Survival rates are not well known, but ringed seals are relatively long-lived and can live in excess of 40 years (McLaren 1958, Lydersen 1998). Their average life span is about 15‐28 years (Kelly et al. 2010b).
Female ringed seals begin to reach sexual maturity at age 3 to 5, but the timing is variable and some may not mature until they are 7 to 8 years old, with geographic and temporal variability depending on animal condition and population structure (e.g., Reeves 1998, Sipilä and Hyvärinen 1998, Krafft et al. 2006b, Kovacs et al. 2008, Kelly et al. 2010b, Kovacs 2014). The mean age at sexual maturity of females has decreased significantly in several areas compared to earlier periods (Krafft et al. 2006b, Kovacs 2014, see also under 'Current abundance and Trends'). Thereafter ringed seal females usually produce a single pup each year, although this may decline if conditions are not favourable (eg. Kingsley and Byers 1998, Kovacs et al. 2008, Kelly et al. 2010). Reproductive success depends on many factors including prey availability, the relative stability of ice, and sufficient snow accumulation prior to the commencement of breeding so that the birth lair can be constructed (Kovacs et al. 2008).
Males mature about 2 years later than females at 5-7 years (e.g. Krafft et al. 2006b, Kelly et al. 2010b) and likely do not participate in breeding before they are between 8 and 10 years old (Kovacs et al. 2008).
Ringed seals can begin to moult as early as late April, with the number of moulting seals increasing in May and peaking in June. The seals spend a lot of time (up to 60%) hauled out on ice basking in the sun both just before and during moulting, a behavior attributed to the need to maintain an elevated skin temperature (Kelly et al. 2010ab). Feeding activity is at a minimum during the spring moult and ringed seals lose a lot of weight and are therefore thin in the summer (Ryg et al. 1990, Rosing-Asvid 2010). Consequently they sink more easily when hunted in the early summer. In August-September, they begin to put on weight again and by December they have returned at their maximum weight.
Approximate annual timing of reproduction and moulting for Arctic ringed seals (from Kelly et al. 2010b). Yellow bars indicate the “normal” range over which each event is reported to occur and orange bars indicate the “peak” timing of each event.
Ringed seals occur in areas of landfast and drifting pack ice over virtually any water depth. While they may prefer areas of landfast ice for breeding, they may also breed successfully in areas of stable pack ice, such as Baffin Bay and the Greenland Sea. Unlike other northern seals such as harp and hooded seals, the ringed seal is completely adapted to ice-covered waters and does not migrate to open water areas in the winter (Reeves 1998).
Instead ringed seals are able to maintain several breathing holes in ice that may be over 2 m in thickness, using their strong sharp foreclaws and teeth to scratch through the ice. This allows them to thrive in areas where even other ice-associated seals cannot reside. During the summer ringed seals forage in areas of pack ice or open water, and may haul out on land where no ice is available.
Ringed seal at a breathing hole. K.M. Kovacs and C. Lydersen / Norwegian Polar Institute
In the summer and fall, when land-fast ice is not available, ringed seals show considerable diversity in their distribution patterns (Kovacs 2014). Some animals remain in the general vicinity of their breeding sites while others disperse along coastlines, concentrating their time near glacier fronts, some spend time in open water far from the coast, and yet others move north to the southern edge of the permanent ice (e.g. Teilmann et al. 1999, Gjertz et al. 2000, Born et al. 2002, Freitas et al. 2008a). Ringed seals are more mobile and have larger 'home ranges' during the open-water season than at other times of the year (e.g., Born et al. 2004).
During the fast-ice seasons, each ringed seal uses several haul-out lairs and additional breathing holes within its home range and travels between them quite regularly. A seal’s lairs are usually only a few hundred meters apart, male’s lairs being spread over greater distances on average than those of females. During the reproductive season females spend more time on average out of the water than males and both sexes shift from hauling out during the night in early spring to hauling out during day-time hours in late spring, with more time spent on the surface during the latter period (Kelly and Quakenbush 1990, Carlens et al. 2006).
Model of a ringed seal pupping lair on the sea ice; Natural History Museum, Copenhagen, Denmark. Photo: A. Rosing-Asvid
It is still unclear whether ringed seals show fidelity to natal sites, or are faithful to breeding sites as adults. This may depend on the quality of the sites (predictable ice stability, sufficient snow to construct lairs, good food availability), and there could be regional and subspecies differences in site fidelity. Ringed seals show a high degree of spatial fidelity (territoriality) in the Baltic (Härkönen et al. 2008). Prime habitat for ringed seals may be used over long periods of time, but there are also reports that strongly suggest that there is considerable mobility among ringed seals in some areas (Kovacs 2014).
Ringed seals can travel significant distances, well over 1000 km (e.g., Kapel et al. 1998, Ridoux et al. 1998). However, satellite tracking studies show that individuals tagged at any one location display variable dispersal patterns, some individuals remaining local throughout the open-water season, while others move offshore or northward to the permanent pack-ice (e.g., Teilmann et al. 1999, Gjertz et al. 2000, Born et al. 2004).
The seasonality of ice cover strongly influences ringed seal movements, as well as foraging, reproductive behavior, and vulnerability to predation (Kelly et al. 2010b).
