Ursus americanus
American Black Bear
By Sayer Larson
Description:
Black bears are the third largest mammal in Wisconsin, with elk (Cervus elaphus)
and moose (Alces alces) the only larger mammals. They are the commonest, most widely
distributed and smallest of the bear family Ursidae.
Black bear coats are usually black in color, but can range from black to dark
brown. A tan muzzle is prevalent, and about 25 percent of bears have a whitish, V-shaped
throat patch (Kurta 1995).
Black coat
Insert pic of bear w/ black coat
Dark brown coat
Insert pic of bear w/ brown coat
Adult male’s average 1,200-1800 mm (47-70 in) long and weigh between 110160 kg (250-350 lb). Adult females, although smaller, average 1250-1500 mm (50-58 in)
long and weigh between 55-81 kg (120-180 lb). Adults average 610-920 mm (24-36 in)
at the shoulders. A recorded weight of 315 kg (700 lb) occurred in a Wisconsin black
bear (WDNR 2003c).
The eyes are small relative to the head, and the ears are short, rounded and erect.
Each foot has five toes, each equipped with a non-retractable claw. The tail, which is
almost concealed in their fur, ranges in length from 80-125 mm (3-5in) (Kurta 1995).
The black bear can be easily distinguished from the brown bear (Ursus Arctos).
The black bear does not have a muscular hump behind shoulders, less concave muzzle,
rounded forehead, and is much smaller (Burt 1980). Also, the claws of a black bear are
much shorter and curved, there is little to no gap between the footprint and claws
(Northwest Territories 2001).
There are 16 recognized subspecies of black bears; the Wisconsin subspecies is
Ursus americanus americanus (Synder 1991).
Distribution in Wisconsin:
- Current Distribution
The 2003 Wisconsin black bear population is estimated at 11,150 (WDNR 2003a).
The following map was obtained from the WDNR, and shows the current distribution of
black bears in Wisconsin. The map illustrates primary, secondary, occasional and rare
ranges of the bear. They are most common in the northern third of Wisconsin, with about
one bear per 10.4 square kilometers (4 square miles).
Figure from WDNR (2003b): http://www.dnr.state.wi.us/org/land/wildlife/hunt/bear/popndist.htm
- Historical Distribution
Historically, before European settlement, black bears inhabited most of the
forested regions of North America, including the entire state of Wisconsin (Hall 1981).
Before 1985, uncontrolled limits and increasing harvests caused the bear population to
decline. After a closed season in 1985, a new system of bear hunting and harvest control
was enacted in the 1986 season. Since then, the bear population in Wisconsin has
increased steadily to a healthy population (WDNR 2003b).
Ontogeny and Reproduction:
- Bear life cycle
Born in a winter den, at birth a healthy cub weighs between 7-12 ounces. Cubs are
born relatively helpless, as noeonates, the eyes do not opening for 25-30 days and they
are lightly furred. Along with being blind and cold at birth, the mother is usually asleep,
but they instinctively make their way to the mothers milk supply. Emerging from the den
in spring with their mother, they will begin to eat solid foods in about two weeks.
Although a cub is weaned in September of their first year, they will remain with
their mother and share the wintering den. In the following spring, they will disperse or
the mother will chase them off to stop inbreeding from occurring. If the cub survives the
year, it has an excellent chance of living a long life.
Black bears reach sexual maturity at 3.5 years old. Females are ready to mate at
this age, but males tend to mate at 4-5 years old. Females may not successfully raise a
litter of cubs until the age of six or more (Weber 1994). Breeding occurs in June to midJuly. Boars (male bears) are drawn to the scent of a breeding female about a week before
she comes into heat, giving the pair time to get acquainted with each others presence.
They exhibit delayed implantation, meaning that the embryo does not implant in
the uterine wall of the sow until winter dormancy begins. If a female is sickly or unable
to put on enough fat needed for denning, the pregnancy is spontaneously aborted.
A female black bear will normally give birth to 2, but occasion 1 or 3, with a
reported maximum of 6 cubs. Gestation is relative, at about 7-7.5 months (Burt 1990).
Bears have an average life span of 10 years in the wild; can reach up to 30 years.
They reach maturity at age 5-7, but can happen at age 3. Premature death of adult bears is
usually human related, in young; it is from malnutrition (Kurta 1995).
- Predators:
The short list of black bear predators consists of humans, grizzly bears (U. arctos),
and other black bears. Coyotes (Canis latrans) may prey upon cubs (Snyder 1991).
Ecology and Behavior:
- Nutrition
Although black bears are in the order carnivore (carnivores), they are an omnivore.
