Natural History Of Ursus Maritimus
Natural History of Ursus Maritimus
Salman Ahmad, L01
Ursus Maritimus, polar bear, is a species of placental mammals. Out of all the bears the polar bear is the largest, weighing up to 680 kilograms. Reaching reach body length of about 10 feet, this species is also known to be the largest predator on land. The shoulder height of polar bear can range from 4 to 5 feet. Polar bears are gender dimorphic. Polar bears have the shortest tail in comparison to other bear species. The oldest known polar bear fossil was discovered in Prince Charles Foreland in 2004 and is thought to be up to 130,000 years old (Lindqvist). Amongst all the bears, the polar bears have the largest an d sharpest canines. Their fur coat is heavily insulated. While other arctic mammals may shed their fur in order to obtain a lighter hue for summer, polar bears do not shed their fur. The fur on the foreleg of male polar bear is thought to be comparable to the mane of a Lion in which it is used to attract females (Stirling).
In terms of evolution it is thought that the family of Ursidae diverged from its carnivorous ancestors some 37 million years ago. The brown bear, Ursus Arctos, is the closest member of the family to Polar bear. The evidence of this is presented through DNA analysis. The DNA genome demonstrates that the polar bear and brown bear diverged as two separate clades half a million years ago. Interestingly, mitochondrial DNA shows that some groups of brown bear are closer to polar bears compared to other groups of brown bear. Comparing the fossil records of both the brown bear and polar bear shows that teeth of the polar bear changed significantly from its closest family member. Although the two are genetically separate groups, it is possibility for them to mate. What is also interesting is that brown bears have a small portion of polar bear genetic material indicating that mating between the two groups has taken place in the past (Matthew).
The family of Ursus Maritimus is found in the Arctic Circle and nearby land. There is an estimate of 20,000 to 25,000 species of polar bear living. There are 19 recognized subpopulations of the polar bear. The North American subpopulations of polar bears account for half the entire population of species (Matthew). Three of the subpopulations are declining at a rapid pace. Polar bears were heavily hunted in Norway and poached in Russia during 19th Century (Aars). Since a lot of ice is melting and more distance is being created between ice patches and land, the habitat of Polar Bears are becoming somewhat skewed. Less ice means less ice for hunting, since some bears find the seal by sniffing their dens in ice. There has not been a lot of studying done on Polar Bears so exact nature and population of species is not accurate (Chose).
Polar Bears are currently listed as an endangered species. With the ongoing phenomenon of global warming they are considered even more threatened (Eric). Polar Bears reside in the Arctic since that is where their diet is found. They are terrestrial species but can spend a great time in water swimming. Males and non-fertile females do not need to hibernate in the winter unlike the Brown Bear species. These white bears are great swimmers and are able to travel long distances for food. Their rivals are, Odobenus Rosmarus, the walruses (Markus).
They typically feed on bearded seal, Erignathus Barbatus, but are known to also feat on whale and whale carcasses (Chose). When their typical diet is not available they may eat anything in sight such as deer, fish, and birds. These bears do not eat the entire prey, usually carcass remains which may be eating by other bears or other animals. A recently acquired diet is snow geese and their eggs. This is due to the increase in snow geese population and as subtle migration to lands with geese. Larger males have a greater chance of mating. Pregnant polar bears have a denning period during the end of fall season. A female is able to give birth to up to five cubs in her lifetime. Cubs are about 2 pounds and range from 12-14 inches. After birth cubs are nursed in the dens until they range from twenty to thirty pounds and then they come out of their den. Cubs acquire information from their mothers (Mauritzen). While brown bears and other species of bears are territorial, polar bears are not. Polar bears are still hunt and stealth hunters in contrast to other bears. Polar bears are cautious beings and are likely to choose to escape rather than attack. Due to the fact species interaction with humans has been very limited and so data on behavior with humans is very limited (Stirling).
The sensory system of the Polar Bear is highly advanced as it can detect scent from about a mile away. They can track scents left by other polar bears. Polar bears have a lot of fat on their body and thick fur coat. The adipose tissue on their body can measure up to 5 inches. They have 42 teeth in their canines are the largest and sharpest amongst bears. This combined with their extraordinary scent make them great stalk hunters. Male members of the species seek fertile females through scent. Mechanisms of selection and mating calls are not certain (Mauritzen).
They have short and bulky claws in contrast to brown bears. This can be due to the need to grip heavy prey. Their feet are long which provided excellent propelling in water when they swim. Their paws are studded with soft papillae, which is an excellent feature for motion on ice surfaces. Two main concerns a polar bear faces is maintaining body temperature in cold environment and storing enough energy to last until the next meal, which can range from a week to month. They eat about 4 pounds of fat a day to harvest enough energy. Their stomachs can hold massive amounts of food weighing a fifth of its body mass (Marcus).