(Erxleben, 1777) - Hooded seal
Hooded seals are sexually dimorphic. Both sexes are robust, with large, wide, and relatively short heads. The muzzle is very wide and fleshy; it overhangs the mouth and droops slightly in adult females and subadults. In adult males, however, there is an inflatable nasal cavity in the form of a black bladder. When flaccid, it hangs down in front of the mouth; when inflated, it forms a taut, crescent shaped hood that almost doubles the size of the head and substantially elevates the profile. Male hooded seals also can close the right nostril, extruding a membrane from the left nostril as a brownish to bright red balloon-like structure. The flippers are relatively short, and are slightly pointed and angular with a longer first digit. The vibrissae are beaded, relatively short, and inconspicuous; they are dark in pups and light in adults.
Adults are silvery grey, with scattered, irregularly sized, dark blotches. These blotches coalesce on the head and muzzle. The foreflippers are generally dark. Pups are called “bluebacks,” born in a handsome coat of dark blue-grey above and creamy white below. The dark colour continues onto the hindflippers and also extends downward to include the foreflippers. The pale colour rises high on the flanks and neck, and encompasses the lower jaw. Bluebacks retain their coat until the following summer. The face and muzzle are very dark, almost black, to behind the eyes.
The dental formula is I 2/1, C 1/1, PC 5/5.
Can be confused with
Hooded seals share their range with 5 other phocids. Harp, harbour, ringed, bearded, and grey seals can be distinguished by pelage colour, and head shape and size. Hooded seals are most likely to be confused on ice with bearded seals, and additionally in the water, with harp seals. Harp seals are small and uniquely marked. Bearded seals are larger with a small head and “bearded” look.
Adult males reach lengths of 2.6 m and weights of 300 to 400 kg; females average about 2 m in length and weigh 145 to 300 kg. Pups are born at 87 to 115 cm and weigh 20 to 30 kg.
Hooded seals are found in the Atlantic region of the Arctic Ocean, and in high latitudes of the North Atlantic. They breed on pack ice and are associated with it for most of their lives, shifting their distribution with its seasonal fluctuations. There are 4 major whelping areas. Hooded seals wander widely, and have been found as far south as Florida and Portugal. Astoundingly, 1 female recently made her way to San Diego, California, on the opposite side of the continent from the species' normal range.
Biology and Behaviour
Hooded seals pup away from floe edges, on pack ice in March and early April. Females are usually widely separated and aggressively defend their pups. Remarkably, pups are weaned in an average of only 4 days, the shortest time for any mammal. Males are territorial and patrol the ice edge; they often haul out near females, forming trios. Bulls actively fight among themselves, and can inflict bloody wounds; they routinely display by inflating their nasal bladders and extruding their nasal septum to ward off competing males. They also vocalize at the same time by shaking the balloon violently, producing a loud “pinging” noise. Mating usually takes place in the water.
Hooded seals typically fast during breeding and moulting, but actively feed during much of the rest of the year. Their diet is poorly known, but appears to consist primarily of squids and fishes. It includes both coastal and benthic species, suggesting a coastal distribution for at least part of the year.
Like most other Arctic pinnipeds, hooded seals have been hunted by people since prehistoric times. There has also been a long history of commercial sealing for this species, for oil and, particularly for the luxurious coats of the bluebacks. Hooded seals are still hunted in Greenland for meat for humans and dogs, and for pelts. Also, an unknown number are killed every year by incidental entanglement in fishing nets.