Hooded seal (Cystophora cristata)
|Also known as:||Bladder-nosed seal|
|French:||PHOQUE À CAPUCHON|
|Spanish:||FOCA DE CASCO|
|Size||Female weight: 145 - 300 kg (2)|
Female length: 200 - 220 cm (2)
Male weight: 200 - 400 kg (2)
Male length: 250 - 270 cm (2)
Classified as Vulnerable (VU) on IUCN Red List (1).
The hooded seal owes its name to the striking nasal appendage that adorns the head of sexually mature males. The wide, fleshy muzzle of adult males usually droops down over the mouth, but when inflated it forms a conspicuous bulbous "hood" on top of the head; a display feature that is often enhanced by the extrusion of an internal membrane through one nostril to form a large, pink, membranous balloon. The face is typically solid black in colour, but the rest of the body's coat is silver or bluish grey, with scattered black spots and blotches (2) (3) (4). The flippers are heavily clawed, and being a true seal, the broad, hindflippers are extremely efficient in the water, but useless on land, while the smaller, foreflippers have a primary function in steerage rather than propulsion (2) (5). Owing to their silvery bellies and blue-black backs, hooded seal pups are commonly known as 'blue-backs' (3).
A migratory species with a range that encompasses a large portion of the North Atlantic, the annual movement of the hooded seal generally follows the movement of the pack-ice. There are four main pupping areas including: the Gulf of St Lawrence; an area north of Newfoundland known as the Front; the Davis Strait; and in the West Ice, east of Greenland. Outside the breeding season, it is not uncommon for the hooded seal to be recorded outside its normal range, with juveniles sometimes turning up as far south as Portugal, Florida, and even California in the Pacific (1) (2) (3).
The hooded seal normally maintains a close association with the pack-ice, but will also spend significant periods of time in the open ocean (1) (3).
Aside from the brief attachment formed by a mother with young, or the even briefer union between a mating pair, the hooded seal is relatively antisocial. Indeed, it is only during the moulting and breeding seasons that this solitary species aggregates in loose groups. Lasting only two to three weeks, the breeding season takes place at the end of March, with the females hauling out on ice floes to give birth (2) (3). The pups are born in an exceptionally advanced developmental state, and are weaned after just four days, the shortest lactation period known for any mammal (3) (4) (5). During this time, the mother and pup are usually attended to by an amorous male vying to take advantage of the female's imminent receptivity. In order to assume the position of 'attendant', the males typically compete amongst each other, with the posturing of nasal appendages often being the prelude to more bloody transactions (3). At the end of the brief lactation period, the male and female return to the water and immediately mate, following which the male may go in search of another available female, while the female returns to the open sea to forage. Owing to a four month period of delayed implantation, it will be another year before the female gives birth again. Meanwhile, the abandoned pup remains alone on the ice for several days, or possibly weeks, where it survives entirely on its stored fat reserves (2) (3). Eventually, it will make its first forays into the water, where it must teach itself to swim, dive and forage. As an adult, it will forage for deepwater fish and squid, diving down to depths of over 1,000 metres for over an hour at a time, but while the pup's aquatic skills are developing, krill and other invertebrates must form the bulk of its diet (3) (5). Little is known about the movements of juveniles during the first few years, but upon reaching sexual maturity (three years for females and four, or more, for males), the young adults join the annual migration with the pack ice (3) (4).
Native people of Greenland and Canada have hunted the hooded seal for hundreds of years, but the level of exploitation was amplified significantly during the 19th and 20th centuries, when this species was subjected to intense commercial hunting (1) (2) (3). Up until the 1930s, oil and leather were the main products derived from the hooded seal, but an increase in market demand in the wake of World War II, saw the attractive pelt of the young blue-backs became the primary target. As the commercial hunting of the hooded seal became increasingly unsustainable, numerous legislative measures to protect this species were introduced during the second half of the 20th century (1). Since the implementation of various quotas, agreements and treaties, the hooded seal population in the northwest Atlantic has stabilised, but for unknown reasons the northeast Atlantic population still appears to be declining at an alarming rate (1) (6).
To protect the hooded seal from over-exploitation, a raft of conservation measures, international management plans, quotas, agreements and treaties has been introduced over the last half century. Perhaps most pivotal in reducing the harvest of blue-backs was the European Economic Community’s decision in 1985 to ban the importation of all seal pup products (1) (3) (6). Although subsistence harvesting of the hooded seal continues in Canada and Greenland, all commercial hunting of the young blue-backs is now banned in Canada. Furthermore, the continuous population decline in the northeast Atlantic has led to a moratorium on hooded seal harvests in the region in recent years (1).
To find out more about conservation in the Polar Regions, see:
The Polar Conservation Organisation (PCO):
- Delayed implantation: The process of a fertilised egg remaining unattached in the uterus for a period of time, therefore delaying the start of development.
- Invertebrates: Animals with no backbone, such as insects, crustaceans, worms, molluscs, spiders, cnidarians (jellyfish, corals, sea anemones), echinoderms, and others.
IUCN Red List (November, 2008)
- Nowak, R.M. (1999) Walker's Mammals of the World. Johns Hopkins University Press, Baltimore, Maryland.
- Kovacs, K.M. (2002) Hooded Seal – Cystophora cristata. In: Perrin, W.F., Würsig, B. and Thewissen, J.G.M. (Eds) Encyclopedia of Marine Mammals. Academic Press, London.
- Burnie, D. (2001) Animal. Dorling Kindersley, London.
- Macdonald, D. (2001) The New Encyclopedia of Mammals. Oxford University Press, Oxford.
NOAA Fisheries Office of Protected Resources (December, 2009)