Ringed seal

Distribution

Ringed seals occur throughout theArctic, north to the pole. They are the only northern seal that can maintain breathing holes in thick sea ice and this special ability allows them to have an extensive distribution in theArctic and sub-Arctic.

In Svalbard, ringed seals breed on the land-fast ice in all of the fjords. They also breed in nearby offshore waters within the free-floating pack ice of the Barents Sea.

During summer ringed seals concentrate in front of tidal glacier (glaciers that end in the sea) fronts in the fjords or move to the edges of the northern ice pack though they can be encountered almost anywhere in Svalbard’s waters on a year-round basis.

General ecology

Ringed seals are the most abundant arctic seal and although no accurate estimate is available, the species is thought to number at least a few million animals globally. The Svalbard-Barents Sea population is thought to number in the hundreds of thousands, but is likely currently in decline.

Ringed seals are in many respects the ‘classical’ arctic ice-seal. This species uses sea ice exclusively as its breeding, moulting and resting (haul-out) habitat — rarely if ever coming onto land. They create or maintain their holes in the ice using the well-developed claws on their fore-flippers. Although ringed seals are quite small phocids they survive the thermal challenges posed by the arctic winter by having a very thick blubber layer, and by building lairs (small caves) in the snow on top of sea ice during the winter. Each seal builds several lairs so that they can escape if a predator attacks one of their structures. Ringed seal lairs in Svalbard’s fjords are often built in snow that accumulates around glacial-ice pieces that freeze into the annually formed fjord ice.

They generally remain in fjords and land-fast ice areas until they have completed their annual moult in June or July. Following the moult some ringed seals move northward up to the ice edge, while others, primarily adult individuals, remain deep in the fjords in association with the front of tidal glaciers. Outside the breeding and moulting periods ringed seals are solitary.

Despite their small size they are capable of diving below 500 m for periods up to 45 minutes. Ice-associated crustaceans and fish, mainly polar cod, constitute much of the diet of ringed seals, although they also eat a wide variety of pelagic and benthic fishes and other invertebrates.

Ringed seals are the favourite food of polar bears. In addition, Arctic foxes prey on pups. In years with poor snow cover birds such as glaucous gulls can also be the source of significant pup mortality. In addition some seal-eating walruses take ringed seals, as do Greenland sharks.

Life history and reproduction

Ringed seals give birth in the early spring to their single pup inside a snow lair. During years with poor snow cover, pups can be born on the surface of the ice, but mortality of these pups is extremely high. Peak birthing occurs in Svalbard in early April.

Ringed seal pups are nursed and cared for by their mothers for approximately six weeks, which is a relatively long period of maternal care among the ice-living seals. During the time they are fed milk the pups increase their body mass approximately four or five times over, to a mass of about 20 kg.

Ringed seal pups are extremely active swimmers and divers that spend about 50% of their time in the water during the nursing period. Pups that are only a few weeks old are capable of remaining underwater for more than 10 minutes and dive to the bottom of the fjords where studies of their aquatic abilities have been performed (90 m). They start feeding on small crustaceans and other invertebrates that are available under the ice while they are still drinking milk.

Toward the end of lactation mating takes place. The embryo then remains dormant for about four months before implanting in the wall of the uterus (‘delayed’ implantation, similar to polar bears) and starting to actively grow. Hence, ringed seals, similar to other phocids, are technically speaking pregnant most of the year, but they have an active gestation period of about eight months.

Populations appear to be structured such that immature animals and young adults are restricted to sub-optimal habitats during the spring birthing and mating season, when breeding adults hold territories in the most stable ice.

Ringed seal females reach sexual maturity at an age of three to five years and males are somewhat older (five to seven years).

Ringed seals are a long-lived species that can be as old as 45 years of age.

Management status and monitoring

Humans have hunted ringed seals in the Arctic since the arrival of people to the region millennia ago. They are a fundamental subsistence food item for most coastally dwelling northern peoples. Their hides have been an important item for making clothing and other household items and have at various times been an important source of cash income for people in the Far North. The species has never been the subject of large-scale commercial hunting because of their dispersed distribution and inaccessibility to hunters.

In Svalbard, licensed hunters can shoot ringed seals from 20 May – 20 March. They are protected during their breeding season. Additionally, ringed seals, like all other species, are totally protected in the national parks and nature reserves in Svalbard throughout the year, The hunt takes from some tens to a few hundred individually annually in Svalbard, depending in part on how many trappers are occupying stations in the Archipelago.

Since 2006 the ice conditions in the fjords on the west coast of Spitsbergen have not been good enough to allow much pup production; some years there has been no breeding ice at all. Sea temperatures have been steadily increasing over the past decade and if sea ice does form, it forms too late to accumulate the snow required for ringed seals to build their birthing lairs. So pups are born onto the bare ice, without the protection of the lair. Few survive predation or inclement weather.

Although ringed seals are long-lived and it is natural to experience significant inter-annual variability in ice and snow conditions, the unidirectional trend in declining sea ice is a clear threat to the ringed seal population in Svalbard, and the broader sea ice community as well.