RINGED SEAL

 

The ringed seal (Pusa hispida) is an earless seal inhabiting the Arctic and sub-Arctic regions. The ringed seal is a relatively small seal, rarely greater than 1.5 metres (5 ft) in length, with a distinctive patterning of dark spots surrounded by light gray rings, hence its common name. It is the most abundant and wide-ranging ice seal in the Northern Hemisphere, ranging throughout the Arctic Ocean, into the Bering Sea and Okhotsk Sea as far south as the northern coast of Japan in the Pacific and throughout the North Atlantic coasts of Greenland and Scandinavia as far south as Newfoundland, and including two freshwater subspecies in northern Europe. Ringed seals are one of the primary prey of polar bears and killer whales, and have long been a component of the diet of indigenous people of the Arctic.

Ringed seals are the smallest and most abundant member of the seal family that live in the Arctic and Sub-Arctic regions. The average life span of a ringed seal is 40 years, with a solitary lifestyle and a diet based mainly on Arctic cod and planktonic crustaceans. Their main predators are polar bears. Recently, the biggest threat to ringed seals has been the changing temperature in the Arctic and the detrimental changes to sea ice that follow. With declines in snowpack and sea ice due to warming ocean and atmospheric temperatures, survival has become tougher for ringed seals in the Arctic and Sub-Arctic regions. Yet ringed seals are also potentially projected to thrive due to warming, considering the early extinction of their predators.

Sub Species

The populations living in different areas have evolved to separate subspecies, which are currently recognized as:

 P. h. hispida, in the Arctic basin; 

P. h. ochotensis, in the Seas of Okhotsk and Japan; 

P. h. saimensis, in Lake Saimaa; 

P. h. ladogensis, in Lake Ladoga; and 

P. h. botnica, in the Baltic Sea; all of which vary in size.

The arctic and Okhotsk ringed seals are between 1.1 to 1.5 m in length and weight between 50 to 70 kg. Females are slightly smaller than males. Baltic ringed seals are the largest sub species, 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 sub species. Likewise, their rings are lighter colored with light vein-like patterns. Some Ladago individuals have 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 a substantial variety.

Distinctive characteristics

Ringed seals resemble harbor and spotted seals, but are decidedly plumper (axillary girth may reach 80% of length). They also have a smaller, somewhat rounded head and muzzle, and a conspicuously short and thick neck. The muzzle is short, slightly broader than thick, and blunt. The vibrissae are light-colored and beaded. The eyes are relatively large and conspicuous. More than in other northern phocids, the size of the head and muzzle, and the close-set, forward-facing, eyes impart a cat-like appearance. The fore flippers are relatively small and slightly pointed, as in the harbor seal.

The background coloration is variable, but normally is medium to dark gray above and light gray to silver below. Ringed seals are conspicuously marked with light gray to off-white rings that encircle “spots” of the darker dorsal and lateral background pelage coloration. The spots are the same color as, or slightly darker than, the background color of the coat. Some ringed seals can be so heavily marked that many rings and spots fuse creating a confused paint-splattered appearance. The lighter colored sides have a variable number of dark spots that do not appear to be encircled by rings because of the paler lateral and ventral pelage. Pups are born with a woolly, thick, whitish lanugo. Fur of the succeeding coat is finer and slightly longer than that of adults, and is dark gray above, merging to silver below. There may be a few scattered dark spots on the undersides of these juveniles, and few, if any, rings on the back. At this stage, they are known as “silver jars.”

Dental formula    I 3/2, C 1/1, PC 5/5.

Size

Adults are up to about 1.5 m (5ft) in length. Weight is 50-70 kg, with a maximum of 110 kg. Pups average about 60-65 cm and 4-5 kg at birth.

Life Span

Average Life span in both Male and Female live up to 15-28years; Individual Ringed seals have been known to live up to 43 years.

Gestation Period    335 days.

Can be confused with

Ringed seals share their extensive range with seven other phocids. They are not likely to be confused with bearded, harp, hooded, gray or ribbon seals because of differences in size, coloration, and head shape, but care may be required to positively distinguish them from other seals with rings, spots or spot-like markings, such as harbor and spotted seals. Separating these species requires paying attention to coloration and markings, noting the relative size and shape of the head, and to the overall body size and shape.

Spotted and harbor seals are very similar in build and length. Adults of both are longer than ringed seals, and the neck, head and muzzle appear proportionately longer than in ringed seals. Spotted seals breed on sea ice and give birth to pups in a longer grayish lanugo coat like ringed seals. However, most spotted seals have no rings, and when they do they are usually only evident on the most heavily spotted individuals. Spotted seals have their pups on the surface of the ice, whereas ringed seals have their pups in lairs under snow layers on sea ice, and inside pressure ridges.

Harbor seals on land do not pup on sea ice, and do not regularly use ice except in areas where glaciers discharge ice into bays and fjords and it is a semi-permanent feature. Except in rare cases or when pups are born prematurely, the coloration of harbor seal pups is essentially the same as in adults and sub adults. Harbor seals generally have some rings, but when present, always have a mixture of rings and spots and are far less uniformly marked with rings than most ringed seals.

