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    • CommentAuthorTRMichels
    • CommentTimeMay 21st 2011
     

    Black Bear Biology & Behavior

    By T.R.Michels

    This is an excerpt from my book "Black Bear Addict's Manual", available in the Trinity Mountain Outdoor Products catalog at www.TRMichels.com

    Home Range

    Black bears are not migratory, but males do roam large areas. Most animals, including black bears, live out their lives in what scientists refer to as a "home range" that they use throughout the year. This annual home range may consist of several different areas, used primarily during the spring, summer, fall and winter, because these areas meet the needs of the animals for food and protection from the weather. These areas are referred to as "seasonal home ranges". Characteristically, a home range does not constitute one large area, but rather several small food source areas andrestingareas, connected by travel lanes.

    Open areas are often avoided by black bears, as they prefer wooded cover. Stream and creek beds are often used as travel lanes, because of the thick undergrowth and they provide a barrier-free escape route. This is particularly true in areas were there is heavy human activity. The size of the home range of an individual black bear varies with the concentration of high energy food sources - the more concentratedthe food ssources are (asthey are in the feeders here), the smaller the rang necessary to maintain a bear. Although they spend the majority of their time in this "home range", there are records of radio-collared bears moving nearly 100 miles through the course of a summer, and then returning to their home by the fall.

    In general, females have a home range that is 3 to 10 square miles in size, while males normally have a range from 10 to 40 square miles. The range of an adult bear is composed of an individual territory, part of which constitutes its exclusive domain, while the rest of it ovelaps the home range of other bears (as it does at most of this preserve, especially near the feeders). The home range of a mature male will often overlap the home range of several female bears.

    Perhaps because black bears range widely—traveling when necessary well over 100 miles outside their normal home ranges in search of food—they have evolved an astonishing ability to find their way home. While a graduate student at the University of Minnesota, my good friend and bear expert Dr. Lynn Rogers (of Lily, Hope and Faith fame) reported that one 450-pound male that found itself 119 miles from its den in mid-October walked straight back to its den over nine consecutive nights.

    Reproduction and Family Structure

    Female black bears usually mature at 3 to 5 years of age with some waiting until later for their first mating. They normally mate with several males over the two to three weeks of the breeding season. Females often breed every other year. And, as we have seen here,they may sychronize "non-birthing" years, if there is a shortage of mast crops (hazel nuts, hickory nuts, acorns) or other prefered food sources. This is due to the fact that duringyears when they are not healthy enough to carry the fetus to full term, as result of poor summer and fall forage, they re-sorb the fetus back into their bodies, and therefore, even though they mated during the spring the year before, they will not give birth. Female black bears breed for the first time at 3½ to 5½ years of age. Mating usually takes place in June and July.

    Males compete for the right to breed, and breeding fights between males may be intense. Older males frequently have extensive scars on their heads and necks from fights in previous breeding seasons. Our male bear "Scar" has a long, jagged, white scar on his snout.  

    Following a gestation period of about seven months, females normally give birth to one or two cubs in the winter den during January or February. Females have one litter every other year. Bears have a reproductive pattern known as delayed implantation. Following fertilization in early summer, a bear’s embryo goes dormant, free-floating in the uterus. After the female dens in late fall, the embryo implants in the uterine wall and development of the fetus proceeds rapidly. Although the total gestation time is approximately seven months, the actual developmental period for the bear fetus is less than three months.

     

    Continued

    • CommentAuthorTRMichels
    • CommentTimeMay 21st 2011
     

    Pregnancy

    During this delayed implantation, the fertilized ovum divides a few times and then floats free within the uterus for about six months with its development arrested. Sometime around the denning period, the embryo will attach itself to the uterine wall and, after a period of eight weeks (January/February), the cubs will be born while the mother is still in the den.

    Delayed implantation serves an important survival need for the female. If she does not have enough fat to carry her through the winter, the embryo will not implant and it is simply reabsorbed by her body. As many as five cubs may be born to an exceptionally healthy, adult, female. Although females with five cubs are rare, the birth of four cubs is not unusual.

