Polar Bear (Ursus maritimus)

Polar Bear (Ursus maritimus)

Andrew Derocher, Canadian Wildlife Service.

© 2007, Canadian Museum of Nature. All Rights Reserved.


Polar bears, the largest land carnivores in the world, are found throughout ice-covered waters of the circumpolar Arctic. In Canada, there are 13 discrete populations, totalling approximately 15 000 bears. Polar bears are considered to be mainly marine animals and spend much more time on the sea ice than they do on land. They can swim several hundred kilometres without resting and can dive under water for up to one minute. In many areas of the Arctic, polar bears remain on the ice year-round. It is only in areas where the ice melts in the summer, such as Hudson Bay, that the bears are forced ashore until the ice refreezes in autumn.

Polar bears prefer to remain on the sea ice all year because they depend on a frozen platform from which to hunt seals. Without ice, the bears are unable to reach their prey: they seldom catch seals in open water. In the water, seals, with their sleek and powerful bodies, can easily outmanoeuvre polar bears. Polar bears hunt by ambush, waiting by holes in the ice for their prey to surface. In the spring when the ice begins to recede, they either retreat with it or move onto land. Staying with the ice means they will continue to have acc Read More

Polar bears, the largest land carnivores in the world, are found throughout ice-covered waters of the circumpolar Arctic. In Canada, there are 13 discrete populations, totalling approximately 15 000 bears. Polar bears are considered to be mainly marine animals and spend much more time on the sea ice than they do on land. They can swim several hundred kilometres without resting and can dive under water for up to one minute. In many areas of the Arctic, polar bears remain on the ice year-round. It is only in areas where the ice melts in the summer, such as Hudson Bay, that the bears are forced ashore until the ice refreezes in autumn.

Polar bears prefer to remain on the sea ice all year because they depend on a frozen platform from which to hunt seals. Without ice, the bears are unable to reach their prey: they seldom catch seals in open water. In the water, seals, with their sleek and powerful bodies, can easily outmanoeuvre polar bears. Polar bears hunt by ambush, waiting by holes in the ice for their prey to surface. In the spring when the ice begins to recede, they either retreat with it or move onto land. Staying with the ice means they will continue to have access to seals but at lower rates of success as the melt progresses.

The Polar bear is an example of an animal which has evolved certain physical characteristics, as well as behaviour, that enable it to be well adapted to its environment. Its fur, teeth, and skull structure, for example, differ from that of the Grizzly Bear, which lives further south in warmer environments. Like many other animals, its specialized adaptations are important to survival in its habitat. However, these same adaptations may no longer be useful in the face of a changing habitat due to climate warming.

An examination of a mammal’s skull and jaw can provide information about its feeding behaviour. For example, the teeth reveal whether the animal is a herbivore, carnivore or omnivore. Moreover, the arrangement of the teeth shows how the animal brings food to its mouth and how it chews. The differences are immediately apparent when comparing the teeth of a carnivorous predator to its herbivorous prey. Predators have well-developed canines and sharp, pointy molars. Compared to carnivores, herbivores generally have more developed incisors and flat-topped molars. These traits stem from how the animal has adapted to its environment. Over time, carnivores thrived by feeding on meat. Their pointy canines were an advantage for holding and killing their prey, while their sharp molars enabled them to slice through meat and rip it from the carcass. Herbivores, on the other hand, have excellent incisors that they use to cut grass, leaves and branches and for grazing. Their flat molars are handy for chewing and grinding fibres. All mammals have specific teeth that are favourable for feeding on a particular type of food in a given habitat.

Mammals of the same family (e.g. mammals that are closely related) share very similar physical characteristics. Scientists study these characteristics closely to determine what distinguishes one species from another. This helps them understand how a species emerged and how it was able to adapt to its surroundings.


© 2007, Canadian Museum of Nature. All Rights Reserved.

Learning Objectives

• Examine the factors (natural and external) that affect the survival and equilibrium of populations in an ecosystem.

• Show that species evolve and survive because of their ability to adapt.

• State a prediction and a hypothesis based on available evidence and background information

• Explain why different ecosystems respond differently to short-term stresses and long-term changes

• Formulate hypotheses regarding the effects of modifying the interactions that occur within a given ecosystem.


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