Brown Bear Facts | Alaska Wildlife Guide
While the brown bear closely resembles the black bear, Ursus americanus, there are some major differences. The body size of a brown bear is bulkier and has a prominent shoulder hump, smaller ears, and larger, straighter claws. The brown bear adapted longer claws and larger hump for feeding purposes. Claws help brown bears dig for roots and unearth animal burrows. The muscular shoulder hump helps them dig and attain short bursts of speed for catching loping caribou and moose.
Brown and black bears’ fur can be a variety of shades, making color an unreliable identifier for differentiating between species. A black bear’s fur ranges from dark brown to cinnamon-tinged red to blueish grey and white. Brown bears occur in hues of brown and blond.
Brown bears, along with polar bears, are the largest of the bear species. Brown bear size, however, varies with different populations according to the available food supply. Identifying the weights of certain populations is challenging because heaviness varies widely depending on the season. Bears can double their weight during fall when they are foraging and preparing for winter hibernation, compared to being leaner in the spring. An adult male typically weighs between 300 to 900 pounds, and females weigh between 205 and 455 pounds.
Brown bears from Alaska and the Kamchatka Peninsula are about one-third larger than their inland cousins of Europe, North America and the sub-Arctic, likely due to their abundant food supply of protein-heavy salmon and rich berries. British Columbia, the Alaskan and Katmai coasts, and their adjacent islands such as Kodiak and Admiralty, are home to the largest brown bears. Here, mature males can attain an enormous size, weighing up to 1,700 pounds, with their female counterparts weighing up to 700 pounds. An extremely large brown bear may have a skull 18 inches long and 12 inches wide. Such a bear, when standing on its hind feet, is about 9 feet tall.
Brown bears possess an amazing sense of smell. They are likely able to detect scents from miles away, especially downwind. Their ability to hear and see is about the same as humans. Bears will stand erect on their hind paws in order to gain a better view of the land and to better catch scents on the wind. Brown bears are opportunistic hunters. They and are immensely clever and resourceful, which allows them to adapt to a number of habitats.
Habitat & DistributionBrown bears live in a broad range of ecosystems, including subalpine mountain regions, the icy tundra
Grizzly bears live throughout Alaska, with the exception of the islands of the Bering Sea, the islands south of Frederick Sound and the islands west of Unimak in the Aleutians East Borough. Brown bears are an integral part of
Home RangesBrown bears establish home ranges, which are not technically considered territories because grizzlies will not guard boundaries from one another. The exception comes when a bear feels his exclusive access to a limited resource, such as a rich berry bush, carrion or a kill is worth the risk of vehemently defending. For the most part, however, guarding such an expansive range is impossible, as these bears journey across great stretches of land to find nutrient-rich foods, traveling to different food sites as the seasons change.
The annual home ranges of bears vary greatly in form and size, depending on topography and the food sources contained within them. As adult males range widely during the mating season in search of sows in estrus, their home ranges are substantially larger than those of females. On the Kodiak Archipelago, for the island group separated from the Alaska Peninsula by 20 miles of rough ocean, home ranges encompass 51 to 85 square miles for fully grown boars, and 10 to 36 square miles for adult females.
Family Ties & HierarchyBecause bears are solitary animals by nature, their social system is relatively simple in structure. Sows with cubs form family units that exist for two to three years. All other ties between individual bears are relatively loose and prevail for a short time only.
During the breeding season, sexual partners spend a few weeks at most together. After a female bear severs the family knot by displaying intolerance toward her offspring, the siblings frequently feed, sleep and travel together on their own during their first summer and fall. They also often den together, finally separating the following spring. In some cases, the ties between the siblings persist for another full year. However, there is no firm, stable nexus connecting these sub-adults. The juveniles separate from time to time, usually joining up again within a few hours, but occasionally they do not reunite for several days.
Size and aggressiveness determine the position of a bear in a hierarchy. The huge adult males claim the very top of the ranks. On the ladder of hierarchy, they are followed by maternal females, which owe their elevated position in bear society to their tendency to behave aggressively whenever they perceive their cubs are in danger. The very bottom ranks are held by three- to four-year-old, independent sub-adults.
The hierarchy is not always very apparent, even when bears congregate in great numbers in a small area. The more meager the food supply, the more dominant bears display intolerance toward subordinate animals. However, at the peak of the salmon run, when the waters abound with fish, bears of different size are occasionally observed peacefully catching salmon next to each other.
