Siberian Polar bear (Profile) Feb 26, 2011 20:21:28 GMT -9
Post by grrraaahhh on Feb 26, 2011 20:21:28 GMT -9
Siberian polar bear
Ursus maritimus marinus Pallas, 1776
A detachment of Prey - Carnivora
Bear family - Ursidae
Status. Category 3. A rare subspecies of white bears.international measures to protect the species.
Distribution. The polar bears are unevenly distributed within the limits of the range because of irregular distribution of the seals. However in spite of the spatial-temporal variability some leading principles can be distinguished in the distribution of animals in the Russian Arctic. The most general principle is that the population density decreases from the western and eastern regions towards the central one.
Knottnerus-Meyer (1908) distinguished 6 forms of the polar bear. He considered each of them to be a separate species. Further investigations (Ognev, 1931; Birulya, 1932; Bobrinskiy et al., 1965; Geptner et al., 1967) showed all the polar bears to belong to one species though subdivided into several subspecies. Other authors (Vereshchagin, 1969; Chernyavskiy, 1969; Uspenskiy, 1989), contrary to the previous ones, stated that geographical variability is not pronounced in the polar bear.
The polar bears are met more often near the Wrangel and Gerald Islands, Long Strait and in the southern part of the Chukchi Sea in winter and in spring.
In summer and in early autumn the bears are dispersed along the southern edge of the drifting ice. They are met in the mainland, in the Wrangel and Gerald Islands rather rarely over this period. In the middle of autumn and in spring seasonal migrations and breeding take place, so the animals are met much more frequently in these regions. 1285 bears were observed at the Wrangel Island in the period from 1979 to 1984. 87.2% of them were met in spring, 9.4% in autumn, 3.4% in summer and 3.4% in winter (Belikov et al., 1986).
The highest density of the polar bears' population is recorded in the eastern region of the Russian Arctic (0.72 individuals per 1000 sq.km.). This is undoubtedly connected with the high density of pinnipeds there. The density of bears' tracks (number of footprints per 100 km) is connected also with the rate of ice breaking (characterized by the coefficient of disintegration) (Shilnikov, 1973). Thus, special tracking of polar bears conducted in the Chukchi Sea and in the eastern part of the Eastern Siberian Sea in the period from 1982 to 1984 has revealed great variability in the density of footprints (from 0 to 35.7). The highest density of the tracks has been observed in the areas with the greatest ice disintegration.
The main breeding grounds are a subspecies of Wrangel Island and Herald. Maternity dens are also found on the Chukchi coast. From the Chukchi Sea polar bears regularly penetrated by freezing and on drifting ice in the Bering Sea. In the spring, with the melting of the ice pack, solitary Polar bears sometime are found to the west, the Sea of Okhotsk coast of Kamchatka and in the river valley. Penzhina. Reported sightings around the Anadyr and eastern Kamchatka coast down to the northern Kuril Islands have been observed. When moving over land, the Polar bears fur becomes dirty gray and local northern Kamchatka reindeer herders refer to them as "irhuim" - a giant black bear. These Polar bears then migrate back in a northerly direction.
Credible registered cases of Siberian polar bears in Kamchatka.
THE NUMBER OF POLAR BEARS IN THE RUSSIAN FEDERATION
According to expert estimates, in the early 1990s the size of the polarbear populations inhabiting the Russian Arctic and the adjacent areas amounted to: the Kara-Barents population – 2500-5000 animals, the Laptev population – 800-1200 animals, the Chukotka-Alaska population – 2000-5000 animals. For the latter population, the estimate recommended by the Polar Bear Specialist Group of the IUCN Species Survival Commission is 2000 animals.
Based on the results of the polar bear census conducted in 2004 in the northern part of the Barents Sea, including the area of Svalbard and Franz Josef Land archipelagos, the size of the Barents Sea part of the Kara-Barents population was estimated at approximately 2650 animals.
Appearance & Weight. Sizes are very large. Average body length of males 2 m, occasionally to 3 m, females - 1,85 m, weight - 700 kg, but usually less. The body, neck and head much elongated, in contrast to the brown bear. Ears are short, rounded, slightly prominent fur. Limbs long, the soles are covered with dense hair. Claws large, slightly curved, dark-brown color. The tail is noticeably longer than the brown bear. The coat is very thick and dense, but short. Ear hair is shiny, almost white, usually with yellow tops. Underfur pure white. When moving overland fur bears become a dirty gray.
