Hooded seal

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Hooded seal
Scientific classification
Kingdom Information
Kingdom Animalia
Phylum Information
Phylum Chordata
Class Information
Class Mammalia
Order Information
Order Carnivora
Family Information
Family Phocidae
Genus Information
Genus Cystophora
Species Information
Species C. cristata
Population statistics
Population 592,100 (2006 est.)

The hooded or bladder-nosed seal (Cystophora cristata)is a true seal native to the Arctic which is known for the air sac upon its head from which it is named.

Contents

Description

Adults have black heads and silver-gray coats with dark blotches of varying sizes and shapes across their bodies. Pups are called "blue-backs" for their coat of blue-gray on their backs and whitish bellies; this coat is shed after 14 months of age when they molt.

Adult males measure around 8 feet (2.5 m) long and weigh about 660 pounds (300 kg). Adult females are noticeably smaller, measuring around 7 feet (2.2 m) in length and weighing about 440 pounds (200 kg).

The hooded seal is unique for the elastic bi-lobed nasal cavity, or "hood", that adult males can inflate and extend from the front of their face to the top of their head. Sexually mature males also have an elastic nasal septum, which, when inflated, resembles a pinkish red balloon, to attract females' attention during mating season and to display hostility towards other males.

The hooded seal is an unsocial species and is more aggressive and territorial than other seals, migrating and remaining alone for most of the year except during the mating season. Females mature in about 3-6 years and males in 5-7 years, when they begin their annual migratory cycle. They gather in the spring at their usual breeding grounds for 2-3 weeks and produce offspring, after which they linger in the area to molt before beginning their annual period of migration for the remainder of the year. Hooded seals live for about 30-35 years.

At birth, hooded seal pups measure about 3 feet (1 m) long and weight around 55 pounds (25 kg). Hooded seal pups are weaned between 3-5 days, the shortest time of any known mammal. Within the lactation period, the pup's body weight nearly doubles, increasing from about 50 pounds to 90 pounds (22 kg to 42 kg) in 4 days (Bowen, 1985). After they are weaned, pups begin to find food alone, mainly feeding on crustaceans, and improve their swimming and diving skills. There are limited data and observations on juvenile hooded seal available, because they appear to spend a great amount of time in the water and in remote areas (Kovacs, 2002).

Hooded seals usually dive for food to depths of about 325-1,950 feet (100-600 m) for 15 minutes, but have been found to dive to over 3,280 feet (1000 m) for up to an hour each time. Adult hooded seals feed on squid, starfish, mussels, and fish such as Greenland halibut, redfish, cod, capelin, and herring.

Habitat and distribution

Hooded seals inhabit the Arctic Ocean and the North Atlantic, living on drifting pack ice and in deep waters. Some drift far away from their northern habitat towards much warmer regions every year, but they survive best in colder climates, as heat and constant sun exposure is harmful to them. The four main breeding and molting grounds are:

  • Gulf of St. Lawrence,
  • off the coast of Newfoundland and Labrador,
  • Davis Strait, and
  • Norwegian Sea, near Jan Mayen Island (Folkow & Blix, 1995).

They are abundant in these areas during the mating season, which begins in late winter and lasts through April, before dispersing for the summer and fall. Hooded seals are migratory and can wander long distances; they have occasionally been found as far south as Florida, California, and the Caribbean.

Threats

Hooded seals were heavily hunted along with harp seals, mainly by Norway, the Soviet Union, Canada, and Greenland. Adult hooded seals were hunted for oil and leather before the 1940s. Then, pups were targeted for their beautiful blue-back pelt, and in the process, many mother seals that were protecting their pups were killed. Protection of the hooded seals began when their population was visibly diminishing. Human-caused mortalities of hooded seals have declined dramatically since the implementation of protective measures in the 1980s.

Still, illegal harvesting continues and hooded seals are taken as by-catch, such as in lumpfish and groundfish gillnets in Canada. In addition, there has been a recent rise in the number of hooded seals found stranded in warm regions. Reasons for the increase in extra-range strandings are currently unknown.

The known natural predators of hooded seals are polar bears and killer whales.

References

  • Kovacs, K. M. (2002). "Hooded seal Cystophora cristata". Pp. 580-582 in W. F. Perrin, B. Wursig, and J. G. M. Thiewissen, eds. Encyclopedia of Marine Mammals; Academic Press.
  • Bowen, W. D., O. T. Oftedal and D. J. Boness (1985). "Birth to weaning in 4 days: Remarkable growth in the hooded seal, Cystophora cristata". Canadian Journal of Zoology, 63(12), 2841-2846.
  • Folkow, L.P., and A.S. Blix (1995). "Distribution and diving behavior of hooded seals". Pp. 193-200 in A.S. Blix, S. Walloe, and Ø. Ulltang (Eds.) Whales, Seals, Fish and Man. Elsevier Science, Amsterdam.
  • Report of the Working Group on ICES/NAFO Working Group on Harp and Hooded Seals (WGHARP), 12-16 June 2006, ICES Headquarters. ICES CM 2006/ACFM:32. 28 pp.


Copyright Details
License: Some of this work is in the Public Domain in the United States because it is a work of the United States Federal Government under the terms of Title 17, Chapter 1, Section 105 of the U.S. Code
Source: File available from the United States Federal Government [1].
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