The diet of ringed seals has been well documented across the species' range, especially in the marine environment (most recently Belikov and Boltunov 1998, Lyersen 1998, Siegstad et al. 1998; Wathne et al. 2000, Holst et al. 2001, Andersen et al. 2004, Carlsen et al. 2006, Stenman and Pöyhönen 2005, Dehn et al. 2007, Agafonova et al. 2007, Labansen et al. 2007, 2011, Vincent-Chambellant 2010, and Kelly et al. 2010b and Kovacs 2014 for review).
Ringed seals are opportunistic feeders and prey on a wide variety of fish and invertebrates, but strong preferences for particular types of prey are evident. Diet is thus determined by the combination of preferences and the regional and seasonal availability of various type of prey. Gadoid fishes dominate the diet at least from late autumn through the spring in many areas, with polar cod (Boreogadus saida) being the most commonly consumed species. This small fish occurs both in ice-free and ice-covered waters, especially at the ice edge, with young polar cod sometimes living in spaces within the sea ice. Other gadoid fish are also seasonally important in some areas, such as Arctic (Arctogadus glacialis) and safron (Eleginus gracilis) cod and navaga (Eleginus nawaga), as well as redfish (Sebastes sp.), capelin (Mallotus villosus), smelt (Osmerus sp.) and herring (Clupea sp.). Invertebrates, both crustaceans and cephalopods, become more important in most areas during the open-water season. Ringed seals around Greenland live mostly in the ice-filled regions of North and East Greenland, where the bulk of the diet is polar cod and parathemisto (a kind of amphipod - see picture).
|Left: A ringed seal stomach cut open and revealing a full content of Themisto, of which a fresh specimen is shown on the right. Photos: Pinngortitaleriffik|
There seem to be age- and sex-related differences in prey composition. Adult ringed seals prefer to feed on pelagic schooling fish in most areas, while younger animals feed heavily on smaller prey such as amphipods and euphausiids. Adult females tend to eat smaller cod than adult males or juveniles.
Most ringed seal prey is small and preferred prey tend to be schooling species that form dense aggregations. Fishes are usually in the 5-10 cm range and crustacean prey in the 2-6 cm range, but larger prey may be taken on occasion. Typically, ringed seals prey upon no more than 10-15 species in any one area, with 2-4 species considered as important prey.
Ringed seals are the only Arctic seal that regularly maintains breathing holes in fast ice. They therefore occupy a vast area of habitat that is impenetrable to other seal species for much of the year. During the open water season and in areas of pack ice, they may occur with other seal species such as walruses (Odobenus rosmarus rosmarus), harp seals (Phoca groenlandica), hooded seals (Cystophora cristata) and bearded seals (Erignathus barbatus), and also whales such as belugas (Delphinapterus leucas), narwhals (Monodon monoceros) and bowhead whales (Balaena mysticetus). The diets of all these species, except for walruses and bearded seals, may overlap with that of ringed seals, and thus competition may be a factor affecting distribution and abundance in some areas.
Polar bears (Ursus maritimus) are by far the most important predator on ringed seals (e.g., Kelly et al. 2010, Kovacs 2014). Polar bears prey on little else but ringed seals, and commonly kill a seal every 2 to 6 days (Lydersen 1998, Reeves 1998, Rosing-Asvid, 2010; Iversen et al. 2013). They are approximately 26,000 polar bears in the Arctic, which take each year 100s of thousands of ringed seals (e.g., Stirling and Lunn 1997). They kill seals in their subnivean lairs by crashing through the snow roof, or take them at breathing holes. They also stalk seals lying on the ice in the spring and summer, in ice cracks and even in open water. Polar bears tend to be most successful at killing pups and sub-adult seals, but adult seals are also taken.
Ringed seals are the main prey for polar bears. Photo: flickr.com
Ringed seals are also preyed upon by walrus (Odobenus rosmarus), killer whales (Orcinus orca), glaucous gulls (Larus hyperboreus) and Greenland sharks (Somniosus microcephalus) (Lydersen 1998, Ridoux et al. 1998, Kelly et al. 2010b, Leclerc et al. 2012, Lydersen and Kovacs 2013). In addition, pups are taken by Arctic (Alopex lagopus) and red (Vulpes vulpes) foxes, wolves (Canis lupus), wolverines (Gulo gulo) ravens (Corvus corax) and dogs in the spring (e.g., Reeves 1998, Kelly et al. 2010b, Kovacs 2014).
|A walrus eating a ringed seal in Svalbard. Photo: M. Forsberg / Norwegian Polar Institute||
Ringed seal pup killed in it's lair by an Arctic fox. K.M. Kovacs and C. Lydersen / Norwegian Polar Institute
Although there is limited information on health parameters and disease for ringed seal (Tryland et al. 2006), they have been recently reviewed by Kelly et al. (2010b) and Kovacs (2014). Arctic phocids do not seem to have experienced any of the epizootic events with morbillivirus that have affected seals on the European coast. Many different parasites have been detected in ringed seals (Kelly et al. 2010 and Kovacs 2014 for review), the most commons being helminths in the gastro-intestinal tract. In Svalbard, the abundance of nematodes and acantocephalans in the digestive tract varies with sampling location and seal age and sex, influenced by the fish availability as prey and the age class exploited by the different seal groups (Johansen et al. 2010). Parasite burdens can be quite high in ringed seals, although they seldom debilitate healthy seals.