All About Bears

Physical Appearance

Compared to other bear species, the black bear is considered medium-size; males range from 200-500 lbs. and females l50-300 lbs. They come in a variety of colors ranging from black, brown, cinnamon, red and blond. Patches of white are sometimes found on their chests. They may have a tan or black muzzle. Black bears measure about 3 feet high when on all 4’s or about 5 feet tall when standing upright.

Black bears have strong muscular necks, and a heavy body supported by short powerful legs. The highest point of a black bear is the middle of the back. There is no prominent shoulder hump as there is on a grizzly bear. You can recognize a young bear from an older bear by the appearance of the large ears in comparison with its smaller head.

Habitat

Black bears have long been viewed as forest-dwelling animals. However, an unbroken expanse of forest doesn’t provide enough food for black bears. They need berry patches and stream bottoms to satisfy their appetite for plants and insects. You can find black bears in virtually all forested areas of New Mexico. Females usually maintain a home range of five to seven square miles. Males on an average occupy an area of 25 square miles, although they can extend their territories to as much as 50 square miles if habitat quality deteriorates.
Under ordinary conditions black bears display mutual avoidance of each other rather than territorial aggression. A sub adult female’s territory will overlap her mother’s range. Sub-adult males sometimes disperse over great distances, which help maintain the viability of the gene pool by reducing the incidence of inbreeding. When habitat becomes limited or degraded, sub-adult males may encroach on the territory of sub-adult females and force them into marginal areas near human population. This is precisely what happened in 1989 when 23 bears came into Albuquerque. All were sub-adult females driven from their range during a period of drought.

Hunting And Feeding Habits

Bears are omnivorous, which means they will eat just about anything around. Plants compose the overwhelming majority of their diet. Their diet varies according to seasonal availability of foods. In the spring, the diet consists mostly of young grasses and forbs, young succulent shoots, roots, insects and carrion and cambium, the nutrient-rich part of a tree just under the bark. In summer, young grasses, forbs, dandelions, sweet clovers, a variety of mushrooms, watercress, insects, chokecherry, wild raspberries, wild strawberries and wild plum and apples are primary sources of nourishment.

Like humans, bears cannot convert cellulose into an absorbable form and so the mature plants and grasses of summer cannot be properly digested. Rocks and stumps may be overturned in search of grubs, and yellow jacket nests may be invaded. Another favorite in the Sandias is the calorically high “bear corn” or “squaw root," the yellow-red root that grows abundantly underneath oak trees.

In late August, black bear are trying to fatten up for winter hibernation. During this period, they may actively feed for up to 20 hours a day and may ingest 20,000 calories daily. Acorns makes up the bulk of a bear’s fall diet with additional pinon nuts, juniper berries, kinnikinnick (bearberry), and prickly pear eaten to help store fat for the approaching winter. If necessary, they will feed on small rodents, maggots and anthills. True to popular belief, bears do raid beehives for the honey and the bees. They have been known to raid chicken, rabbit, and hamster coops. Males may kill and eat cubs. Such behavior may not fit our image of Pooh or Smokey, but it does maintain a balance between population and available habitat.

Mating

The black bear is not a threatened or endangered species. However, it is vulnerable to extreme population fluctuations because of its mating habits and reproductive cycle. In New Mexico, breeding doesn’t begin until a sow is almost six years of age, and mating occurs only once every two years. Consequently, BearWatch is concerned that wildlife management policies must take care to protect the population of our black bears.

In New Mexico, black bears breed between mid-May and July. Gestation takes seven to eight months. Delayed implantation of the eggs enables the female to breed in the summer and give birth in the winter. This delayed implantation has been termed “an effective means of birth control”. If it has been a good feeding season and the sow has plenty of fat reserves going into the winter season, then all the fertilized ovum will implant, meaning a large litter (up to 3); if it has been an average feeding season, maybe just one or two ovum will implant, resulting in 1-2 cubs. And if it has been a sparse feeding season, the ovum will not implant at all, so that the female bear can use all her fat reserves to keep herself alive. Therefore, even though a bear mates in June, it could be as late as November before the fertilized eggs are implanted. Cubs will stay with their mother 1-2 years. Therefore the female mates about every 2 years, shortly after “evicting” the cubs.

Signs And Sounds

Black bear tracks are very distinctive--the hind footprint resembles that of a human. All bears have 5 toes, with the front foot short and about 4-5 inches wide. The hind foot is long and narrow, measuring about 7 inches. Claw marks may or may not be visible. The claws are non-retractile, meaning they can be seen at all times. The black bears’ tightly curved claws are ideal for tree climbing and digging for insects, tubers, and making dens. They are also strong swimmers. Like a human, a bear’s feet are made for a browsing lifestyle, rather than one of pursuit. However, while bears may appear awkward and clumsy, they are actually very agile. They can run twice as fast as man (up to 25 M.P.H.) and have been known to outrun a racehorse for a short distance.

