Pusa hispida

Geographic Range

Ringed seals ( Pusa hispida ) occupy a circumpolar distribution ranging from 35°N, to the North Pole. They are found in all of the seasonally ice covered seas in the Northern Hemisphere and are native to the Arctic Ocean. Distinct populations occur in the Baltic Sea, Lake Ladoga of the Russian Federation, Lake Saimaa in Finland and the Sea of Okhotsk near Japan. In the Atlantic Ocean, ringed seals may be found as far south as New Jersey and Portugal. They have also been found in the Pacific, south to Zhejiang in China and near California.

• Biogeographic Regions
• nearctic nearctic
  • native native
• palearctic palearctic
  • native native

• Other Geographic Terms
• holarctic holarctic

Habitat

Through much of their range, ringed seals do not come ashore. Instead they inhabit arctic waters and are commonly found with ice floes and pack ice, which is used for resting, pupping and molting. They prefer large floes (>48 m in diameter) and are commonly found in the interior ice pack where the sea ice coverage is greater than 90%. Ringed seals tend to inhabit areas near the breathing holes they create or ice cracks, in order to escape predation. In more southerly regions and in lakes Ladoga and Saimaa, ringed seals rest on rocks, island shores and offshore reefs when ice is absent. They are distributed in waters of nearly any depth during non-breeding or molting seasons. Ringed seals are believed to move south with sea ice advancement and north when ice declines in the spring. Their distribution is also strongly correlated with food availability.

• Habitat Regions
• polar polar

• Terrestrial Biomes
• icecap

• Aquatic Biomes
• pelagic pelagic
• lakes and ponds
• coastal coastal

Physical Description

Ringed seals are the smallest pinnipeds; they have small heads and short cat-like snouts. They possess a dark coat with silver rings on their back and sides and a silver belly. Their foreflippers have strong, thick claws. Pups are born with lanugo or a woolly coat of white insulating hairs, which they shed within three weeks. They weigh 4.5 kg at birth and double their weight within two months. The succeeding coat is slightly longer and finer than that of adults. This coat is dark gray dorsally with a silver belly and a few scattered dark spots on the ventral side. There are few, if any, rings dorsally. This stage is known as “silver jars”.

Ringed seals have five subspecies: Arctic ( Pusa hispida hispida ), Baltic ( P. h. botnica ), Lagoda ( P. h. ladogensis ), Okhotsk ( P. h. ochotensis ) and Saimaa ( P. h. saimensis ), all of which vary in size. The Arctic and Okhotsk ringed seals are between 1.1 to 1.5 m in length and weigh between 50 to 70 kg. Females are slightly smaller than the males. Baltic ringed seals are the largest subspecies, ranging between 1.5 to 1.75 m in length and weighing between 110 to 124 kg. Ladoga ringed seals are the smallest, weighing between 32 to 56 kg. Their longer whiskers and darker coats make them unique compared to the other subspecies. Likewise, their rings are lighter colored with light vein-like patterns. Some Ladoga individuals have a black belt around their body with indistinct rings and brown spots in warmer weather. Saimaa ringed seals measure up to 1.5 m and weigh between 45 to 100 kg. Most have a dark gray-black coat, but there is substantial variety.

• Other Physical Features
• endothermic endothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• male larger

Reproduction

Males maintain large, under-ice territories that encircle multiple female territories. This suggests a form of mate guarding. The above and below territories of females are larger than those of males with more overlap. Males will position themselves near the primary breathing holes of post-parturient females until they are receptive. During this time, males may share breathing holes with females. Rutting males exhibit territorial behavior and emit a strong scent from their facial glands that smells like gasoline. They often exhibit fresh wounds to the hindflippers from male aggression with the onset of breeding. Increased vocalization has been observed during the spring.

Ringed seals have restricted movement during the breeding season, as they are ice-bound. This limits gene flow within the species. Baltic, Saimaa and Arctic ringed seals may display strong fidelity to particular sites, but some studies suggest that Arctic ringed seals range over a wide area. Pinniped species tend to exhibit polygyny because of the high concentration of estrus females. However, ringed seals circumvent this to a certain extent by aquatic, under-ice breeding.