Conflicts over mating privileges or food resources occur mostly between animals of similar size. Even then, the majority of confrontations are restricted to threat displays occasionally backed up by a few powerful blows from strong paws. Serious injuries are the
Bear BehaviorBrown bears typically search for food during morning and evening hours, though they can be active at any time. During the day, they like to dig slight depressions in the ground to rest in. These “day beds” are usually under the cover of dense foliage or geological formations. In the fall, brown bears will journey miles to forage at their favorite berry sites and salmon streams.
Bears are solitary animals, living neither in herds nor packs, thus social contact between individual animals is relatively limited. Because there is no need for communication beyond the very basics, the animals lack a complex body language, and the ability to vocalize is limited to a narrow range of sounds. Thus, the requisite muscles for facial expressions are poorly developed. The ears are small and unsuited to impart a visual signal, and the tail is a short stump and not at all useful for conveying messages.
Consequently, due to these physical limitations, the communication of bears is more straightforward than in many other animals.
Brown bears react upon threat without much ado and are therefore considered unpredictable. However, this is an inaccurate depiction of the species. Bears do give signals, yet often they are misinterpreted or not recognized as such. Frequently, nervous bears yawn, which erroneously is regarded as the reaction of a bored individual. In addition, a bear experiencing extreme stress may be foaming at the mouth, which indicates the animal is walking the thin line that separates flight and fight. Such signals actually indicate that the so-called magic circle of a bear—a personal space of individual diameter—is violated. Any transgression of a bear’s private sphere results either in the withdrawal of the animal or in the forceful removal of the intruder.
Although communication skills are somewhat restricted, bears are still extremely adaptable animals and curious by nature. They inspect their environment at all times, a behavior that plays an important part in the search for food. In fact, during experiments performed in zoos, it was found that bears investigated objects, such as toys, in their enclosures more intensely and for a longer time than did primates. Every individual bear has a character of its own.
Distinct animals react differently to environmental
As surprised or frightened animals sometimes act according to the motto that attack is the best possible mode of defense, one is strongly advised to walk through the wilderness with eyes wide open and ears pricked, talking or singing loudly in places of low visibility to announce their presence. As a rule, bears show little interest in people and do not consider humans as potential prey.
However, we should never forget that we are guests in bear country, and as such, we should show respect for these animals. Ideally, the impact of our presence should not be felt. Bears should be able to pursue their activities undisturbed at all times. The best photographic opportunities arise when the bears are relaxed, totally ignoring us. If we act obtrusively, they will become nervous and wander off.
The Mating GameThe mating season for brown bears extends from May until early July. Although the majority of bears search for a mate within this period of time, some bruins are occasionally observed much later indulging in the game of love.
In bear populations, both genders are represented in about equal numbers. Females tend to teach their offspring survival secrets for several years, which leaves roughly one-third of them available to the overtures of a male. The consequence of this statistical imbalance is a high competition among males for mating privileges, which, in turn, resulted in the course of evolution in adults—dominant males grow to twice the size of females because larger bears have greater success in passing on their genetic material to the next generation.
Although the mating season spans several months, sows are only in estrous for about three weeks, and they will only allow a male to mount during three to four days at the peak of the cycle. As these animals, for the most part, lead a solitary existence and congregate in a small area only at times when food is available in overabundance, they face the problem of finding a potential mate at the right time. Hence bears, dominant boars
To detect a female in heat, males primarily trust their noses—sex hormones are eliminated from the body through urine. With the use of their exceptionally acute sense of smell, males are able to determine the receptiveness of the female by sniffing the soil and grass where she urinated, walked or slept. With their noses close to the ground, they will unwaveringly follow a promising scent for miles.