Even though they possess large canines, the carnassial pair is poorly developed and takes
a more bunodont shape, for grinding and crushing fruits and insects. Only about onequarter of their diet is of animal food (Kurta 1995).
Plants and insects are the most important food items in a bears diet (Payne 1998).
Kinds of fruit eaten include raspberries, blueberries, strawberries, blackberries,
cranberries, strawberries, apples and cherries. They rip open rotting logs, overturn rocks
and dig in the ground searching for invertebrates. And occasionally eats fish, rabbits,
mice, and, rarely a deer fawn.
- Behavior
Black bears are primarily nocturnal (crepuscular), and occasionally seen during
any part of the daytime. They are solitary creatures, but frequently over lap home ranges
of neighboring bears. Although female bears with cubs will go out of the way to avoid
male bears, because a mature male will sometimes kill the cubs of a female to bring her
into estrus.
- Ecology
The dormancy for which they go into was coined “carnivorean lethargy.” The
heart rate declines from 40 beats/minute to 10 beats/minute, and body temperature falls
from the normal 38oC (100oF) to 33oC (91oF) during lethargy (Kurta 1995). Bears need to
gain about 50-60 pounds of fat to sustain them through this dormancy. This lasts from 4-7
months, and can be longer in colder climates.
Black bears prefer forested and shrubby areas but will inhabit wet meadows,
riparian areas, burned areas, ridge tops and swampy hardwood and conifer forests. In the
spring they seek southerly slopes in lower elevations for forage, then gradually transition
to higher elevations on northerly and easterly slopes as the summer progresses. They use
dense cover for hiding, thermal protection, and bedding. They climb trees to escape from
danger (Snyder 1991).
Home range for an adult male differs greatly then that of an adult female. The
home range for an adult male averages 20,000 to 35,000 acres. An adult female’s home
range is considerably less, averaging 4,200 to 7,800 acres (Koehler 2003).
Economic importance:
- Positive
Black bears in Wisconsin are treated as game animals with regulated hunting. In
2002, 2,437 black bears were harvested in Wisconsin (WDNR 2003b). They are hunted
for meat, cloths, rugs and trophies.
- Negative
Some black bears take the easy way out in obtaining food, and therefore are
termed “nuisance bears.” These bears will raid garbage cans, campsites and the town
dump looking for an easy meal. Although they are usually harmless, these bears may be
ill of injured and should be avoided. Some bears become such “nuisance bears” that they
must be relocated or exterminated.
Remarks:
Quick facts
- Bears can run up to 30mph for short distances.
- They are also great climbers and swimmers.
- Neartic, which means they are located in the region of plant and animal life in the Arctic and
temperate areas North America
Literature Cited:
WDNR 2003a. 2003. 2003 Black Bear Forecast. Available (December, 2003)
http://www.dnr.state.wi.us/org/land/wildlife/hunt/seasforc/bear.htm
WDNR 2003b. 2003. Black Bear Population and Distribution. Available (December,
2003) http://www.dnr.state.wi.us/org/land/wildlife/hunt/bear/popndist.htm
WDNR 2003c. 2003. The Black Bear. Available (December, 2003)
http://www.dnr.state.wi.us/org/caer/ce/eek/critter/mammal/bears.htm
Burt, W. H., R. P. Grossenheider. 1980. Third edition. Peterson Field Guides: Mammals.
Houghton Mifflin Co., Boston, New York
Hall, E.R. 1981. The mammals of North America. 2nd ed. John Wiley and Sons, New
York. 1,181 pp.
Koehler, G. M., and D. J. Pierce. 2003. Black bear home-range sizes in Washington:
Climatic, Vegetative, and Social Influences. Journal of Mammalogy 84:81-91.
Kurta, A. 1995. Mammals of the Great Lakes Region.University of Michigan Press,
U.S.A.
Northwest Territories: Resources, Wildlife, and Economic Development Division. 2001.
"Encountering Bears." Available (December, 2003)
http://www.nwtwildlife.rwed.gov.nt.ca/Publications/safetyinbearcountry/encounters.htm .
Payne, N., B. Kohn, N. Norton, and G. Bertagnoli. 1998. Black bear food items in
northern Wisconsin. Transactions of the Wisconsin Academy of Sciences, Arts, and
Letters. 88:263-280.
Snyder, S. A. 1991. Ursus americanus.
http://www.fs.fed.us/database/feis/animals/mammal/uram/index.html
Weber, K. T. 1994. Analysis of black bear habitat in northern Wisconsin. Transactions of
the Wisconsin Academy of Sciences, Arts, and Letters. 82:
Reference written by Sayer Larson, Biol 378: Edited by Chris Yahnke. Page last updated