• Mating System
• polygynous polygynous

Ringed seals breed from April to May. During this time, breeding seals occupy pack ice instead of the preferred shorefast sea ice, which is likely due to the distance from the shore rather than the type of ice. In addition, breeding sites may be selected based on prey availability. Pups are born in late winter or early spring, females give birth to one pup annually. On average, pups weigh 10 pounds at birth. They are nursed for roughly two months, during this time they double their weight. Their lactation period, which ranges from 5 to 7 weeks, is the longest lactation period among family Phocidae . During this time, mothers move young pups between her lairs (commonly 4 to 6 lairs per female). When the pups are older, this allows them to move independently between shelters if attacked.

Most females breed within a month of giving birth, but embryo implantation is delayed until mid-July or early-August. This means that their pregnancy lasts about 11 months. Traditionally, ovulation first occurs at 5 to 6 years of age, but since 1999, the average age of sexual maturity among female ringed seals has decreased to an average of 3.2 years. Females usually produce pups when they are between 6 and 8 years of age. Males typically do not participate in breeding until 8 to 10 years of age.

• Key Reproductive Features
• semelparous semelparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• viviparous viviparous
• delayed implantation delayed implantation

Most ringed seals give birth in subnivean lairs. These lairs are essentially snow-covered caves on ice floes that accumulate upwind and downwind of ice ridges or in cavities between ice blocks in pressure ridges. Adult females build lairs above breathing holes; this is a unique birthing habitat, which only ringed seals use. These lairs offer thermal protection to the pups against wind chill and cold weather and minimal protection against predators. During this subnivean period, mothers spend nearly 50% of their time in the water. Mothers may take pups in the water, but they need to return to the lair after a short duration because of the cold environment. Swimming is taught by the mother within the first week of life. Pups are weaned after two months, usually concurring with ice breakup, during which they gain weight and blubber. Afterward, the pups must learn to feed themselves, often loosing the blubber they had gained.

• Parental Investment
• precocial precocial
• female parental care female parental care
• extended period of juvenile learning

Lifespan/Longevity

Individual ringed seals have been known to live up to 43 years, but normally range from 15 to 28 years. Little is known about ringed seals in captivity or what limits their lifespan beyond predation. Pups are quite vulnerable to predation, Smith and Lydersen (1991) showed that Arctic foxes dug into 46% of the studies birth lairs and successfully killed 18% of the pups in Svalbard.

Behavior

Seals in the Baltic Sea, Lake Saimaa and Lake Ladoga display similar seasonal patterns to other ringed seals, however, they are forced to haul out on islands and shores during the summer when ice is absent. Ladoga ringed seals have a unique social structure by forming large herds during the open water period with mass haul outs.

• Key Behaviors
• natatorial natatorial
• motile motile

Home Range

The home range size of ringed seals varies seasonally and based on gender. Adult males tend to keep a home range size of 1 to 13.9 km2, whereas adult females maintain a 1 to 27.9 km2 home range. During the winter months, when their movement is restricted due to ice, they may travel no more than 1 to 2 km2. In the summer, they may travel up to 1,800 km2 away from their winter home ranges.

Communication and Perception

All pinnipeds have limited auditory systems due to their amphibious nature, as a result, they cannot produce or receive highly developed, acute, aquatic, high frequency sounds. Instead, they have advanced visual, tactile and passive listening skills, which aids in foraging, navigating and evading predators. Underwater, pinnipeds produce a wide variety of signals including whines, grunts, roars, chirps and pulsed sounds related to social behavior and reproduction. Ringed seals use sound cues to find holes in the ice, which helps them develop conceptual maps of the area under the ice.

• Communication Channels
• visual visual
• tactile tactile
• acoustic acoustic

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

Food Habits

Ringed seals have a generalist diet, exploiting prey based on availability including a variety of fishes, crustaceans , cephalopods , amphipods , euphausiids , mysids and shrimp, however, a few target species dominate seasonally. Their important prey species typically aggregate. In northeastern Greenland, Labansen et al. (2011) found their autumn diet was comprised of the small crustacean, Parathemisto libellula , while their spring diet was composed of polar cod and a few invertebrates. Seals from northwestern Norway also consumed polar cod in the spring, followed by fishes from families Stichaeidae and Cottidae . Other members of the cod family are important during the summer months in Alaskan waters including arctic cod and saffron cod .

Their coastal diets have a greater diversity of fish during autumn and spring than open water seals, which exploit mostly crustaceans. Ringed seals appear to prefer fish over crustaceans, even when P. libellula is most abundant. Young seals feed on a higher portion of crustaceans than adults. Ringed seals reduce their feeding during the spring molt. In the fall, prey availability determines breathing hole locations because at this time seals deposit fat for the winter.

