Arctic ringed seals are in many respects the “classic” ice-seal. The subspecies P. h. hispida and P. h. ochotensis use sea ice exclusively as their breeding, moulting and resting (haulout) habitat, rarely if ever coming onto land (Smith and Stirling 1975, Frost and Lowry 1981, Kelly 1988). Their ability to create and maintain breathing holes in sea ice using the well-developed claws on their fore-flippers allows them to thrive in areas where even other ice-associated seals cannot reside. Although ringed seals are quite small they deal with 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. The lairs are particularly important for neonatal survival (e.g., Lydersen and Smith 1989). Each seal builds several lairs so that they can escape if a predator attacks one of their structures; ringed seals have co-evolved with their principal predator, the polar bear (Ursus maritimus) over the last tens of thousands of years (Stirling and Øritsland 1995). Arctic foxes (Alopex lagopus) are also an important predator in some coastal areas (Smith 1976, Lydersen 1998). In addition to the constructed holes and lairs, ringed seals also use natural cracks along pressure ridges and leads in the sea ice for breathing.

Reported mean age at sexual maturity (MAM) for ringed seals females varies in the literature from 3.5 – 7.1 years (Holst and Stirling 2002, Krafft et al. 2006). Males likely do not participate in breeding before they are 8 and 10 years old. The average size of adults 10 years and older varies between locations and different age cohorts, but averages of 115-136 cm in length and 40-65 kg in weight have been reported, with males being slightly larger than females (Smith 1973, Frost and Lowry 1981, Smith 1987, Lydersen and Gjertz 1987). Ringed seals are long lived, with ages close to 50 reported (e.g. Lydersen and Gjertz 1987). Reproductive rates of adult female ringed seals vary between 0.45-0.86 (see Reeves 1998), with a maximum of 0.91 (Lydersen and Gjertz 1987). Regional production rates are variable; reproductive success depends on many factors including prey availability, the relative stability of the ice, sufficient snow accumulation prior to the commencement of breeding, etc. (e.g., Lukin 1980, Kelly 1988, Smith 1987, Lydersen 1995).

A single pup, weighing 4.0-4.5 kg, is born in the spring (March to May), with most pups being born in early April (Frost and Lowry 1981). In Lake Saimaa and in the southern part of Baltic Sea pups are born somewhat earlier, in late February or early March (Pälsi 1924, Sipilä 2003). Births occur in subnivean lairs excavated in snow that accumulates upwind and downwind of ice ridges (Smith and Stirling 1975, Furgal et al. 1996), or in cavities occurring between blocks of ice in pressure ridges (McLaren 1958, Kelly 1988). Lairs provide thermal protection against cold air temperatures and high wind chill and afford at least some protection from foxes and polar bears (Smith 1976, 1980, Smith and Stirling 1975, Gjertz and Lydersen 1986). A female will move a young pup between lairs within her complex of lairs (usually 4-6 per female) if one lair is attacked by a predator; older pups are able to shift between structures independently as they develop swimming skills in the first weeks of life (Lydersen and Hammill 1993a,b). Lactation lasts an average of 39 days and pups are weaned at approximately 20 kg (Lydersen and Kovacs 1999). Females mate towards the end of the lactation period, similar to other phocid seals. Shore-fast ice is considered to be the most important habitat for pupping, although the importance of pack ice is not well known; this habitat is used at least in the Davis Strait and in the Barents Sea (e.g. Wiig et al. 1999).

Ringed seals moult from around mid-May to mid-July when they spend quite a bit of time hauled out on ice at the edge of the permanent pack ice, or on remnant land-fast ice along coastlines (Reeves 1998). Feeding intensity is at a minimum at this time (Ryg et al. 1990).

Outside the breeding and moulting seasons, arctic ringed seals are distributed in waters of nearly any depth; their distribution is strongly correlated with seasonally and permanently ice-covered waters and food availability (e.g. Simpkins et al. 2003, Freitas et al. 2008).

Many studies of the diet of arctic ringed seal diet have been conducted and although there is considerable variation in the diet regionally, several patterns emerge. Most ringed seal prey is small, and preferred prey tends 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. Typically, a variety of 10-15 prey species are found with no more than 2-4 dominant prey species for any given area. Fishes are generally more commonly eaten than invertebrate prey, but diet is determined to some extent by availability of various types of prey during particular seasons as well as preference, which in part is guided by energy content of various available prey (Reeves 1998, Wathne et al. 2000). Polar cod (Boreogadus saida) is often reported to be the most important prey species for ringed seals (see Labansen et al. 2007 for review). Young polar cod (≤2 yrs) are often found closely associated with sea ice, living under and even in spaces within sea ice (Falk-Petersen et al. 1986). Ringed seals also eat a variety of other members of the cod family, including arctic cod (Arctogadus glacialis; Holst et al. 2001), and saffron cod (Eleginus gracilis) with the latter being particularly important during the summer months in Alaskan waters (Lowry et al. 1980). Redfish (Sebastes spp.), capelin (Mallotus villosus) and herring (Clupea harengu) are also important in the diet of arctic ringed seals in some regions. Invertebrate prey seems to become more important to ringed seals in the open-water season and often dominates the diet of young animals (e.g. Lowry et al. 1980, Holst et al. 2001). Large amphipods (e.g. Themisto libellula), krill (e.g. Thysanoessa inermis) mysids (e.g. Mysis oculata), shrimps (e.g. Pandalus spp., Eualus spp., Lebbeus polaris, Crangon septemspinosa) and cephalopods (e.g. Gonatus spp.) are all eaten by ringed seals and can be very important in some regions at least seasonally.

Ringed seals in the Baltic sea as well as in Lakes Saimaa and Ladoga use ice for breeding and moulting, but are forced to haul out on islands and shorelines during the summer season when ice is not available. Their general season patterns are similar to those of arctic dwelling ringed seals. One notable difference in social structure is that Ladoga ringed seals form large herds during the open water period; this behaviour of mass haulouts is concentrated in the Valamm Nature Park (Agafonova et al. 2007).

Saimaa and Ladoga ringed seals are confined to freshwater lakes where they prey on a wide variety of fish and some invertebrates, especially smelt (Osmerus eperlanus), vendace (Coregonus albula), burbot (Lota lota), perch (Perca fluviatalis), roach (Rutilus rutilus), whitefish (Coreogonus lavaretus) and other fishes in small quantities (Sipilä and Hyvärinen 1998, Agafonova et al. 2007).