The bodies of bearded seals are cigar-shaped, yet with a small head, decorated with a splendidly long and bushy moustache © BMJ, Shutterstock
Seals are well adapted to aquatic life in polar regions, cushioned and insulated from the cold air as effectively as they are from cold water with a thick coat of blubber and dense pelage. There are two main divisions – or Superfamilies – in the Pinnipeds. First the Otariidae which includes fur seals, sea lions and walruses. In the Arctic, the main representative of these ‘eared’ seals is the walrus (although the northern sea lion has a stronghold in the Bering Sea). The other major grouping is the Phocidae, the ‘true’ seals which have no protruding external ear, cannot run or raise themselves on fore-flippers, cannot swivel their hind flippers and must clumsily haul or hump themselves on land in caterpillar fashion. These are well represented in the Arctic.
Seals have torpedo-shaped bodies superbly designed for fast underwater travel. Their nostrils are closed and sealed by muscular contraction as they enter the water and they exhale before diving to reduce the amount of air in their lungs, deriving the necessary oxygen from their well-supplied blood systems. Their heart rate reduces and slows and their metabolism is reduced. On surfacing it is several minutes before their heart rate returns to its usual surface beat.
Breeding must occur ashore, but they are comfortably able to pup on the fast ice. Males and pregnant females gather annually at the breeding place, where copulation takes place soon after the previous year’s pups are fully grown. Implantation is delayed for three months so that although the gestation period is nine months the annual cycle is maintained.
Polar bears and killer whales are their natural enemies, but seals have also suffered greatly from the depredations of human sealers.