BIOLOGY OF THE POLAR BEAR AND PREREQUISITES FOR ITS CONSERVATION
The polar bear is an evolutionarily young species. It is thought that its modern phenotype formed between 250,000 and one million years ago. Most scientists studying the evolution of the species believe that the polar bear originated from a group of brown bears in the early or mid-Pleistocene. Initially, the ancestors of the polar bear supposedly fed on organic remains found in the littoral zone, gradually switching to active hunting of seals resting on the sea ice. Eventually, this process led to the evolution of an active predator capable of living on the sea ice throughout the year and well-adapted to extreme environmental conditions of the Arctic.
The polar bear is the largest land carnivore with adult males measuring up to 280 cm in length, and up to 160 cm in height at its shoulders. Males typically weigh 400-600 kg, although the weight of an adult male has reached 800 kg in some reported cases. Females are smaller and lighter (130-300 kg), however, the weight of a pregnant female going into a den may reach 500 kg.
Polar bears generally lead a solitary or solitary family (a female with her cubs) way of life, but may form large temporary groups associated with major sources of food. Typically, bears are not aggressive toward each other, although adult males may attack cubs.
According to zoo reports, the life span of polar bears rarely exceeds 25-30 years (the record life span in captivity amounted to 45 years). Females usually reach sexual maturity at 4-5 years, males at 6-7 years. The reproductive ability is retained until the age of 21. Courtship and mating take place from March to June; a breeding female may be followed by up to 3-4 males. In September and October, pregnant females come to denning areas – coastal mountain areas of the mainland and Arctic islands. The females begin to dig maternity dens when snow banks large enough are formed on the slopes, usually in October or November. The most significant denning areas in the Russian Arctic are located on Wrangel Island, Herald Island, and in such archipelagos as Franz Josef Land and Novaya Zemlya. The maximum density of maternity dens has been observed on Herald Island, reaching 12 per 1 km. The latent phase of pregnancy ends when the female goes into the den and active development of the embryo begins. Pregnancy lasts for a total of 230-250 days; cubs are born in December and January and most maternity dens are broken open between mid-March and mid-April. After opening of the maternity den, the family stays in the denning area for 2-4 weeks , with the mother helping the cubs get used to living outside the den and preparing them for the transition to the sea ice. During that period, family groups are particularly sensitive to disturbance factors.
Reproductive success of the species is determined, to a considerable extent, by denning conditions, including availability and quality of snow banks, the absence of disturbance factors, and availability of prey and stability of weather conditions after leaving the den. Polar bears are characterized by a low reproductive potential: females give birth once in two or three years, with one to three cubs in the litter. According to the studies conducted in 1970s on Wrangel Island, the average litter size at the end of the denning period was 1.79 (n=192); with the percentage of two-cub litters being 70.3%, one-cub – 25.5%, and three-cub – 4.2%.
Thus, a female is able to produce no more than 8-12 cubs during her lifetime. Cubs are born helpless, as in all bear species, weighing around 600g. Within three months after giving birth, the female and cubs leave the den, switching to a nomadic way of life on the drifting sea ice. In normal conditions, cubs stay with their mother until the third fall of their life. Mortality rate among first-year cubs amounts to at least 30-40%.
There is no data on the sex and age structure of the polar bear populations in the Russian Arctic. According to the available data on the bear populations in the foreign Arctic, the male to female ratio is about 1:1, the ratio of adult to young bears is also 1:1.
The peculiarities of the polar bear’s biology, including large body size, low fertility, the long period during which cubs stay with their mother, low genetic diversity and high mortality rate in young bears make the species ecologically vulnerable to major changes in the habitat conditions, which, in turn, may lead to a dramatic decline in the population sizes.
At the same time, polar bears are characterized by a highly adaptive behavior, well-developed basic intelligence, and a high enough level of ecological plasticity and social behavior (group use of major food sources), which makes it easier for the species to survive and improves the viability of the populations.
Measurements of the skull. Used the following measurements of the skull: 1 - the total length, 2 - condylobasal length, 3 - base length, 4 - the length of the brain, 5 - length of the facial department, 6 - facial length, 7 - the length of the palate bone, 8 - length of the upper dentition CI-M2, 9 - the length of the upper row of cheek teeth P4-M 2, 10 - zygomatic width, 11 - width of the crania, 12 - the smallest width of the skull (temporal width narrowing), 13 - interorbital width, 14 - in width occipital condyles, 15 - mastoiditis-width of 16 - the width of the bone palate with guttural cuttings, 17 - the greatest width of the bone palate, 18 - width of canines, 19 - the maximum diameter of the orbit, 20 - the height of the nape, 21 - the length of the mandibular bone, 22 - the length of the mandibular bone to the ridge of the angular, 23 - length of the lower dentition cl-TK, 24 - the length of the bottom row of cheek teeth p4-TOR 25 - the height of the mandibular bone in the coronoid process, 26 - the height of the mandibular bone behind ml, 27 - the height of the mandibular bone in the diastema.