At first, this strong interest on the part of the male appears to disturb the female. She tries to evade him, as the much larger boar is a potentially dangerous threat. Often, the pair is observed for several days as they cross meadows, amble through
Ovulation in mammals occurs either spontaneously without any external trigger, as in humans, or is induced by the male, as in bears. Spontaneous ovulation harbors the risk that the ovum dies before conception is achieved. The chance that no breeding partner is encountered at the time of ovulation or soon after is small in animals living in herds or family groups. Not so in bears, which, as a rule, spend much of their adult life
Brown bears usually have two or three cubs per litter. Occasionally, a sow may even give birth to four young. The record to date is six cubs. However, such a large family is about as rare as naturally conceived quintuplets in humans. As the cubs are not identical multiple offspring, and as each ovulation produces only one ovum, several
On the Alaska Peninsula, such an uncomplicated, comparatively peaceful courtship and
In confrontations over the right to mate, boars are sometimes injured. Gaping lacerations on their heads, shoulders
Gestation, Birth, & Raising of the CubsAfter mating in early summer, the female’s fertilized egg begins to divide until it is a spherical sac—called a blastocyst—1 to 2 millimeters in diameter. However, implantation of the embryo into the uterus wall does not yet occur. Instead, the development ceases—a phenomenon called delayed implantation or embryonic diapause.
The blastocyst finally implants into the wall of the uterus in November, after the female has entered the den and is in hibernation. If the sow was able to build up large fat deposits over the summer, the development of the embryo proceeds to completion, and in late January or early
Delayed implantation of the blastocyst prevents the bear cubs from being born in fall at the onset of winter. Also, as an added benefit, the female invests little in the embryo unless her nutritional condition is ideal and the expenditure of her bodily reserves is likely to produce results. A mid-winter time of birth is clearly preferable to a fall delivery, although it is still a far cry from ideal. A later date is impossible due to the restrictions imposed by hibernation.
A fasting mammal supports its bodily processes primarily through fatty acids released from stored fat. As hibernation is, in principle, a prolonged fasting period, bears depend on stored fat as energy during winter sleep. The problem arising in this context stems from the fact that mammalian fetuses are unable to use free fatty acids to meet their nutritional requirements. Thus, the pregnant female is only able to sustain the demands of her unborn young through the breakdown of her own body protein.
Ultimately, this would put her life at risk by inevitably reducing her muscle mass. So, the period of gestation is shortened and the cubs are born in a premature stage. They are raised on the rich milk produced by their mother, which contains up to 40 percent fat in some bear species. This is possible as the cubs, in contrast to developing fetuses, are able to utilize free fatty acids to meet their energy demands.
The blind, newborn brown bear cubs are virtually naked, measure 7 to 9 inches in length, and weigh 14 to 18 ounces. Of all higher mammals, bears give birth to the smallest young in comparison to the size of their mother. After having glimpsed the dim light of the den for the first time, the tiny cubs move without the sow’s assistance toward her almost hairless belly, which, when the mother is curled into a fetal position, becomes part of a natural, warm pouch.
A female brown bear has six nipples—four on the chest and two on her lower abdomen. The newborn offspring are able to locate them by migrating toward her body heat. In the ensuing months, the cubs gain about a 1 every two weeks. In mid-May when they emerge with their mother from their winter home, the young weigh 11 to 13 pounds. By the end of their first summer, they have multiplied their weight yet again.
As a rule, the cubs remain with their mother for two and a half years. At the start of their third summer, the sow, often quite suddenly, quits tolerating her cubs around her, chasing them off. As the female is frequently observed soon after in the company of a male, it is assumed that the aggressive behavior on the part of the mother toward her own offspring, which leads to the severance of family ties, is the result of
The sow nurses her cubs for at least two years, although in their first summer the young supplement their diet with grasses, roots, herbs
Sexual Maturity & Life ExpectancyMale brown bears reach sexual maturity at the juvenile age of 7 years, though, in general, the animal is unable to pass on its genetic material to the next generation until several breeding periods later. Its body size far from the adult maximum, such a young boar stands no chance in a confrontation with a fully grown rival. Females mature sexually one or two years earlier, and some sows experience the joys of motherhood at the young age of 5 years. However, these first attempts at raising offspring are rarely blessed with success.
An adult brown bear lives in a world with no natural enemies. The mortality rates among fully grown animals are low, at about 5 percent per year. By contrast, the chances of survival for bears in their first years of life look rather grim. Almost one-third of cubs do not live to see a second summer. Between 10 and 20 percent of the yearlings disappear, and 25 to 30 percent of the sub-adults released into independence by their mother never attain sexual maturity. Most deaths are caused either by another bear or by malnutrition.
The most critical phase for a young
In the wild, bears may live to 30 years of age. The occasional resilient individual walks a few tentative steps into its fourth decade of life. Though, in general, a bear that has seen more than 20 summers is regarded as old. The life expectancy of captive animals is substantially higher due to excellent medical care and a well-balanced diet. A female brown bear kept in a zoo holds the record for the oldest bruin ever lived. She died at the ripe old age of 45.
