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[This information was originally produced by Beverly Skinner, wildlife biologist at Innoko
National Wildlife Refuge (in west central Alaska), for radio broadcast on Public Radio stations
Bear and Dog Ancestors
Scientists tell us that bears and dogs share a common ancestor. About 38 million years ago,
the bear and dog lines separated into two distinct groups. The bear group began to walk on the
soles of their feet while the dog group (called "canids" which includes modern day dogs, wolves and
foxes) continued to walk on their toes. As bears evolved into omnivores, which means they began
to include plant material in their diet, their gut became longer. Since plants take longer
to digest than meat, plant eating animals need longer guts than carnivores. The bears teeth
also changed over time. Canids tear their food when they eat, and have typical carnivorous
teeth - small pointed front teeth and pointed molars. But bears crush and grind their food
and therefore have short front teeth and rounded molars.
Bears differ from the canids in other ways too. We have all grown up with the story of how
when fall comes, the temperatures begin to drop and bears go into hibernation for the winter.
Hibernation is a way for animals to avoid many of the stresses of winter. But bears are not
true hibernators. Their body temperatures and heart rates do drop while in their winter dens
but if disturbed, unlike true hibernators such as arctic ground squirrels, bears may awaken.
It is during January and February of this winter dormancy period that the young baby bears
arrive. Born naked and blind, newborn cubs weight as little as a half a pound. But the young
cubs grow quickly underground in their winter den, feeding on their mothers milk which is rich
in fat and protein. As warmer spring weather approaches, mother and cubs emerge from their
winter shelter to resume their life above ground and their search for food.
For Alaska Naturally and the Innoko National Wildlife Refuge,
this is Beverly Skinner. Bears move to their winter
dens at different times in the fall depending on their age, sex and the weather. In some
areas of Alaska, during mild winters, bears may not move into a den at all. Be aware then,
especially in mild winters, that bears can and do emerge from their dens at any time. It
is a good idea to always follow safe and common sense bear practices even during the times
we assume all bears are asleep underground.
Note: This is the MapCruzin.com archive of the FWS Arctic National Wildlife Refuge website. In December, 2001 FWS took this website offline, making it unavailable to the public. It includes 90 plus pages of information and many maps. As of 2006 the important information contained in this, the original "unsanitized" version of the FWS website, has yet to return to the internet, so we will continue to maintain it here as a permanent archive to help inform activists and concerned citizens. If you find any broken links, please report them to me at [email protected] and I will attempt to make the repairs. January, 2008 update - A small part of the original information that was present in 2001 has made it back into the current ANWR website. There is also an archive that contains a small amount of the original information, but it is not readily available from the main website.
U.S. Fish and Wildlife Service. 2001. Potential impacts of proposed oil and gas
development on the Arctic Refuge’s
coastal plain: Historical overview and
issues of concern. Web page of the Arctic National
17 January 2001. http://arctic.fws.gov/issues1.html
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