Bladder-nosed seal, Hooded seal
The hooded seal (Cystophora cristata ) is a large phocid found only in the central and western North Atlantic, ranging from Svalbard in the east to the Gulf of St. Lawrence in the west. The seals are typically silver-grey or white in color, with black spots that vary in size covering most of the body. Hooded seal pups are known as "blue-backs" because their coats are blue-grey on the back with whitish bellies, though this coat is shed after 14 months of age when the pups molt.
The Hooded seal is a large member of the Phocid family, silver-gray with irregular black spots over most of its body and a face which is often completely black. Its most distinctive feature is the male’s prominent nasal ornament, which is a loose, wrinkled sac hanging in the front of the nose. During the time of mating, males will inflate this sac as a form of display to females, as well as to other males. It then becomes a tight, bi-lobed "hood" and covers the face and top of the head. The hood gives the species its common name.
Hooded seals migrate within a range that includes a large area of the North Atlantic, and their migration usually follows the movement of pack-ice. The four main areas for pupping include the east of Greenland in the West Ice, the Gulf of St Lawrence; the Front in the north of Newfoundland and the Davis Strait. Outside of the breeding season, the Hooded seal is sometimes found outside its normal range; juveniles can be seen near Portugal, Florida, and California. This species is normally not too far from pack-ice, but also spends much time in the open sea.
The Hooded seal is diurnal and mostly solitary, except when breeding and molting, at which time it fasts. It does not compete for social hierarchy or territory. The seals gather each July near Denmark Strait before molting. Then they congregate at different sites prior to breeding. These animals can make vocalizations like roars that are easily heard on land. Their most important means of communication is made by their hood and nasal septum. Hooded seals can produce pulses that range from 500 to 6 Hz, which are often heard both in the water and on land. They move their inflated hood and septum up and down, creating “pings” and “whooshes”. Aside from these sounds being a mating display, they can also serve as threats.
Hooded seals are carnivores (piscivores and molluscivores), they eat a range of marine prey, particularly fish, including redfish, herring, flounder and polar cod. They also eat octopus and shrimp.
This species is polygynous. Typically males do not defend personal territories but they will defend an area where a receptive female is. The successful male will then go into the water to mate with the female. On his return to land, he will seek out another female. April to June is the typical period for mating, and gestation lasts 240 to 250 days. A single young is born. At birth young are precocial, able to move around and swim with ease. Being independent at weaning, which is after 5 to 12 days, they are left to look after themselves. Females reach maturity from 2 to 9 years old and most give birth for the first time when they are about 5 years old. Males reach maturity at about 4 to 6 years of age, often not mating until much later.
Historically these seals were heavily hunted, mostly by Norway, Canada, the Soviet Union, and Greenland. Before the 1940s, adults were hunted for leather and oil. Pups were killed for their beautiful pelts of a blue-black color. Many mother seals were killed while protecting their pups. Protection of these animals began when their numbers were visibly diminishing. Today the main threats include illegal harvesting and bycatch, for example, in groundfish and lumpfish gillnets in Canada, competition with commercial fisheries for food, and pollution such as oil spills. Furthermore, as a pack ice-species, global warming may significantly affect the ability to reproduce of this species.
The population of Hooded seals is thought to be relatively large. According to the IUCN Red List, the total population size of the Hooded seal is approximately 675,000 individuals, including 340,000 mature individuals. Currently this species is classified as Vulnerable (VU) on the IUCN Red List.
Hooded seals are predators of many fishes, such as polar cod, squid, and various crustaceans. They may also affect predator populations (sharks, orcas, and polar bears), as items of prey.