American Black Bear

California Trail

Location

In the Zoo

Scientific Information

Scientific Name: Ursus americanus
Class: Mammalia
Order: Carnivora
Family: Ursidae
Genus: Ursus

Size

Male

Female

Height: 2.3-3.3 feet 2.3-3.3 feet
Length: 4-6.2 feet 3-5 feet
Weight: 130-500 pounds 90-300 pounds
Maturity: 3-4 years. 4-6 years

Lifestyle and Lifespan

Diet: Omnivorous
Activity Timeframe: Diurnal
Interactivity: Solitary
Sexual Dimorphism:
Gestation: 6.5-8.5 months
Lifespan in the Wild: 25 years
Lifespan in Captivity: 35 years

Geographic Range

Most of Canada, 41 US states, and 8 states in northern Mexico.

Conservation

Status in the Wild:
Threats:

Characteristics

Rump higher than shoulder with prominent ears. Usually black with a brown muzzle, however can be colored cinnamon, dark brown, or blonde and in small areas in British Columbia or coastal Alaska, white or blue-gray, respectively. Profile of muzzle will be straight or convex, as opposed to the brown bear that have concave muzzles.

Species Specifics

There are 16 subspecies proposed, 2 in CA. Their closest living relatives are Asiatic black bears (polar and brown bears are close relatives to one another; black bears are separate).

Physical Characteristics

Black bears have smaller claws than brown bears because they are adapted more for climbing than digging. They have the ability to slow their metabolic rate down yearly in the winter for hibernation (though some southern black bears only sleep for a few days). They enter a 'walking' hibernation first when they are alert but do not eat or drink often, then body systems slowly slow down until they stay in their chosen den. Their heart rate is 40-70 bmp during the summer and slows to 8-10 bmp during hibernation. They can be roused easily from hibernation, hypothesized as an adaptation for emergency situations (such as earthquakes). They can also change dens up to 4 times during hibernation and awaken during warm spells.

Ecology

Habitat

Habitat Type: Primarily temperate and boreal forests as well as swamps

Distribution

Home range sizes vary depending on the ecosystem, but the average for females is 4.6-19.3 mi2 and 45.2-77.2 mi2 for males. Mothers have been known to lead cubs on treks of up to 60 miles from their home ranges to show cubs seasonal food (such as special berry patches or a salmon run).

Diet

Generalist, opportunist omnivore. Vegetation, roots, buds, fruits, nuts, insects, vertebrates (from fish to mammals) including carrion. Seasonal Diet: In early spring, their diet includes herbs, buds, young leaves, occasionally carrion, or nuts left over from the previous fall. Later, they add insects and young deer and moose. By summer, berries and nuts are their main food source (they can eat tens of thousands of nuts or berries each day). In certain areas, especially where grizzlies are absent, they eat a lot of fish. Also consume human food or trash at any point. They eat 11-18 lbs. of food per day and can double their weight prior to hibernation.

Ecological Web

This species is very important to ecosystem structure due to their omnivorous, opportunistic nature. They act as scavengers removing diseases from the ecosystem, as predators, as prey on occasion, and they play an important role in returning nutrients to soil. All of these roles combined help to increase species diversity where they are found. Predators: Adult bears are considered apex predators but wolves and brown bears have been noted killing them. Cubs are frequently are killed by wolves, brown bears, coyotes, bobcats, lynx, and mountain lions and 1.5-year-old males are often killed by wolves, mountain lions, and hunters.

Activity and Behavior

Activity Pattern

Typically diurnal, but can be crepuscular. This is possibly to escape midday heat in warm environments and/or by human activity. Can also be seen active during the night. In the summer, because they need to increase weight for the winter, they need to spend almost 20 hours a day eating, an average of one berry per second.

Behavior

Have an unaggressive nature, which has led to more human tolerance. With this, they have been able to obtain more human-related food, which is easier for them to find and generally has a higher calorie count. Now they can mature faster and produce more offspring, which has lead to an increase in their overall population. Mothers eat their cubs' feces in the den to keep the den clean and so the smell is not an attractant for predators. They communicate territories via scent-marking (with urine and feet) and rubbing, clawing, or biting tree trunks.

Social Behavior

Solitary, though males' ranges generally overlap with several females. Come together during estrus, and females take care of cubs for long periods.

Reproductive Behavior

Mating usually occurs in May-July, but the uterine implantation of blastocysts occurs in November, with birth in January (during hibernation, so the female partially wakes). Females in estrus will travel throughout their territories more often to increase chances of finding a mate, and males' ranges generally overlap the range of several females. During the middle of her estrus period (3-5 days) she will allow copulation; which is generally 30 minutes but can be up to an hour. For these few days, the male and female will feed and sleep together, and copulate frequently. Infanticide can occur; males kill females' cubs to copulate with her to ensure his genetic survival.

Offspring

2-3 cubs are most common, but 5-6 occur as well. Cubs generally stay with their mother for ~17 months. If females have only 1, they can abandon it (a female that stays with 1 cub for over 1 year ends would have fewer total young overall than if she abandoned the single cub and produced 3 the following year). Generally, they have offspring every 2 years.

Conservation

Status

Least Concern by IUCN, CITES Appendix II. In CA, considered game mammal. Population Trend: Increasing

Historical

Though its range extends from Canada through Mexico, it has been extirpated from large parts of its former range, especially in the Midwest and Mexico. Today, they inhabit 60% of their previous range.

Current Threats

Our Role

Exhibit and Educate

How You Can Help

Do not hunt bears and contact your government to express your interest in black bear conservation and decreasing fragmentation between populations. Properly store your food and pick up trash when you go into bear territory. Drive safely and slowly to prevent road kills. Never come between a mother and her cubs. Depredation occurs with bears when they are too habituated to humans or if humans attack them. (From 1900-2000 there were 52 confirmed cases of humans killed by American black bears.) If we clean up after ourselves and pay attention to our surroundings, we can easily save the lives of bears. If you witness an illegal poaching, call 888-DFG-CALTIP (Californians Turn In Poachers and Polluters), or donate to the CalTIP Foundation for reporter rewards.

Fascinating Facts

This is the only bear whose numbers are increasing virtually throughout its range.

The period of time before hibernation when black bears gorge themselves and 'binge' is called hyperphagia, and is thought to be triggered by the amount/angle of sunlight the bear experiences. This photoperiodism is also the mechanism that causes deer to grow antlers in the spring and go into rut.

During hibernation, though their heartbeat slows, their body temperature only falls 5-7°F.

Due to their special fasting metabolism, their bodies only burn fat, not carbohydrates or proteins. Burning fat produces by-products (such as water) that bears can reabsorb and continue to use, which means during their 5-8 month sleep, they do not urinate or defecate at all.

References

Convention on International Trade in Endangered Species of Wild Fauna and Flora Appendices I, II, and III. (2012). Retrieved April 12, 2012 from http://www.cites.org/eng/app/appendices.php

Taylor, Dave. Black Bears: A Natural History. 2006

Garshelis, D.L., Crider, D. & van Manen, F. (IUCN SSC Bear Specialist Group) 2008. Ursus americanus. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.1. . Downloaded on 26 August 2012.

Elbroch, M & Rinehart, K. Peterson Reference Guides: Behavior of North American Mammals. 2011.

MacDonald, David. The Princeton Encyclopedia of Mammals. 2009.

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9777 Golf Links Road Oakland, CA 94605