American Black Bear – URSUS AMERICANUS

As of 2012, the American Black Bear population living in the Sierra Nevada Mountain Range was at 10,000 bears. Mostly, they live at higher elevation levels, 3,000 feet and above, in areas managed by the U.S. Forest Service or the National Parks. There is about one bear per square mile.

A rough estimate of Nevada County’s high elevation habitat puts our bear population count at around 500 bears.

Coat Variation Colors:

Brown, cinnamon, yellow-brown, grey-blue and white


Full Grown Females: 100-200 pounds
Full Grown Males: 150-350 pounds


Ninety-five percent of a bear’s diet is plant-based.

They eat: acorns, manzanita berries, insects and sometimes grass. (Snag logs, left to decompose, are sources for insects and used as dens.)

Bears are omnivores, which means that they will eat whatever is available, including human garbage and pet food.


Excellent sense of smell
Good climbers
Avoids confrontation
Good swimmers


Female bear fertility is directly linked to nutrition and food availability. They must have high-quality berries and acorns to successfully reproduce.

Bears mate in June & July (females begin to breed at age four-and-a-half).

Typically females have litters every other year, producing two to four cubs in early spring while the mother is in the den.

Unusual Adaptation: Delayed implantation.
Adult females can hold fertilized eggs for months. The zygote doesn’t attach to the uterine wall unless the female has gained adequate fat by hibernation time. If the female is undernourished, the zygotes will not develop.

Hibernation & Human Health Studies:

During hibernation, bears don’t defecate. Scientists believe that reabsorbing nitrogen-rich urea, helps them to maintain muscle mass while losing between 15 to 30 percent of their body fat. Studies of this phenomena may one day lead to weight loss aids for humans.

Accumulated fat and high cholesterol levels sustain them through the winter. A bile acid that bears generate during hibernations has been found to dissolve gallstones in humans.

Another interesting hibernation fact is that, while in that state, bears repair and regenerate bones. Researchers are studying this with the hope of curing human bone diseases and degenerative arthritis.


Bear cubs are the most vulnerable to predators such as coyotes, bobcats, and mountain lions.

Humans and habitat loss is biggest threat to bears.

In the wild, American Black Bears can live to 30 years. Unfortunately, when a bear is drawn to human activity, their lifespan shrinks to about ten years.

Long range relocation studies have shown that relocation effort are unsuccessful.
Relocated bears will:
– return to the original scene of the disturbance,
– apply learned behavior in new areas, or
– are killed by territorial bears already living in resettlement zones.

Bears & Humans:

Most interactions between bears and humans occur when bears are hungry in spring and late summer/fall.

Once bears become a nuisance to humans, they continue to be a problem.
Problem bears are put down.

The best way to live successfully in high elevation zones, is to discourage bears from establishing bad habits.

Keep a tidy home and be conscious of  items that act as attractant odors.

Guidelines for Bear-Proofing a Home, Property, or Campsite

Use ammonia or bleach to deodorize trash cans.

Put garbage containers in a shed or garage when not out for pick-up.

Freeze smelly food waste and only put it out for collection close to the time it will be picked up.

Use a garbage disposal when possible.

Keep outdoor grills clean and free of meat drippings.

Bring in bird food and pet food at night.

Pick up fallen fruit from around trees.

Install bear-proof compost containers.

Use bear-proof garbage boxes.

Keep food and other fragrant items out of your car.

Close and secure ground level doors and windows at night.

Survey your property for potential hibernation sites; under decks or buildings. Block those places so animals can not access them.



California Department of
Fish & Game Offices
Northern California-North Coast Region
(530) 225-2300

California Department of Fish and Wildlife – Black Bear Biology

California Department of Fish and Wildlife – Black Bear Keep Me Wild Campaign

California Department of Fish and Wildlife – Black Bear Population

California Department of Fish and Wildlife – Statewide Black Bear Policy

California Department of Fish and Wildlife –Living with California Black Bears PDF

KNCO – 6/2015 – Bears On the Move in Nevada County

KVIE Nature – Black Bear Fact Sheet

North American Bear Center

Untamed Science – American Black Bear


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One thought on “American Black Bear – URSUS AMERICANUS

  1. I appreciate all of this great info in one nicely laid out post. The part about bears’ natural processes being studied for potential medical interventions for humans is particularly interesting. It’s fascinating how nature has answers to so many of our human problems.


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