Hooded seals are large sexually dimorphic phocids. The muzzle is wide and droops slightly, overhanging the mouth in adult females and subadults. In adult males, 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 taught, bi-lobed crescent-shaped hood that almost doubles the size of the head and substantially elevates the profile. Another secondary sexual characteristic of male hooded seals is that after partially inflating the hood they can close a nostril and extrude the elastic bright red nasal septum from the other nostril and inflate it like a balloon. The flippers are relatively short, 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. Hooded seals have two mammae, typical of most northern phocids.
Adults are silvery white, with numerous, small to large, irregularly shaped dark blotches and clusters of blotches. The head to behind the eyes and jaws, and the tops of the fore flippers are blackish. Pups are called “blue-backs,” born in a handsome coat of dark blue-gray above and creamy white below. The dark color continues onto the hind flippers and also extends downward to include the fore flippers. The face and muzzle are very dark, almost black, to behind the eyes. The pale color rises high on the flanks and neck, and encompasses the lower jaw. Blue-backs retain their coat until the following summer, when they molt at 14 months and start to develop adult markings as juveniles.
Adult males reach lengths of 2.6 m and weights of 192-352 kg; females average about 2 m in length and weigh 145-300 kg. Pups are born at 87-115 cm and weigh 20-30 kg.
The dental formula is I 2/1, C 1/1, PC 5/5.
Can be Confused With
Hooded seals share their range with five other phocids. Harp, harbor, ringed, bearded, and gray seals can be distinguished by pelage color, 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, densely-packed downward-pointing vibrissae, and four mammae.
Hooded seals are found in 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 seasonal fluctuations. There are four major whelping or pupping areas: the Gulf of St. Lawrence, north of Newfoundland and east of Labrador, in the Davis Strait, and near Jan Mayen. Hooded seals can wander widely, and animals have beached as far south as Portugal in Europe, and from New England to Florida in North America. An exceptional journey was made by an animal found in San Diego, California, that presumably crossed the Canadian Arctic and Beaufort Sea, and then traveled down the Bering Sea to a location well south in the eastern North Pacific.
Ecology and Behavior
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, often hauling-out near females and forming trios. Bulls actively fight among themselves, and can inflict bloody wounds; they routinely display by inflating their black nasal bladders and extruding their nasal septum, shaking this bright red balloon violently in efforts to ward off competing males. They also vocalize at the same time by and producing a loud “pinging” noise. Mating usually takes place in the water.
The pack ice edge is home to hooded seals throughout the year and they migrate with it as it retreats north in summer and advances south in the fall. Aggregations form in the Denmark Strait east of Greenland and near Jan Mayen during the late spring molt, which begins after the pupping season. Following the molt, they disperse widely for the summer and winter, primarily living along the ice edge.
Hooded seals are deep divers and are capable of long dives. The maximum-recorded depth reached is over 1,000 m and the longest dive has been nearly one hour. Typical dives while foraging are to depths of 100-600 m and last around 15 minutes. Polar bears and killer whales are known hooded seal predators.
Feeding and Prey
Hooded seals typically fast during breeding and molting, 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 such as Greenland halibut, Atlantic and Arctic cod, several redfish species, herring, and capelin. Newly weaned pups feed on pelagic crustaceans prior to taking on the adult diet.
Threats and Status
The current worldwide population of hooded seals is estimated at 550,000. They have been subjected to episodes of intense commercial hunting from the late 1800s to the late 1900s. Harvests were often conducted in association with harp seal harvests and commercial fisheries for Greenland sharks. Norway, the Soviet Union, Canada, and Greenland have been principally involved in the commercial harvests, which were primarily focused on newborns, because of their highly prized blue-back pelt. A permanent import ban on hooded seal pelts by the European Economic Community ended most of the commercial harvesting of this species, although Canada took approximately 26,000 as recently as 1996. Harvest levels have also been lower in many cases than the reported number of takes, due to killing of females that aggressively defend their pups, and loss of animals that are injured, enter the water, and sink after dying.
There is a large annual by-catch of hooded seals in coastal net fisheries in Norway. Hooded seals are important in subsistence harvests on both coasts of central and southern Greenland, where they are used for food for humans and dogs.