Bear Necessities
Humans are widespread on our planet. There are
many of us, and we can survive in environments as
widely different as hot deserts, open plains, tropical
jungles, and the cold of Canada's Arctic. In all of those
environments, the presence of humans has an effect
on other living things and the way they interact with
each other and the environment. The study of
relationships between living things and between living
things and their environment is called ecology. A
Canadian example of the effects of humans can be found in the lives of the polar bears that
live on and around Hudson Bay.
The Bears of the Bay
Since the glaciers of the last ice age retreated thousands of years ago, the polar bears of
Hudson Bay have lived much the same way. In the winter they live on the ice of the bay. In the
summer they live in more southern forests. Bears and humans have always had trouble getting
along. We tend to live in the same places and eat similar things. Our niches overlap. An
ecological niche is the way of life or role of an organism. However, until relatively recently, the
only humans the polar bears would encounter were the Inuit and other Native peoples of the
north who did not create landfill sites. The town of Churchill, Manitoba, has a landfill site. The
town is also directly on the migration route of the polar bear, as you can see in Figure 1.
Polar Bears in Winter
The polar bear is not like other bears. In the
winter, while other bears are sleeping, the polar
bear is most active. Early in October, polar bears
begin migrating north onto the ice floes forming
on Hudson Bay. From freeze-up to breakup,
polar bears feed mostly on ringed seals and
bearded seals. The bear uses the high-energy
seal meat to build a layer of fat.
Polar Bears in Summer
As the ice begins to melt in the spring, the polar bears
move to the land and south to their summer retreat.
During the summer, polar bears live in the forest. They
spend most of the summer sleeping and lazing around,
living off stored fat. By the time temperatures begin to
drop in the fall, the bears have used up the energy they
stored as fat the previous winter. The hungry bears
begin moving north--and come to the landfill site in
Churchill, the fast-food restaurant on the bear migration highway. Unfortunately, a trip to the
garbage dump brings the bear into contact with humans. Hungry bears and angry humans are
a bad mix--one or the other may get hurt.
Understanding Concepts: Answer the following in your Science notebook:
1. Ecologists insist that no organism lives alone. How do polar bears interact with other living
things? How are bears affected by humans?
2. Why is the polar bear considered to be a marine mammal?
3. The polar bear lives in two different environments at different times of the year. Compare
the two environments in a chart. Include factors such as temperature, wind, and amount of
sunlight.
4. Only about 30% of a black bear's diet is made up of animals (insects, eggs, fish, and small
mammals). The other 70% is vegetation. Like humans, bears are classified as omnivores.
Explain how the diet of black bears could bring them into conflict with humans.