A Review of the Developmental, Behavioural and Physiological Adaptations of the Ringed Seal, <i>Phoca hispida</i>, to Life in the Arctic Winter

Abstract

Ringed seals, Phoca hispida, the smallest of the marine arctic pinnipeds, are one of only two seal species in the world adapted to life in the land-fast sea ice. The habitat is characterized by a stable ice platform forming in early winter and lies at latitudes subject to extreme low temperatures. The small body size of adults and semi-altricial pups are an unusual adaptation to cold, allowing ringed seals to use shelters that they construct in the snow overlying their breathing holes. These small subnivean structures act to hide adults and pups from predators, especially polar bears, U r n marifimus, and arctic foxes, Alopex lagopus. It appears that dry lanugal pups could withstand the arctic cold without shelter, but pups that have been wetted become hypothermic and require shelter to regain thermoneutrality. Since female seals actively swim away with their pups from attacks on their birth lairs by foxes and bears, both the physical and the thermal protection of alternate subnivean lairs are important for the survival of the neonate. Weddell seals, Leptonychofes weddelli, resident in the land-fast ice of the Antarctic, are the ecological counterpart of the ringed seal. Their large body size is typical of the usual cold adaptive strategy of other polar phocid seals.

Variation in Ringed Seal Density and Abundance in Western Hudson Bay Estimated from Aerial Surveys, 1995 to 2013

“…In the case of unusually cold winters, ice breakup occurs later than normal; thus, predation pressure may be increased because predators can remain on the ice, hunting seals, longer into the spring (Stirling and Derocher, 1993;Stirling et al, 1999). However, early ice breakup can also have negative effects on ringed seals: it may interrupt the lactation period and force pups into the water at an earlier age, resulting in increased energy expenditure, slow growth, and decreased overall fitness Smith et al, 1991;Smith and Harwood, 2001). In addition, warmer spring temperatures and early season rains can melt and degrade birth lairs, increasing exposure of pups to predators (Derocher et al, 2004;Stirling and Smith, 2004).…”

Ringed, Bearded, and Ribbon Seal Vocalizations North of Barrow, Alaska: Seasonal Presence and Relationship with Sea Ice

“…Throughout their circumpolar range, they are closely associated with sea ice for most of the year. Their preferred winter habitat is stable ice with ridging or hummocks that facilitate accumulation of snow cover to allow construction of subnivean lairs-conditions that commonly occur in landfast ice Stirling 1975, 1978;Hammill and Smith, 1989;Smith et al, 1991). However, several studies have also found ringed seals overwintering and breeding in drifting pack ice (Fedoseev 1975(Fedoseev , 1997Finley et al, 1983;Wiig et al, 1999).…”

Observations and Predictions of Arctic Climatic Change: Potential Effects on Marine Mammals

“…Ice-associated seals may be particularly vulnerable to changes in the extent or concentration of arctic ice because they depend on pack-ice habitat for pupping, foraging, moulting, and resting (DeMaster and Davis, 1995). Ringed seals (Phoca hispida) and polar bears (Ursus maritimus), which prey on them, are the only marine mammals that regularly occupy extensive landfast coastal sea ice (Smith et al, 1991). Ringed seals require snow cover in which to construct subnivean birth lairs on the fast ice.…”

“…Ringed seals rely on both the duration of the ice cover and the total precipitation to create sufficient snow depth for the building of subnivean lairs (Smith et al, 1991). In this case, while increased snowfall could be beneficial for the construction of lairs, especially on smoother ice with few pressure ridges or ice hummocks, a reduction in the amount and extent of fast-ice habitat could be detrimental.…”