Black Bears

Ursus americanus

by Damian Fagan

Photo of a black bear

When my daughter was a two-year-old, our family went for a hike in the La Sal Mountains outside of Moab, Utah. We encountered a female black bear and her two cubs along the trail. The sow “woofed” and the two cubs bolted up separate trees. About a minute later, after the sow sniffed the air, she “woofed” again and the cubs zipped down the trees like firemen sliding down a fire pole. Then the trio wandered off into the woods. My daughter laughed at their antics, but my wife and I were thinking about how effective evasive tree climbing might be for us.

photo black bear tracks

Most black bear-human interactions end like this one, where the bears disappear into the forest. Sometimes the bears chase the hiker down the trail, and occasionally there is a mauling, but these are rare. Just over 63 deaths in the past 110 years have been attributed to black bears. Your chances of being electrocuted by a toaster are higher than dying at the paws of a black bear. Just don’t use those numbers as a green light to mess with a black bear.

Bears will pop their jaws, flatten their ears, rise up on hind legs, snort, woof, whine, blow, roar, moan, wail, cough, and bellow, depending upon their emotion. Posturing, the orientation of head and body sends a display signal to other black bears about one’s standing in the community. Black bears tend to flee when confronted by humans, but may charge or stand their ground.

Range

The American black bear’s scientific name is Ursus americanus. Ursus is Latin for “bear,” and americanus was the name given to the black-colored bears observed by the first Europeans in the Americas.

photo black bear

An estimated 500,000 black bears roamed North America prior to European settlement. Though they still occur in sizeable numbers, black bears are extinct from certain Midwest states, but they may still be found in much of the continental United States and Canada. The bear’s historical range in Mexico is unknown although black bears may be found in five or six of Mexico’s north-central states. Hunting, forest clearing, and urbanization impacted the range of the black bear, which is mainly a forest animal. They may be seen, however, in the canyons of the Southwest, especially in late summer or early fall.

Winter Time

Bear dens vary by locale and conditions. A cave, fallen trees, brush piles, culverts, the base of tree roots, and spaces under buildings all may house the wintering bear. One tree den, found in Louisiana, was 96 feet above the ground.

Current research points to reduced thyroid gland activity as the primary motivator for black bears to hibernate, but this is still under investigation. Early researchers believed that the onset of hibernation was due to the snow, temperature changes, decreased atmospheric pressure or a decrease in daylight hours. But a skinny bear will continue to forage in the winter, despite the “rule” that it should be hibernating. That bear might not survive the winter burning up its limited fat supply.

Black bears are not true hibernators like chipmunks and ground squirrels, for example. True hibernators lower their heart and breathing rates to about 10 percent of their normal activity. Black bears lower their body temperature about 10 degrees and their breathing and heart rates decrease slightly (although some lower their breathing and heart rates considerably). They are better described as “groggy,” alternating between sleep and periods of “teenager wakefulness.”

Black bears, unlike true hibernators that burn protein reserves, use their fat reserves for energy. Their urea, from the urine, is recycled back into the production of muscle tissue, and a bear may gain muscle mass in winter although it may lose 20 to 40 percent of its weight. Most of this is from the fat reserves gained during the summer and fall. One interesting side note is that humans on a starvation diet have problems with the formation of gallstones. Bears produce an acid in called ursodeoxycholic acid that is stored in their gallbladders. This acid prevents gallstones, enhances digestion and enables the bears to lose fat, not muscle mass, during their winter slumber. Though some black bears are taken illegally for their ursodeoxycholic acid, a black market product, a synthetic form of this acid has been created using cow bile. The product is used to prevent or dissolve gallstones.

During a five-month hibernation, a female bear gives birth to two or three cubs (rarely, up to six). Though the bears mate in mid-summer, the fertilized embryos do not implant on the uterine wall until November. This delayed implantation means that the young will be born in January. The cubs are born with their eyes open and are active after five or six weeks. They nurse on high-fat milk and snuggle up with the sow to stay warm.

When the cubs and sow leave the den in the spring, the cubs weigh four to eight pounds. The young quickly gain weight and may tip the scales between 15 and 165 pounds by mid-summer, depending upon the availability of food. Generally, the cubs will spend the next winter with their mother in a winter den before they disperse the following spring.

photo black bear tracks in petroglyphs

Physical Characteristics

Not all black bears are black. They may be blonde, cinnamon, reddish or chocolate brown. The guard hairs are long and coarse while the underfur is soft and dense for insulation.

A black bear’s head is broad with a long, narrow muzzle. The female’s head is generally more slender and long-pointed than the male’s. Black bears have 42 teeth; their adult teeth are in by age 2 and a half. Their sugary diet may cause tooth decay and loss of teeth, which may lead to poor health or starvation. Like tree ring dating, the tiny rings or “cement deposits” around a premolar tooth can serve as an indication of a bear’s age.

The adult black bear averages two and a half to three feet tall, from paw to shoulder, and four to six feet in length, tail to nose. They lack the distinctive shoulder hump of their cousins, the grizzly bear. Though seemingly large and clumsy, the black bear is extremely dexterous. It can handle small objects.

Males weigh more than females, sometimes up to 33 percent more. The weight range for adult male bears varies by diet and habitat, but an average is about 250 pounds. The general range for adult males is 125 to 600 pounds. The heaviest recorded black bear weighed 902 pounds.

black bear track in sand

Like humans, bears are plantigrades: they walk on the whole sole of the foot. Their flat feet have five toes (Panda bears have six), and their walk is slightly pigeon-toed. Their leathery soles are dark in color and deeply wrinkled. The claws on the hind and fore foot are about the same length and are thick at the base and taper to a sharp point; the foreclaws are sharply curved. Its track may serve as an indicator of age, sex, weight and species. An average adult male bear’s forefoot track measures four and a half inches long by four inches wide. Its hindfoot track measures seven inches long and four inches wide.

Diet

Bears are omnivores and their diets run the menu from grasses to carrion. They eat insects, berries, nuts, roots, grasses, herbs, bees, honey, insects, fish, young deer or elk, road kill, dog food and human food. Like Yogi, a black bear never saw a picnic basket it didn’t like.

Bear Trivia

A grouping of bears is called a “a sloth of bears.” If asked which bear they know the best, school children might say “Yogi,” “Teddy” or “Smokey,” not black bear or grizzly.
If the winter weather turns mild a black bear may emerge from its den and take advantage of a “mid-winter snack.”
Scientists with the International Hibernation Society are studying the genetics behind hibernation and believe that one day, humans involved in space travel or medical treatment for soldiers may be made possible through hibernation.
Black bears can sprint up to 30 miles per hour.
Black bears have a very good long-term memory. This helps them return to favorite berry patches or find their way home if they range far from their territory.
In the wild, black bears can live to be 21 to 33 years old.
Bears are good swimmers and may call on that ability to cross a river or a lake. One black bear reportedly swam nine miles in the Gulf of Mexico.
An adult male bear is called “a boar.”
Hibernating black bears may go 100 days without eating, urinating or defecating.

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