• Primary Diet
• carnivore carnivore
  • piscivore piscivore
  • eats non-insect arthropods

• Animal Foods
• fish
• aquatic crustaceans
• other marine invertebrates

Predation

Ringed seals are primarily predated upon by polar bears , arctic foxes , and humans . Polar bear predation decreases with increasing snow depth and the thickness of lair roof coverings. Inuit hunters often attack structures that are near ice ridges. The ridge height and snow depth influences human success. The presence of “tiggak”, or the rutting male odor of ringed seals, lowers the chance of predator attacks. Field studies in Canada have shown that, on average, a polar bear in the High Arctic kills 43 ringed seals a year. An estimated 47% of those killed are pups caught in April to May, while 30% are newly weaned pups killed from June to July. Arctic foxes commonly scavenge the remains left by polar bears. Approximately 26.1% of pup predation occurs in their subnivean birth lairs. Foxes do not prey on adults. Pups born in exposed areas outside of lairs are especially vulnerable to avian predators, primarily glaucous gulls . This limiting of lairs may be a primary limiting factor of their southern breeding ranges.

Ringed seal pups have a prolonged white-coat stage and develop diving skills at an extremely young age. An estimated 50.3% of their time is spent in the water and they use multiple breathing holes to avoid predation. Adults establish breathing holes in landfast ice as ice forms in autumn, which is then maintained by the seals heavy claws. With accumulating snow, ringed seals excavate their lairs above breathing holes. They are never far from a breathing hole while on ice and use them as a primary escape method from predators in addition to maintaining multiple lairs.

Ecosystem Roles

Ringed seals are important in the diets of polar bears , arctic foxes and humans. They have also co-evolved with numerous parasites and diseases, such as the distemper virus.

Economic Importance for Humans: Positive

The Marine Mammal Protection Act of 1972 protects ringed seals from harvest with the exclusion of subsistence harvest by Alaskan native hunters. Quotas and licensing for harvest has been in place throughout the Russian Federation for decades. Alaskan natives use ringed seals for food and oil. The oil is important in different foods and is traded inland. They often use this oil on bearded seals' skins and sinews while sewing boat covers to make the stitches waterproof. Ringed seals' skin are used for clothing, equipment and crafts. Harvests of the hispida subspecies may be substantial in many northern coastal communities, but it has been deemed sustainable.

• Positive Impacts
• food food
• body parts are source of valuable material

Economic Importance for Humans: Negative

There are no known adverse effects of ringed seals on humans and they do not cause significant economic costs. However, ringed seals and humans indirectly compete for prey resources such as walleye pollock , Pacific cod , herring and capelin . There has been significant commercial harvest of ringed seals in the Sea of Okhotsk and predator-control harvests in the Baltic Sea and Lake Ladoga in the past, but this is currently restricted.

Conservation Status

Ringed seals are identified as 'least concern' according to the IUCN Red List, due to their broad distribution and numerous populations. However, they will need to be carefully monitored due to risks brought on by climate change. If a large amount of ice habitat is lost, ringed seals will be negatively impacted during pupping and rearing of young. Insufficient ice results in poor pup conditions and higher mortality rates. However, they are not considered depleted under the Marine Mammal Protection Act.

Baltic ringed seals are increasing at their primary breeding sites, but recent population-wide declines have occurred, along with current declines in some of their range. Ladoga and Saimaa ringed seals are probably the most threatened subspecies. Ladoga ringed seal have declined substantially in recent decades, primarily due to by-catch mortality in fishing gears and climate change. Saimaa ringed seals have an extremely small population that faces by-catch mortality. In recent years, they have suffered virtually complete reproductive failure, due to poor ice conditions within their range. The U.S. Federal list considers this subspecies endangered. On the other hand, Okhotsk ringed seals have not been censused since the late 1960’s, so population numbers and trends are unknown. However, as of February 26, 2013, the National Marine Fisheries Service considered the Arctic, Okhotsk and Baltic subspecies threatened, while the Ladoga subspecies is considered endangered under the Endangered Species Act. The proposed protective regulations are not in effect because the primary threat is habitat alteration arising from climate change.

Other Comments

The ringed seal has varied between the genus names Pusa and Phoca in recent decades. Most literature now accepts the name Pusa but it is not universally accepted.

Additional Links

Encyclopedia of Life

Contributors

Rebekah Spicer (author), Northern Michigan University, John Bruggink (editor), Northern Michigan University, Leila Siciliano Martina (editor), Texas State University.

References

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