Diet and Foraging Behavior
Like all large predators, polar bears need large amounts of food. The main prey of the bear is seals (ringed and bearded seals), which can be hunted from the ice only. Sometimes bears hunt walruses (mainly calves) and harp seals.
Above: Polar bear catches seal.
At the same time, polar bears are able to switch to alternative types of food relatively easily. When staying on the land, they may eat carcasses of dead animals, kelp, fish washed up on shore, and other vertebrate animals they are able to hunt. In some locations, bears feed on waste of animal harvesting activities carried out by humans. There were also known cases of polar bears feeding on seabird colonies.
When forced to come onto land in search of food, polar bears often travel large distances along the shore. During such travels they may encounter humans and become a victim of illegal harvesting or a forced kill.
Above: Polar bear and walrus carcass.
The ringed seal and bearded seal form the basis of the bear diet, though the bears would consume various foodstuffs in different regions. Other seal species are randomly consumed. 15 to 20 kg of food can be found in the stomach of one beast. 41 kg of the walrus meat has been found in the stomach of one particular bear (Tzalkin, 1936). This is considered to be a record.
The role of walrus in the polar bears' foraging is poorly studied. Lono (1970) noted that walrus was a rather rare prey of the bears in Spitzbergen. This may be due to the low density of the walrus population on the island. 77 stomachs have been examined. 42 of them (54.5%) appeared to be empty, 13 of them (16.9%) contained the remnants of ringed seals and 1 (1.3%) contained the remnants of bearded seals. In 4 stomachs (5.2%) the remnants of other seals have been found (species were not determined). Remnants of polar bears have been found in 3 stomachs (3.9%), sea weed in 12 stomachs (15.6%) and land plants in 1 stomach (1.3%). Tzalkin (1936) studied the stomach contents of 145 bears harvested near the Franz Josef Land in summer. 64 stomachs (44.2%) were empty, 55 of them (37.9%) were filled with the remnants of ringed seals. The remnants of walrus were found in 18 stomachs (12.4%), the remnants of bearded seals in 4 of them (2.7%), sea weed in 3 of them (2.1%) and the remnants of birds in 1 stomach (0.7%). The author considers walrus meat to be an occasional foodstuff that remained from carcasses abandoned by hunters. So the walrus play no significant role in the foraging of the polar bears.
Above: Polar bear (Ursus maritimus),
eating walrus, Wrangel Island.
Terrestrial mammals are undoubtedly an occasional prey of the polar bears. Pedersen (1945) has observed a few cases of bears' preying on musk oxen (Ovibos moschatus) and reindeer (Rangifer tarandus) in north-eastern Greenland. Polar bears have been seen several times near grazing reindeer in Spitzbergen (Lono, 1970). The beasts made no attempts to attack the ungulates. The polar bears prey sometimes on voles and lemmings on the mainland; on the coast of Hudson Bay they succeed occasionally in catching a muskrat (Ondatra zibethica) (Russel, 1975).
Lutzuk (1978) reports on the mass consumption of dead chicks of the thick-billed murre (Uria lomvia) under a rocky rookery in the Wrangel Island. In the Bennet Island (Novosibirskiye Islands) some bear faeces contained not only plant remnants but also the feathers and bones of birds (Uspenskiy, 1963). The bears would feed on the birds' carcasses at the foot of the rookeries. Studies of the bears' feces found on the Hucker Island (Franz Josef Land) have revealed the same phenomenon.
Residents of the Wrangel Island reported that great amounts of Arctic cod (Boreogadus saida) cast ashore are consumed sometimes by the polar bears. In some cases bears feed on 470
the carcasses of dead conspecifics (Urvantzev, 1935; Tulin, 1938; Rutilevskiy, 1939). The Russian Arctic is involved nowadays in broad-scaled industrial exploitation. The increase of anthropogenic impact on the ecosystems may result in the exhaustion of the bears' food base. This will force polar bears to shift to the secondary foodstuffs, to visit slops pits at the dwellings of people, to destroy food stores and so on.