Biology & Feeding HabitsBears are unusual members of the order Carnivora. Only polar bears do justice to the standard conception of carnivores by predominantly leading the life of a predator, hunting seals
The diet of most brown bears can be more than 80 percent vegetarian. However, coastal brown bears are an exception to this rule. They stuff themselves with salmon during the summer, and plants play a much smaller role in their feeding habits. In the spring, the bears are forced to rely on flowers, grasses, and roots for sustenance, as no other foods are available. In the fall, the bears on most parts of the peninsula feed on blueberries, soapberries or cranberries.
The nourishment of bears defies generalization, as these animals are highly opportunistic in their feeding habits; they utilize every resource available. Bears eat carrion and will dispossess other carnivores of their prey. Despite their huge bulk and ungainly appearance, they are successful hunters. In some areas in interior Alaska, as much as 40 percent of all moose and caribou calves fall victim to brown bears.
The large vegetarian component of the bear’s diet does not seem to agree with our preconceived image of a predator. On the basis of their food preferences, their ancestors would have matched our image of a carnivore much better. Most of the living members of the family Ursidae can be traced back to a small,
In contrast with specialized carnivores, bears have a greater number of molar teeth, which are also enlarged and cusped to mince up grasses and roots. As it is much more difficult to extract energy from plant matter than flesh, the intestines of bears, in relation to body length, are much longer than those of wolves or lions. However, their digestive tract is still short when compared with ruminants such as cows or sheep. Bears also lack the support of the necessary symbiotic microorganisms, and thus they are unable to break down the cellulose in plant cell walls.
Predators always live between the extremes: periods of gluttony alternated with times of hunger. After a meal, days may pass before a new kill is made. Thus, many predators supplement their diet to a minor degree with vegetation, especially fruit. Bears have made this former dietary addition their main course. The success of the omnivorous nourishment shows is revealed in the family Ursidae. They are substantially larger than their ancestors. Under optimal conditions, such as those found on the Alaska Peninsula or in the Kodiak Archipelago, brown bears may weigh nearly 1,700 pounds! Jointly with the polar bear, these gargantuan animals are the largest terrestrial carnivores in the world.
Due to their mass and their diet, bears differ greatly from typical carnivores such as cats and dogs. For instance, bears walk on the soles of their hindfeet—a posture called plantigrade—whereas cats and dogs have digitigrade feet—where only the toes touch the ground. Digitigrade feet enable the animal to run faster by lengthening the stride. Bears, by contrast, are rather mediocre sprinters, despite the fact that they are able to move at speeds of up to 31 miles per hour. For a long-distance chase, they are much too heavy.
Their legs are relatively short but much more mobile than the limbs of typical runners. The mobility and strength of their limbs are of great importance for bears in their search for food, such as digging for roots. In addition, the animals may not be able to escape danger by fleeing; instead, they are quite capable of defending themselves by means of brute force.
HibernationIn late fall, before the bitter cold of winter descends, brown bears enter dens and begin to hibernate. In the northern part of their distribution area, the animals may spend 60 percent of their lives in deep sleep. By contrast, during the mild winters in southern Alaska, some boars do not retreat at all to protected quarters. However, these individuals show no exuberance either. Instead, they are relatively sedentary, making short movements and appearing at times extremely lethargic. During the worst weather, they spend their time sleeping, bedded underneath some trees or in the shelter of bushes.
Shortage of food is the driving force behind the retreat from active life. As the end of the year draws closer, the land provides less and less in terms of high-energy provisions. Eventually, the bears are unable to even remotely replace the calories burned in the search for food. Hence, there is an advantage to be gained from conserving energy by reducing all bodily functions to a minimum and letting metabolism burn on low flame.
Depending on gender, family status and
Along Brooks River, the last bears leave for their winter home in November. The animals move into the surrounding mountains to excavate a den somewhere at higher elevation where temperatures remain below freezing all through the winter. As a rule, the den is quite small and consists of a short tunnel 3 to 6 feet in length and a chamber barely large enough for the bear to twist around inside. Many of these excavation dens collapse in spring when the soil
In order to balance the weight loss over the winter, bears are forced to consume large quantities of high-energy foods in summer and fall to accumulate ample fat deposits. When a bear enters its den, a healthy adult animal is obese to the extreme, with fat reserves constituting more than 50 percent of total body weight. During winter sleep, the body temperature of a brown bear drops 5 to 16 degrees Fahrenheit, and the pulse slows from 50 beats per minute to about 10. The bear’s metabolic rate is cut in half as well. Still, while lost in deep slumber, a bear loses as much as 30 percent of its body weight, a lactating female loses as much as 40 percent.
