Hooded Seal (Cystophora cristata)
Did You Know? · Pups are weaned in only 3-5 days, the shortest period of any known mammals |
|
Status
MMPA - Hooded seals, like all marine mammals, are protected under the MMPA.
Taxonomy
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Cetacea
Family: Phocoenidae
Genus: Cystophora
Species: cristata
Species Description
Adult hooded seals 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.
The known predators of hooded seals are polar bears and killer whales.
Habitat
Hooded seals live 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.
Distribution
Hooded seals inhabit the Arctic Ocean and the North Atlantic.
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.
Population Trends
In 2005, surveys were conducted to assess population sizes in the main hooded seal habitats. The estimated number of hooded seal pups was 15,200 in Greenland and 116,900 in the Northwest Atlantic (ICES, 2006). Using this data, the total population of hooded seals was estimated to be 592,100. Between 2001 and 2005, mortality and serious injuries of hooded seals due to human actions were estimated to be about 5,200. Data on pup production over many years indicate that population size has been increasing since the 1980s, but not enough information is available to make reliable assertions of population growth.
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.
Mortality and serious injury levels are determined to be negligible relative to overall population size.
Conservation Efforts
Beginning in the 1960s, international cooperation between the main harvesting countries allowed the hooded seal population to recover after years of exploitation. The Northwest Atlantic Fisheries Organization (NAFO) 
, created in the 1970s, managed seal harvesting in international waters, began the licensing of sealers, and set quotas for allowable take. They also prohibited harvesting in defined regions and of blue-backs in all regions. In the early 1980s, the European Economic Community banned commercial harvesting of the hooded seal and importing of any seal products. The first Seal Management Plan was implemented in 1992.
Regulatory Overview
Like all other marine mammals, the hooded seal is protected under the Marine Mammals Protection Act of 1972.
Key Documents
(All documents are in PDF format.)
| Title | Federal Register | Date |
|---|---|---|
| Stock Assessment Reports | n/a | various |
- NMFS National Marine Mammal Laboratory Arctic Ice Seal Information
- NOAA Magazine 2006: Wandering Hooded Seals Puzzle and Challenge NOAA's Stranding Network
- Ocean Biogeographic Information System (OBIS-SEAMAP) Hooded/Bladdernose Seal Species Profile
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.
- ICES. 2006. 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.