Habitats and lifestyles. Polar bear - sea beast. Habitats are vast fields of ice with divorce and polynyas, ice shore fast ice and the narrow edge of the coast of the Arctic islands and the mainland. Rarely comes into the land. The concentration of animals is more often observed at the edge of the drifting ice. Most of the time they wander or passively, with floating ice, or actively. Only females with young cubs are sedentary. Well adapted to survival in arctic conditions, possess great stamina. Very good swim and dive, often disposed of in open sea for tens of kilometers. Polar bear - an active predator. It feeds primarily pinnipeds (ringed seal, bearded seal and other species), fewer fish in the summer birds, their eggs, sometimes reindeer, Arctic foxes and rodents. In dens occur only pregnant females. By the coast of Wrangel Island, they usually come up in September - early October. Leave their dens with newborn cubs bears from early March to late April. Youngsters for a long time left with her mother and only after the age of 2-2,5 years of transition to independent living. Females produce the first litter at the age of 4-5 years, and then make then the set time in 3 years. Males participate in reproduction after the age of 5-6 years. Thus, the reproductive potential of the population is small.
After ice melting the polar bears that have spent the winter period in the Bering Sea migrate to the Chukchi Sea again. In the period from June to September most of the bears continue to move northwards. The south-eastern part of the Chukchi Sea is free from ice at this time. If the ice conditions are favorable in the eastern regions of the Arctic there is no ice in the Long Strait and sometimes in the whole area of the Chukchi Sea in August and September. Polar bears leave for the north and reach adjacent areas of the Arctic basin. Migrations are more intensive in the years of favorable ice conditions (when the ice is more disintegrated and crumbled than usual). Rapid ice melting forces the bears to move immediately towards the north.
In the Barentz, Kara, Laptev and East Siberian Seas bears' migrations are determined by the seasonal changes in ice conditions just as in the eastern regions. The polar bears would follow the withdrawal of the ice edge towards the boundaries of the Arctic basin. In the Barentz Sea the ice edge is located at a distance of 100 to 200 km to the north of Spitzbergen, Franz Josef Land and the Ushakov Island and does not shift from year to year.
In autumn pregnant females come ashore to lie down in the dens.
The time of the females' emergence on the land is noted to be connected with the ice conditions (Mineev, 1935; Romanov, 1941; Harington, 1968; Lono, 1970). If the ice conditions are favorable the females would travel towards the denning sites. They would stay in the seas under unfavorable conditions. It is worth mentioning that all the authors except Harington (1968) and Lono (1970) identify the time of bears' emergence on the land with the beginning of the denning period.
Number and limiting factors
At the end of 1970. the total number of species was estimated at 25 thousand individuals, including 5-7 thousand in the Russian Arctic. Currently, it has increased, and within Russia is determined to 12.7 thousand individuals. The number of dens on the island of Wrangell ranges currently in the range of 500-600, on the island of the Herald - 30-50. Limiting factors - fluctuations in climate, relatively low rate of reproduction of population, anthropogenic environmental pollution, poaching.
Although prior to the early 1990s the poaching of polar bears took place in the Russian Arctic, it was limited to individual cases of killing at polar stations, mines, or coastal communities. A person trying to transport skins from a hunting site and/or sell them would face serious difficulties at the time.
The year 1992 saw the beginning of a dramatic change in the situation. Since the mid-1990s illegal hunting of polar bears has become a widespread practice in certain areas, with the most significant poaching hotspots including Chukotka and Western Taymyr (around Dikson settlement). This conclusion is based on the information on the number of polar bear skins processed by taxidermists in large cities, on the number of skins offered for sale via the Internet, and on the results of surveys conducted in the indigenous communities of the Chukchi Peninsula.
Although there is no accurate data available on the exact number of polar bears illegally taken in the Russian Arctic and associated damage to the respective populations, experts believe that this figure is significant in terms of its impacts on the conservation of the populations.
Forced kills resulting from human-bear conflicts
The shrinking of the Arctic sea ice caused by the changing climate in the Arctic forces polar bears to move onto land more frequently. This leads to an increased probability of human-bear conflicts and forced kills.
Scientific and practical significance of preservation of the subspecies. Conservation of the Siberian population of polar bears, in addition to the aesthetic aspect is biocenotic value. In ecosystems, sea coasts, this species plays an important role in the circulation of organic matter.
The Polar bear had long been a traditional target species for coastal Chukchi and Eskimos. In the late XIX - early XX centuries. They annually produce at 100-300 animals, and only in 1920 and 1930. Harvest bear pelts dropped to 100-150.
Accepted and necessary protection measures. Listed in the IUCN Red List-96 and the Red Book of Russia. Since 1956, hunting of polar bears in the Russian Arctic are generally prohibited. From 1960 on the island of Wrangel a Regional Reserve, and from 1976 - Reserve, one of the main tasks is to protect and study polar bears. Must strictly adhere to security measures, monitor size, monitor the prevention of pollution of the environment, to implement agreed international measures to protect the species.
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WWF: Climatic change impact in the Russian arctic; link
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General Siberian Polar Bear discussion thread: shaggygod.proboards.com/index.cgi?action=display&board=siberianpolarbear&thread=446