White whale, Delphinapterus leucas (Introduction, description, distribution, feeding) – Video

This video was filmed at the Sea World, California, USA (June 2012)

Review: Abdel Rahman El Gamal (Founder of the website and video channel)

Introduction: The beluga whale and white whale are the common names for the Arctic and sub-Arctic cetacean species, Delphinapterus leucas, which belongs to family “monodontidae”.  We preferred to use white whale to avoid confusion with the beluga sturgeon.

Description: The adult white whales are distinguished by their pure white skin while calves are usually gray when born and gradually turn towards white coloration as they grow. Like most toothed whales it has an oily, fatty tissue lump (distinctive protuberance) on the center of the forehead. Male whales are larger than females whereas the average male length is about 4 m compared to about 3.6 m in females. The same trend is true for weight whereas the weight range for males runs between 1100 and 1600 kg while the weight range for females is between 700 and 1200 kg. Unlike most whales, the white whale is capable of swimming backwards.

In order to get adapted to ice condition, belugas have a dorsal ridge and not a dorsal fin. It is believed that the dorsal ridge suits under-ice conditions. Also, as in other cetaceans, the thyroid gland is relatively large compared to terrestrial mammals and this and may help to sustain higher metabolism during the summer estuarine occupations.

Distribution and habitats: Globally, white whales are found mostly in Arctic and sub-arctic waters, particularly along the coasts of Alaska, Canada, Greenland, and Russia.

There are key factors influencing the distribution of white whales especially during the ice-free months. These factors include the accessibility to food, water quality, and predator avoidance.

As expected, factors that may affect the prey populations, will ultimately affect the distribution of the whales. Such factors may include water quality, water pollution, coastal vessels, vessel traffic and others.

When the whales move away for winter, they may either stay close the edge of icepack during the winter months or they may stay under the icepack while they find patches of open water in the ice through which, the whales can surface and breathe.

Feeding habits: The white whale is a slow swimmer that feeds mainly on fish, cephalopods (squid and octopus) and crustaceans (crab and shrimp). Whales forage for food on the seabed which typically takes place at depths of up to 300 m. A typical feeding dive lasts 3–5 minutes. The primary fish prey for Belugas are eulachon and salmon especially during the seasonal salmon runs. Other fish prey includes herring, halibut, whitefish, arctic cod and several other bottom fish species. Feeding on fatty prey allows whales to build enough fat reserves to meet metabolic demands and persist through the winter when their food becomes scarce.

The nutritional status, prey abundance and fat reserves is reflected in the skin thickness of the animals whereas blubber thickness over the winter is reduced to 2-3 cm compared to about 30-cm thickness by the fall after the active feeding of whales on the abundant fish stocks throughout the spring and summer.

It worth mentioning that pregnant and/or nursing whale female would consume more prey in order to meet the increased energetic demands as required by pregnancy or lactation especially calves do not feed on fish until about 12 months of age.

References: Natural history notebook, Wikipedia, Scientific papers

Permanent link to this article: https://fishconsult.org/?p=4992

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