Distribution

Ringed seals have a circumpolar distribution throughout the Arctic basin, Hudson Bay and Straits, and the Bering and Baltic seas. The distribution of ringed seals is strongly correlated with pack and land-fast ice, and areas covered at least seasonally by ice. Adults use land-fast ice for breeding, molting, and over-wintering habitat.

Ecology and behavior

Nearly all ringed seals breed on the fast ice. Females excavate lairs in snow, in pressure ridges, and other snow-covered features. These lairs have access to the water, and provide camouflage and some protection from polar bears, which are the chief predator. Pupping generally occurs from March through April, and earlier in the Baltic Sea. Males are thought to be territorial, and possibly annually monogamous.

Many adults remain in the same localized areas year-round. Out of water, ringed seals are generally wary, regularly scanning for predators, such as polar bears and humans.

Predation

Polar bears (Ursus maritimus) are by far the most important predator of ringed seals. They kill seals at their breathing holes or in their subnivean lairs (i.e. lairs in the area between the surface of the ground and the bottom of the snowpack) by crashing through the snow roof. 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 also preyed upon by walrus (Odobenus rosmarus), killer whales (Orcinus orca), glaucous gulls (Larus hyperboreus) and Greenland sharks (Somniosus microcephalus). 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.

Feeding and prey

Ringed seals consume a wide variety of small prey, including many species of fishes, and planktonic and benthic crustaceans. These opportunistic feeders are known to have over 72 different species in their diet. In deep water, they forage in the water column and along the underside of ice floes, while in shallow water they often forage along the bottom with polar cod being a preferred prey species. Ringed seals forage either singly or in small groups.

Exploitation

Ringed seals reside within 35°N and the North Pole, and are thus known as a circumpolar based species. Climate change is projected to affect both Polar Regions more than anywhere else. This means a changing climate and life for all those residing in these Polar Regions. As for ringed seals, two potential outcomes lie ahead in this ever-changing climate.

In the past decade, the Arctic region has faced some of its highest temperatures within the instrumental record. Furthermore, within the past 2000 years, summer temperature highs have never been harsher, based on paleo-climate reconstructions. This warming is due to climate feedback mechanisms based on sea-ice melt. As sea ice melts, it frees up more open ocean water to be further heated, thus bringing about a positive feedback. Ocean water retains more heat than sea ice; additionally the albedo of sea ice is much higher than that of ocean water. Ringed seals require sea ice to live and reproduce. They live most of their lives alone, only grouping together into colonies when they are on sea ice to molt, mate, or rest. Without access to sea ice, ringed seals are unable to sustain life, which further affects trophic levels both above and below. Ringed seals are both predators and prey. A predator to zooplankton and fish, the ringed seal is considered a primary consumer as well as a secondary consumer. But the tertiary consumer, or top predator, in the Arctic is the polar bear, feeding mostly on seals, including the ringed seal. Yet through further exploration, the potential fates of this Arctic food web seem to be ambiguous, leading to a very important trade off of polar bear mortality and ringed seal sustenance.

Threats and status

The vast geographic range occupied by ringed seals, coupled with their solitary nature and the difficulties of conducting population assessments in remote polar areas, make it difficult to estimate ringed seal population levels. Estimates of the world-wide population range from 4 to 7 million, with most authors expressing caution over the accuracy of both local area and range-wide figures. P. h. saimensis, of Lake Saimaa, Finland, and P. h. ladogensis, found in Lake Ladoga, Russia, are both restricted to only these land-locked bodies of water, and occur in very low population numbers (approximately 200 and 5,000 respectively).

Native peoples of the Arctic hunt ringed seals for food and skins, and have done so for thousands of years. Direct human interaction and conflicts are otherwise minimal. Existing subsistence harvests, and the commercial use of skins from some of these harvests, such as occurs in Greenland, do not appear to be negatively affecting any ringed seal populations. Most ringed seals take few commercially important prey species, with notable exceptions in Greenland and in the White and Barents seas. The Baltic Sea population, P. h. botnica, is surrounded by large human population centers and may suffer from exposure to pollutants that compromise their immune system and lead to higher rates of disease that negatively affect reproduction.

The effects of global warming and the projected decreased extent and duration of sea ice cover associated with warming of the Arctic could have dire consequences for ringed seal survival. Several studies have already demonstrated decreased reproductive success in response to poor sea ice conditions in localized areas.

The estimated population size for the Alaska stock of ringed seals is 249,000 animals. In 2010 the trend in numbers for this population was unknown. Ringed seals are listed as a species of "least concern" by the IUCN and were considered 'not threatened' under the Endangered Species Act in 2006. Reliable estimates of the minimum population, potential biological removal and human-caused mortality were not available in 2006. The level of annual U.S. commercial fishery-related mortality or injury was considered insignificant. The Alaska stock of ringed seals is not considered a strategic fishery stock. In 2008 the US National Marine Fisheries Service began a conservation status review under the Endangered Species Act (ESA) to determine if listing this seal under the ESA is warranted.

Factors hypothesized include

The direct and indirect effects of large-scale commercial fisheries on key prey species, long –term ecosystem shifts, and changes in behavior by a primary predator, the killer whale, or a combination of these factors.

IUCN status    Least Concern

Before surfacing, ringed seals sometimes blow bubbles up their breathing hole to check for polar bears, their main predator.

Skin Of The Ringed Seal