The Brown Bears in ANWR
General Characteristics
-Brown bears, along with polar bears, are the largest of the bear species.
Brown bears range in weight from 90 to 800 kg (200 to 1760 lb), and adult
males generally weigh more than adult females.
-Grizzly bears, with a diet of berries, vegetation, and small mammals, are
smaller than Kodiak bears.
-the average weight of grizzlies varies from 150 to 360 kg (330 to 794 lb) in
Alaska(1)
Reproduction
-Females have their first young at five to seven years old. They normally give
birth to two cubs, skipping three to four years between litters. They can
reproduce until almost 30 years of age, but few survive beyond the age of 20.(1)
-Brown bears escape the Refuge's long winters by hibernating for up to eight
months each year. During this long sleep, bears do not eat or drink. They do,
however, give birth and nurse their cubs.
Food
Outside the den, brown bears explore widely for foods that are often in short
supply. While spring snows remain, bears eat carrion, ground squirrels, and
roots. In early June, some bears, especially sows with young, prey on newborn
caribou. This opportunity lasts only a few weeks, until the calves are too
nimble to catch. During the summer, brown bears feed mainly on greens. Some
search high into the mountains for new growth emerging from late-melting
snows. Later, the bears consume large quantities of berries. When snows
return, often by mid-September, the bears again dig for ground squirrels and
roots. (1)
Places to Live
Most Refuge brown bears den in the mountains south of the coastal plain.
Because the Refuge is underlain by permanently frozen ground, bears select
rock caves, or sandy soils that have thawed more than four feet deep. The
soils can collapse easily unless the top four inches are frozen, so bears must
wait, usually until mid-October, for a hard freeze before excavating their
dens. (2)
Population
Brown bears on the Refuge are faced with a long winter hibernation and limited
food resources. As a result, they have small bodies, low reproduction rates,
and slowly maturing young. This northernmost population has remained
remarkably stable, however. The only enemies these monarchs have are old age,
other brown bears, and occasionally man. (2)
References
1) http://encarta.msn.com/encyclopedia_761579742/Brown_Bear.html
2) http://www.r7.fws.gov/nwr/arctic/bears.html
costiner"at"mit.edu
Last updated: Nov 12,
03