In comparison with true hibernators such as marmots or ground squirrels, such numbers are astronomically high. The bodily reserves of these rodents burned during the coldest part of the year are reasonably small, as their body temperatures chill to within a few degrees of freezing (or even dip below), and their heart reaches only 1 to 2 percent of its summertime performance. However, the higher metabolic performance during a female bear’s winter sleep is essential, as otherwise, pregnancy could not take place.
Bears do not drink or eat during hibernation. Neither do they defecate or urinate. They recycle metabolic waste products almost completely, rebuilding proteins so that their muscle mass remains constant or shows only a gradual decline, whereas most other mammals show a continuous loss of body protein when fasting. Unlike humans, their bones are kept strong, even in the absence of physical strain. The recycling of waste products also prevents metabolic waste from accumulating and reaching toxic concentrations. These physiological characteristics have made bears a popular subject in medical research, as it is hoped that the results will provide new treatment and medication for diseases such as osteoporosis and kidney failure.
Research & ConservationThe number of brown bears in the wild has plummeted since the turn of the century. As settlers and their livestock journeyed farther west across America, the bears were pushed out of their homelands. Now, grizzlies inhabit less than 2 percent of their former range. Many threats continue to encroach on what is left of the bears’ habitat, including human development in the form of roads, houses, hotels and golf courses, in addition to mining and logging. Brown bear numbers in the continental United States have dropped from 100,000 in the early 1900s to fewer than 1,000. Thankfully, about 30,000 grizzly bears still roam the mountains of Alaska and western Canada.
Alaska has a vital responsibility to this bear, housing 98 percent of America’s grizzly population, and more than 70 percent of the population in North America as a whole. The bears are managed by the Alaska Department of Fish and Game, which utilizes biological studies of bear populations to best support this noble animal. There are several essential responsibilities of bear management in Alaska, including preserving the bears’ ecosystems, keeping hunting to a minimum, and maintaining healthy, viable populations by studying and understanding bears’ needs.
As economic development in Alaska expands, it becomes more essential for people to understand that what is left of the brown bears’ pristine habitat must be preserved in order for them to survive. This will mean abstaining from some development opportunities for the greater good.
Human ConflictKnowledge of the world in which bears live helps us to better understand conflicts that arise between bears and humans, thus allowing us to take steps to prevent them, thereby protecting bears as well as ourselves. There are two major ways in which bears and people come into conflict. The first involves surprise, close-range encounters. If you suddenly encounter a bear at very close range, it is possible that the bear may not know whether you are a person or another bear. If it thinks you are a threat and that it cannot escape, it may believe that it will have to fight for its life in order to survive the encounter.
You should avoid such situations by being alert and making noise that any bear in the area will recognize as indicative of an approaching person. If the bear hears you coming, it will most likely move away to avoid you. If you do encounter a bear, help the bear to recognize that you are a person and not a threat. Back away slowly to give the bear more space. You could also raise your hands in the air and talk calmly (if you can speak) to the bear. Do not turn your back on the bear, and DO NOT RUN! This will only incite the bear to give chase.
Even if a nearby bear does not seem disturbed by your presence, keep in mind that, unlike people, bears are not sociable. Your presence can make it difficult for a bear to concentrate on fishing and may cause the bear to stop fishing and leave sooner than it otherwise would have. If you stay at least 50 yards from bears, you will make it easier for them to remain in that area. This will also help ensure that other people will continue to have opportunities to enjoy watching bears in the future.
The second major type of conflict arises when people allow a bear to obtain their food, thereby teaching it that they are a convenient source of nourishment. It is essential for people to keep their food away from these animals, in order to avoid human-bear conflicts.
After such an experience, the bear is likely to be attracted to people and may approach them aggressively with the hope that, by doing so, it will be rewarded with food. This situation is very dangerous and is likely to result in the eventual destruction of the bear in order to protect people. The only solution is to prevent the situation from developing in the first place. Recognize that a bear will eat any food that it discovers, and do your utmost to ensure that no bear obtains food from you or in any way associated nearby food with you.
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