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Hidden World of Black Bears

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1.  Almost part of the family

The black bear story is like the gorilla story.  We thought gorillas were ferocious until close study showed them to be mostly gentle.  "We're learning the same thing about black bears," says Rogers.   Both species have a blustery bluff charge that ends without contact. 

Photo: October 7, 1989.   Minnesota. By Marco Visalberghi

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2.  Two-week-old cub in den with mother

Bears give birth to smaller young, relative to mother size, than does any other placental mammal.  Black bear mothers that weigh 175 to 500 pounds produce cubs that weigh less than a pound each in January.  By the time the families leave their dens in April, the cubs weigh 4 to 10 pounds, which is about the expected birth weight for an animal of bear size.  Cubs gradually open their eyes at 5 to 7 weeks.

Photo: February 20, 1990

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3.  Mother and cub in a den

All three species of North American bears give birth during the winter.  The mothers' metabolic rates are slowed by hibernation, but they wake up and care for the cubs like other mothers do.

Photo: April 5, 1983.  Minnesota

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4.  Sleeping beauties

Two content cubs are asleep in their den after nursing.  Their mother, still lethargic from hibernation, is exploring the spring surroundings after an early snow melt.  Newborn cubs do not hibernate.  Their job is to eat, sleep, and grow.  These two weigh four pounds at nine weeks of age.

Photo: March 21, 1987.   Minnesota

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5.  7-year-old mother with cubs in a den under a fallen tree

Three is the most common litter size in the East-two in the West.  The record is six.  When mothers cannot find enough food, milk is limited, so cub mortality is highest in the largest litters.

Photo: March 19, 1972.  Minnesota 

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6.  Cubs first look at the world

Black bears do not produce cubs until they are 3 to 11 years old, depending upon food supply.   This mother first gave birth at age 7.  Here she is 10 with 3 cubs weighing 4½ to 5½ pounds.  She produced 12 cubs by the time she was shot at 18¾.  Black bears can live 30 years or more.  Life spans in hunted populations average 4 years.

Photo: March 26, 1980. Minnesota. 

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7.  Mother carrying cub from den

With her paw, this mother gently positioned her cub behind her large canine teeth, using those teeth as a loose cradle for the cub.   She carried the cub away from the flooding den, keeping it above the melting snow.

Photo: April 2, 1989.  Minnesota. 

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8.  Warming her cub

The mother stopped to warm the cub she was carrying in her mouth.  She lay on her back, placed the cub on her stomach, and brought her hind legs up around it.  The cub snuggled into the warm fur, then sat up, and looked at mom squinting in the sun. 

Photo: April 2, 1989.   Minnesota. 

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9.  Mother caring for her two-month-old cub near a den

Mothers respond to every cry to keep their cubs warm, dry, clean, and fed. 

Photo: March 22, 1992.   Minnesota. 

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10.  Mom and 11-week-old cubs

By July, these cubs replaced their fuzzy brown fur with coarser black fur, and their blue eyes turned brown.  By fall, their black fur was nearly four inches long, and a dense layer of underfur had grown in.  Thick fur in fall and spring makes all bears look fat.    

Photo: April 12, 1989.   Minnesota.

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11.  Cub on white pine

Mothers make over 90 percent of their beds at the bases of big trees with strong, coarse bark.  If a predator appears, cubs can climb that bark more safely than they can climb smooth or flaky bark.      

Photo: July 1, 1989.   Minnesota. 

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12.  Black bear cub  Age: 4 months  Weight: About 10 pounds

Cub growth and survival depends upon food.  By fall, cubs can weigh as little as 15 pounds or more that 160 pounds.  This flexibility in growth rate, depending upon food, helps black bears adapt to habitat conditions from the arctic tundra of Labrador to the mountains and deserts of northern Mexico.

Photo: Late April 1983. Minnesota. 

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13.  A big leap for a black bear

Black bears have blocky bodies built for strength, carrying fat, and conserving heat in winter.  They lack the agility needed for efficient predation.  By late summer, this bear was too fat to make this leap.     

Photo: May 25, 1996.  Minnesota.

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14.  Startled and concerned

Many people fear that bears will sense they are afraid and attack.  However, most people who see bears close-up ARE afraid-and are not attacked.  Bears look a bit like dogs but are less aggressive.   Across North America, dogs kill 16 times more people than do black, grizzly, and polar bears combined.   

Photo: September 8, 1992.   Minnesota.

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15.  Fleeing

Black bears survive by being ready to flee, often to a tree.  During the Ice Age, they lived among powerful predators like saber-toothed cats, dire wolves, American lions, and giant short-faced bears, none of which could climb trees.  Black bears developed the timid personality of a prey animal, which serves them well today among grizzly bears, wolves, and people.   

Photo: September 1988.  Minnesota.

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16.  Cautious

Bears' soft foot pads and soft coats let them move quietly despite their weight.  They can be very elusive unless they choose to show themselves when lured with food.  Over much of their range, they live among people, often unseen.  

Photo: August 1982.  Michigan.

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17.  More wary of each other than of Rogers

"Sometimes its nice to be ignored," says Rogers.  The bears he studies generally regard him as part of the woodwork as they go about being bears.  They forage, nap, play, mate, nurse, chase intruding bears, sleep through the night, make dens, and even argue--as seen here-while Rogers records the details.      

