SEALS OF SVALBARD
The bearded seal is the largest of the Arctic seals. This seal is characterized by its moustache, rectangular body and relatively small head. Bearded seals are almost always seen resting on sea ice and rarely on shore. In areas free of hunters you can closely approach these seals when they are on the ice.
Ringed seal, harbor seal and harp seal are other common seals on Svalbard. The ringed seal is the only seal that can keep ice-free breathing holes in thick ice, right up to the North Pole. Seals are the favorite food of the polar bear, especially the ringed seal.Young ringed seal peeking out from behind a piece of ice on the east coast of Spitsbergen. Copyright: Roy Mangersnes
The Bearded seal is the largest of the Arctic phocids (true seals) with body mass of well over 400 kg.
They got their English name because of the very long facial whiskers that tend to curl when dry.
Studies of animals from Svalbard have shown that these whiskers are very sensitive, with more than 1300 nerve fibers per vibrissae. This is among the highest density reported for any animal (for comparison a cat has about 200).
Newborn pups weigh more than 10% of their mother’s weight, and are able to swim and dive when just a few hours old.
In Svalbard many of the bearded seals have deep rust-coloured faces. In some animals the fore-flippers are also rust-coloured. Element analyses of the fur show that iron oxide (in other words rust) is responsible for this discolouration. While feeding in seas with soft-bottom sediments the seals faces and flippers make contact with the rich deposits of iron mono-sulphide. When this sediment is disturbed and mixed into the water column by the seals, the iron mono-sulphide is oxidized to form iron oxides that precipitate into the hair shafts of the seals. During the annual moult, the rust-coloured hairs are replaced by new hairs with “normal” colouration.
Instrumentation of bearded seal pups and adults in Svalbard have shown that the deepest dives are recorded by pups during the first months after they leave their mothers. From such individuals we have recorded several dives deeper than 450 m, whereas we have no recorded dives of adults below 400 m. This is likely due to the fact that the animals normally feed on prey that lives on the bottom in relatively shallow water. The adults know this and don’t waste time diving to depths were food is not present. The pups on the other hand have to learn this “the hard way”.
Bearded seal on glacier ice with a red colored head, tinted by sediment deposits on the sea floor. Copyright: Roy Mangersnes
Ringed seal is the most ice-associated of all seals, it has a circumpolar distribution, is the main prey for polar bears, and the reason that many Inuit communities have been able to establish themselves as far north as they have.
The small white-coated pups are normally born in caves that are constructed by their mothers in the snow covering a breathing hole in the fast-ice.
As an adaptation to avoid predation, the small pups are able to swim and dive long before they are weaned by their mothers. In Svalbard these pups still in their white coat, only a few weeks old, have been instrumented and shown to dive deeper than 90 m and stay under water for more than 12 minutes.
Ringed seals are impressive divers for their small size. A 37 kilogram young female from Svalbard that was equipped with a dive logger dove down to 494 meters depth.
They are one of the longest living of all seals, and in Svalbard animals up to 45 years of age are recorded.
Seals, like most mammals, are aged by counting growth layers in their teeth, much in the same way as we age trees.
The adult male ringed seals defend underwater territories (“maritories”) in the fast-ice during the breeding period in the spring.
The adult male ringed seals secrete a strong smelling sulphur compound from glands in their snout during the breeding period. In this period also the meat from these animals is inedible due to various “rut-flavours”.
Ringed seal pups are very important food for polar bears, and when the snow cover is low they are easy prey to catch. Copyright: Roy Mangersnes
Harbour seals are very broadly distributed in Northern Hemisphere; from Japan to California and northwards in to the Pacific Ocean, and from the USA and France in to the Atlantic Ocean.
The world’s northernmost population is found in Svalbard. This genetically isolated population is more closely related to Greenland harbor seals than those from the Norwegian mainland.
They prefer to haul-out on shore and will likely become a “climate-winner” increasing in distribution and numbers as climate change forces the ice to recede northwards.
Haul-out behaviour is generally closely linked to tidal cycles as many of the sites only are exposed during low tide. In Svalbard this pattern disappears during winter when the seals haul-out on sea ice.
Pups are born on shore but can swim during the first high tide after birth.
Many have wondered how seals can find and capture fish at depths where the light is very weak, or during the polar winter when light is completely lacking. Experiments with harbour seals in captivity have shown that the seals detect fish using their very sensitive whiskers. When a fish swims through the water it creates a hydrodynamic trail that the seals can detect for well over a minute after the fish has passed. Thus they can home in on the fish and capture it without using their eyes at all. This also explains why blind seals who are in good condition have been observed all over the world.
Harbour seals like to rest on submerged rocks along the shoreline. Copyright: Roy Mangersnes
Harp seals are the most numerous seal in the Northern Hemisphere (8-10 millions).
They breed in huge herds on drifting pack-ice (many 10’s of thousands).
The harp seals nurse their white-coated pups for only 12 days – then the pup is left to itself.
Harp seals are highly social animals usually travelling in herds. This occurs both in and outside the breeding season.
When the harp seals are disturbed they can often be seen swimming on their back and jumping half way out of the water.
Hooded seal is only found in the North Atlantic Ocean.
They are extreme divers with recorded dives deeper than 1500 meters and lasting more than 1 hour.
Hooded seal breed in trios (an attending male, a female and her pup) in relatively heavy pack-ice.
They have the shortest lactation period of any mammal – only 4 days. The pup is then abandoned by its mother, and has normally not been in the water at all.
Males have 2 “balloons”, a “hood” and the nasal septum, that they blow up to attract females and signal superiority to other males.
he pup will double their body mass in this period due to high intake of extreme fat rich milk (almost 70% fat (“whole milk” in stores from cow is 3,9% fat). The seal pup put on as much as 12 kilograms a day during this period.
Hooded seal male in the pack ice north of Hinlopen. Hooded seals like to lay high up on a ice mount. Copyright: Roy Mangersnes