Bears use trails just as people do, since it's easier to travel on a trail than through underbrush. Be aware of tracks, droppings and other bear signs. Claw marks on trees, rotten logs ripped apart and hair on tree bark from rubbing will allow you to determine better the presence of bears. It's easy to recognize a black bear’s sizable droppings of plant leaves, partly digested berries, apples, assorted seeds or animal hair.

Adult bears make a variety of sounds. The most common is woofing and jaw-popping. Young bears whimper or bawl. Black bears use the same vocalization and body language toward people that they do toward each other. Knowing these sounds can help people react to any bear they may encounter.

The sound most heard by people is a loud blowing, which means a black bear is nervous or afraid. Campers or hikers hear this when a bear retreats or bluffs. Three types of bluffs are common, and all include sudden, explosive blowing. The most common is blowing with clacking teeth---the defensive display of a scared bear. Another bluff is blowing with a short lunge and slapping the ground or an object---an uneasy black bear’s way of saying, “move back”. A more emphatic version is blowing and bluff-charging. Any of these blustery displays can occur when a black bear feels crowded but is reluctant to leave food or cubs. However, displays usually end with bears turning and retreating, perhaps to repeat the performance. Research has shown that these displays are not normally preludes to attack and aggressive behavior by people [yelling, waving arms, making short rushes, throwing things to scare the bear] is almost certain to put a bluffing bear in retreat.

A less common sound is the resonant voice of a bear. This is used to express intense emotions (fear, pain, and pleasure) including strong threats. Black bears with ready escape routes seldom use this threat toward people.

Of all the senses, it is the sense of smell that is the sharpest and that the bear relies upon the most. In fact, with proper conditions, a bear can smell a human approaching from up to one mile away. While a bear’s sense of sound and sight are not its strongest, these senses still exceed mans capabilities. When a human sees a bear and the bear stands on its two hind feet, it is most probably not trying to see better, but to smell what is going on around it.

Black bears are considered the most intelligent North American mammal after man. They are more curious than a chimpanzee and have very good memories. A bear that has learned that ice chests contain food may curiously approach a car, peek through the window, see an ice chest and break into the car. One account tells of a female black bear learning to use rocks to trigger traps. She would wait in a nearby tree for the traps to be set, coming down when humans had left to trigger the traps and eat the bait. Look at your beloved dog that you find so intelligent and be aware that he would lose paws down in an I.Q. test with a bear.

Shelter

Black bears select a surprisingly small den that has one or more openings. The most important aspect of a den to a black bear is that it is in a protected area. The den is small, so that the bear’s own body heat will warm the space. Den openings are often so narrow that an adult human would find it difficult to squeeze through them. In New Mexico, dens are frequently located under outcroppings of large rocks or under tree roots.

It was believed dens were chosen for their thermal properties, but most dens are nearly as cold as the surrounding countryside. Bears gather leaves, grass, and twigs to make insulating beds on which to curl up, leaving only their well-furred backs and sides exposed to the cold. They sleep alone with the exception of mothers with cubs. Most bears use a different den each year. In bad years, a small percentage of black bears die in dens. Unfortunately, some young underweight bears will die while in torpor in drought years. Since urination and defecation don’t occur during hibernation, odor is not produced. This significantly decreases a mother bear and her cub’s chances of being found by predators which include mountain lions, bobcats, coyotes and other black bears that sometimes prey upon the cubs.

Bears And Winter

For black bears, hibernation is more an adaptation for escaping winter food scarcity than an adaptation for escaping winter cold. Black bears do not officially hibernate but enter a state of "torpor", which is a modified form of hibernation. Torpor in New Mexico normally occurs between mid October through the end of March and sometime later. Pregnant sows enter the dens first, with sow with cubs next, followed by younger bears and the last into the dens are adult males. Males usually appear first in the spring, followed by female’s without cubs and finally female’s with cubs. Bears may move from den to den in winter months so it is possible to see them when they are supposed to be in torpor.

The black bear’s metabolic and digestive processes undergo an amazing transformation during its stay in the den. Rather than excreting, the bear has evolved the capacity to reabsorb its waste products and convert them into useful proteins and other nutrients. To survive long winters without eating, drinking, exercising, or passing wastes, hibernating bears cut their metabolic rates in half. Sleeping heart rates drop from a summer rate between 60 and 90 beats per minute to a hibernating rate between 8 and 40 beats per minute.

Rectal temperature drops only slightly, though, from 99-102 degree F in summer to 88-98 degree F during hibernation. Bears can maintain this high body temperature despite their lower metabolism in winter because they develop highly insulating fur and reduce blood supplies to their limbs. Only the head and torso are maintained at higher temperatures. Maintaining the brain at a high temperature enables bears to maintain brain function for tending newborn cubs and responding to danger. Most parasites of bears are adapted to their host’s hibernation cycle and reduce their demands in winter.

Medical researchers are studying black bear hibernation to learn how bears cope with conditions that are problems for people. These findings are aiding studies of kidney disease, gallstones, obesity, anorexia nervosa and other human health problems. Researchers hope that knowledge of bear hibernation/torpor may someday even aid space travel.