    At birth, the cubs are blind, hairless, and very tiny. They weigh from 8 1/2 to 12 ounces. They ar virtually helpless, but they are able to move enough to suckle their mother. In spite of the harsh weather, most cubs manage to stay warm. While the temperature inside maternal bear dens is only slightly warmer than outside, the cubs are more than comfortable clinging to their mother. As the cub's hair grows, insulation becomes less of an issue. About six weeks after birth, the cub's eyes open.

    Within the next five weeks, the cubs will develop rapidly on the rich diet, and they will be able to follow their mother when she leaves the den. They will stay with their mother for the entire first year. They are generally weaned between July and September of their first year, and stay with their mother through the first full winter. Their survival is totally dependent on the skill of the mother in both protecting them and teaching them the basics of what to eat, where and how to get it, where to den, and how to cope with danger.

    As adolescents, the young bears are still in extreme danger. As the sow prepares to breed again, they are driven off. They then become rapidly self sufficient - if they are to stay alive - and they find sufficient food to build up their fat reserves to last over the long winter. Occasionally, young bears will spend a period of time together after their mothers have driven them off.

    At six months, cubs are able to locate food, but generally remain with their mother for over a year—usually denning with her during their second winter. Parental care is solely the responsibility of females; males sometimes kill and eat cubs.

     Adult black bears often weigh from 200 to 500 pounds. Occasionally, large males weighing more than 700 pounds are reported. Black bears stand 27 to 36 inches high at the shoulder and are 4 1/2 to 6 feet long.

     Although black bears come in a range of colors, bears in Michigan are known for their jet-black coat. But, they can be black with brown eyebrows and snout, in the east. On the western side of the Mississippi River and north of Iowa, bears often exhibit other colors; brown, reddish-brown, cinnamon and blond. Bears near Yakutat Alaska are often refered to as Glacier bears, due to their dark or light blue-gray coats. The famous Kermode bears are all white, and can be found in central British Columbia, and the adjacent Islands,includng Kermode Island.

     

     

    An excellent sense of smell and a keen sense of hearing alert the bear to potential food sources and danger. Black bears are somewhat nearsighted, but sight is not an important sense for themr. The bear's sense of smell is its greatest asset. Because 75% of its diet is vegetation, the sense of smell plays an important role. The black bear has the largest ears of any of the four American bears, helping it to hear danger coming from far away and thus enabling it to retreat into the thickets, or leave the area altogether.

     

     

     

     

    Seasonal Activity

    Forage Patterns

    Daily Habits

    Senses

    Size & Color

    • CommentAuthorTRMichels
    • CommentTimeMay 21st 2011
     

    Mortality and Longevity

    Other than humans, black bears have few predators—cougars, bobcats, and coyotes attack cubs if given the opportunity. Male bears may eat cubs. Female black bears have the potential to live into their mid 20s. Male black bears do not typically live as long, rarely attaining 20 years of age.

    Bears are constantly looking for food. Although they are large and powerful, they survive by eating almost anything that is edible and can't get away. Black bears may be seen at any time of the day or night, but are generally most active at dawn and dusk. When traveling from place to place bears move at about 2 to 3 miles per hour. They are lazy, their flat-footed shuffle can be very deceptive. When moving at an all out run, they have been clocked at 35 mph. They can outrun a horse over short distances. They are extremely agile, and is a very capable climber and swimmer.

    Black bears are omnivorous, eating both plants and animals. It has been determined that more than 75% of their diet consists of vegetable matter including greens, berries, flowers, grasses, herbs, roots, and nuts. For the remaining portion of the diet, animal matter such as carrion, fish, insects, and any mammal they can catch is consumed. Black bears are particularly fond of larval grubs, earthworms, and ants found in decaying logs. Bears will take advantage of human foods and garbage, returning to feed on these items regularly if left accessible.