Photo: September 1988.  Minnesota.  By Donna Rogers.

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18.  Recording data

Dr Lynn Rogers stays with his research subjects for 24 hours at a time, entering code letters into his field computer to record behavior, habitat use, and the number of bites taken of each food.  He moves with them as they forage, and rests with them when they sleep.  His backpack has a sleeping bag but no food that could distract the bears from natural foraging.

Photo: April 14,1990. Minnesota. By Bob Cary. 

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19.  Two-year-old male

When males approach maturity, usually at two or three years of age, they voluntarily leave their mothers' territories and look for mating ranges that have females, food, and not too many adult males.  

Photo: June 1989.  Minnesota.

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20.  Mother and cub climbing birch trees for tent caterpillars

This 146-pound mother ate 25,192 tent caterpillars in 24 hours-about 31 pounds or 7 gallons of them.  Tent caterpillars contain oxalic acid and have irritating hairs.  Few mammals or birds eat them, but black bears make them nearly their entire diet in June in years of outbreaks.         

Photo June 27, 1989.  Minnesota.

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21.  Bear watching canoeists

People are moving into bear country in unprecedented numbers, and black bear numbers have increased to about 750,000 across North America, so more people are seeing more bears.

Photo: August 12, 1989.  Minnesota.

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22.  Climbing white pine to get backpack

In years when nut, acorn, and berry crops fail, black bears are as quick as chipmunks to substitute human food.  They prefer natural food, though, and they return to their wild diet the next year if natural food is available.   

Photo: June 1984.  Minnesota.

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23.  Looking for leftovers

Seeing a bear is a joy or a problem, depending upon the person's attitude.  More and more people are moving into bear country.   The attitudes of these people will dictate the future of the bears that live around them. 

Photo: July 1985.  Minnesota.

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24.  Kelly Rogers pepper-spraying a bear

Pepper spray works as well on bears as it does on dogs.   In hundreds of tests, the bears didn't go away mad, they just went away-without any aggression toward the sprayer.  This bear ran away when 5-year-old Kelly sprayed it.  The next day, the bear seemed calm around Kelly's father but ran up a tree when Kelly appeared.     

Photo: August 1986.  Minnesota.

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25.  Mother and cub moving to a fresh blueberry patch

Black bear females share their territories with their cubs and with independent offspring from past litters.  If a territory is crowded, the mother tries to usurp part of a neighboring territory rather than fighting with her own offspring. 

Photo: August 15, 1989.  Minnesota.

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26.  Wary female

This 5-year-old female trusted Rogers and his assistants to walk and sleep with her for 24 hours at a time.  She ignored their familiar sounds, but she reacted to distant, unidentified sounds.  Here, she hears distant voices and is about to retreat. 

Photo: September 1990.  Minnesota.

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27.  Cooling off

Black bears become overheated in open sun, partly because of their dark fur. When body temperature exceeds 104 degrees, they must cool off. They drink little, though, when berries are abundant enough to supply adequate fluid.

Photo: September 1988. Minnesota.  

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28.  Black bear eating hawthorn berries

Wild fruit, nuts, and acorns are the most important foods for black bears in summer and fall. If those crops fail, cubs starve, females abort their fetuses, and some bears follow their noses to human foods. Photo:

September 1988. Minnesota.  

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29.  Black bears cooling off

Bears cool off by lying in the water, by panting, or by resting in the shade with their sparsely furred undersides against the ground.

Photo: August 1989. Minnesota.  

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30.  Mother and 7-month-old cubs

Black bear mothers stay with their cubs until the cubs are 16 or 17 months old. Then, in late May or June, just before the mothers begin attracting males to mate for their next litter, the mothers separate from their yearlings but allow them to remain in the maternal territory.

Photo: August 1984. Minnesota.  

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31.  Seeking safety

Black bears are adapted for forest life and have short strong claws for climbing. Grizzly bears are adapted for more open country and have longer claws for digging. Unlike cats, these bears do not have sharp claws for holding prey.

Photo: August 30, 1989. Minnesota.  

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32.  Black bear male  Age: 7 ½ years  Weight: 876 pounds

Nearly a record for a wild black bear. The heaviest wild male accurately weighed was 880 pounds. The heaviest wild female was 520 pounds

Photo: September 1988. Minnesota.  

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33.  4½-year-old female on patrol

Black bear females often have territories of 2 to 4 square miles. Males roam 20 to 100 square miles or more to find food and females. Home ranges of males overlap with the ranges of other males and with the territories of females.

Photo: October 18, 1993. North Carolina.  

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34.  Time to call it a year

Hibernation is an adaptation to escape starvation, not cold. The timing of hibernation varies with region and is genetically set to the period when natural food typically becomes unavailable. In the north, black bears enter dens in September or October and will abandon artificial food to hibernate on time. In the south, they enter dens in December or January, and some do not enter dens at all if food is available.

Photo: October 1987. Minnesota.  

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35.  Mother and cubs raking leaves into a den

The family stayed at the den from October 10 to March 31.

Photo: October 12, 1989. Minnesota.