50-60 kg. They fade in colour over their juvenile years becoming lighter each year until they are eventually white. Females are white by about age 14, whereas males are about 20 when they are completely white. White whales can appear a rusty yellow prior to their annual moult during the summer. During their moult white whales shed an outer cork layer as well as the top layers of skin; this special ”cork” is unique to white whales and the closely related narwhal; it thought to be an adaptation to protect the skin from ice-abrasion.
White whales are found in most arctic and sub arctic waters, including the Arctic Ocean and its adjacent seas. However, their distribution is somewhat disjointed in that they are virtually nonexistent in the Greenland Sea. A small, southern population of white whales resides in the St Lawrence River in Canada. White whales exhibit highly variable movement patterns in different geographical areas of the Arctic (see below). In Svalbard, white whales exhibit a tightly coastal distribution, never leaving the near-shore waters of the Archipelago.
The global population of white whales is not accurately known, but adding the numbers from all of the various stocks results in a figure of about 200,000 animals. The number of white whales is Svalbard is not known, but they are the most numerous cetacean species in the area and also the most commonly observed whale. White whales are very social animals that travel in groups virtually all the time.
Most populations are extremely vocal – which has given this species the popular name canaries of the sea. However, inSvalbard white whales are remarkably quiet for unknown reasons. There is significant sexual segregation among groups of white whales with females, calves and juveniles travelling together, while adult males form separate groups. Groups are not fixed entities, they seem to divide and reconsolidate through time. Beyond this basic knowledge, the social dynamics of this species are not well documented.
Across their range, white whales display highly variable patterns with regard to seasonal movements. In some areas they exhibit marked migratory patterns, while in other areas they remain resident year round. In some regions they spend a lot of time in coastal areas, occasionally even in estuarine areas, during summer – while in other areas they occur far offshore. In some regions white whales tend to follow the seasonal movement patterns of the sea ice, remaining near the expanding or retracting ice edges. Although the winter whereabouts of white whales are poorly known, it is assumed that they either over winter in polynyas and ice leads or they migrate in the direction of the advancing polar ice. InSvalbard, white whales remain very close to the coasts. During the early winter they have been documented travelling deep into drifting ice where the ice cover was more than 90%.
Different foraging strategies might play a role in the different movement patterns observed across the species range. White whales usually feed in waters above the continental shelf, often at discrete coastal locations at least during the summer months. In Svalbard white whales spend a lot of their time along tidal glacier fronts, during the ice-free season, presumably because up-welling in these areas result in concentrations of prey being available. Similar to other toothed whales, white whales use echolocation during foraging and probably also when travelling in murky water to avoid striking objects. White whales are quite slow swimmers but they can dive to depths greater than 1,000 metres, though in the Barents Sea Region water depths limit their diving to a few hundred metres. White whales consume a wide variety of prey items ranging from benthic invertebrates and squid to pelagic fishes. In summer they often feed on seasonally abundant anadromous (salmonids) and coastal fishes in some parts of their range. In western Greenland white whales consume pelagic polar cod and arctic cod. InSvalbard their diet appears to be dominated by polar cod with capelin and shrimps also being consumed.
Polar bears and killer whales are both predators of white whales. If white whales become trapped in cracks or polynyas polar bears can harvest the entire pod as they weaken after repeated attacks each time they surface to breathe. Killer whales are thought to be a major force in keeping white whales tightly associated with ice, where these predators cannot follow them.
Life history and reproduction
Births can be spread from May to late August. Calves are cared for by their mothers for over two years and remain in the maternal social group for years following weaning and continue to associate with their mothers.
White whale mothers are very solicitous of their young, and young calves are virtually always in physical contact with their mothers when they are small. Mother–calf pairs are very vocal, which presumably helps them to maintain contact.
Mating occurs in late spring (April–May). The mating system of this species is not known.
White whale females reach sexual maturity at about five years of age, whereas males are somewhat older (eight years). The species lives to an age of approximately 40 years.
Management status and monitoring
White whales are harvested for subsistence purposes throughout most of their range in the Arctic. In some areas the numbers taken are significant because their coastal distribution in summer makes them readily available to shore-based fisheries. It is one of the most important species in traditional hunts in coastal Alaska, the eastern Canadian Arctic and Greenland.
The species have been subjected to commercial harvests by various nations at various times, and until very recently were commercially harvested by Russia in the White Sea. In Svalbard Russian whalers began harvesting this species early in the 17th century, mainly operating in the fjords on the West Coast of Spitsbergen. Norway and other nations commenced hunting for white whales in this region in the late 1800s when the larger whales became scarce. White whale harvesting continued through until the early 1960s.
Recovery seems to be taking place in Svalbard in the last decades; pods of whales numbering into the thousands are sighted irregularly around the Svalbard archipelago and pods ranging from a few individuals to a few hundred individuals are seen with regularity.
White whales are protected in Svalbard.
MOSJ indicators (Environmental Monitoring of Svalbard and Jan Mayen):
Awaiting results from MOSJ…