     

     

    In the spring, black bear diets consist mostly of herbaceous plants, from emerging grasses and sedges to horsetail and various flowering plants. In summer, bears typically add ants, bees, grubs, and a host of later emerging plants to their diets. During late summer and fall, bears typically shift their diets toward tree fruits, berries, and nuts, but they still may consume a variety of plants.

    During late summer and early fall, all bears have, as a survival imperative, the need to gain as much weight as possible. Through the harvesting of locally available nut crops, berries, etc., black bears normally make very large weight gains. Such gains may be as much as 30 pounds per week. At such times, foraging may occur around the clock with only short rest periods.

    Fall is a critical season for black bears and they commonly acquire most of their annual fat accumulation at this time. Bears may forage up to 20 hours a day during fall, increasing their body weight by 35 percent in preparation for winter. Typically, a small proportion of the black bear’s annual diet is made up of animal matter, including insects, mice, voles, ground squirrels, fawns and elk calves, eggs, carrion (animal carcasses), and fish, but their availability varies and is often unpredictable. An occasional bear may take livestock.

    Winter Activity

    Although the bear's wintertime slumber is often considered hibernation, it is not. Termed "carnavorean lethargy"or "torpor", the life processes (heart rate, breath rate, body temperature) do not drop as drastically as do those true-hibernators like the woodchuck and ground squirrel. Black bears usually den in excavated cavities under stumps or in knolls or hillsides. Brush piles, hollow logs, or other situations have also been frequently reported.

    While "hibernating", a bear's heart rate drops from between forty to seventy beats per minute to only eight to twelve beats per minute and its metabolism slows down by half. Unlike many other animals that hibernate, its body temperature only undergoes a minor reduction of 5 to 9 degrees.

    During the entire period of "hibernation", the black bear will neither pass urea or solid fecal waste. While urea poisoning causing death would occur in all other animals, bears have developed a unique process of recycling the urea into usable proteins.

     

    • CommentAuthorTRMichels
    • CommentTimeMay 27th 2011
     

     

    Thre is some overlp in informtion here, because It appears my Blak bear Adict's Manual has been lost on my computer, so muuch of this is taken from a previous paper.

    Population & Range

    There are in excess of 500,000 black bears (Ursus americanus) in North America; they are the second largest omnivore or predator in most of Canada and the United States; with only brown bears and polar bears being larger. It is estimated that the population of black bears in the lower 48 states is between 186,000 and 206,000.

    Size

    Black bears may reach lengths of five feet, with exceptional bears reaching eight feet from nose to tail, with shoulder heights from 2-3 feet. Males generally weight from 100-400 pounds, with large males reaching 800 pounds. Females may weigh 90-525 pounds. The weight of individual bears depends on there age, sex, season food and genetics; bears coming out of hibernation weigh much less than they do in the fall. Males generally reach full size by 12 years of age, females are generally full grown by the age of 6. Most black bears loose 50 percent of more of their weight during hibernation, especially females when they are nursing newborn cubs. The heaviest weight recorded for wild lack bears is 902 ponds (for a male) and 520 pounds (for a female). Those weights were measured at peak fall weight however. Most black bears, especially after winter, weigh less than half that much.

    Unusually heavy black bears often have access to supplemental food. Researchers weighed such a bear near Orr, Minnesota (probably near the Vince Shute Bear Refuge) in 1994. Duffy, age 12, weighed 584 pounds on July 13, and 876 pounds on September 5, gaining 8.1 pounds per day during those 36 days. After spending the winter in his den, and after losing more eight during the spring breeding season, he weighed only 465 pounds on July 4, 1995. He had lost 411 pounds (47 percent of his weight) during hibernation and mating. While they may look ponderous on their feet at their fattest in late fall, when they may go through a sleep walking phase prior to denning, they can sprint up to 30 miles per hour, and they can climb trees easily. Under ideal conditions black bears may live 5-30 years. Between 1930 and 2010 there were fewer than 35 known black bear attacks on human beings.

    I hope that provides you with some informational reading, if not usefull and interesting. 

    God bless,

    T.R.