San Diego Natural History Museum--Your Nature ConnectionSDNHM Field Guide

American Black Bear | Bear Sign
If You Encounter a Bear | Sightings and Status

Ursus americanus
American Black Bear

Ursidae

Ursus is Latin for bear.

Description

The black bear (Ursus americanus) is the only species of bear remaining in the state of California. The common name of the black bear is misleading. Though black bears east of the Mississippi are predominantly black, in the west various shades of black, brown, cinnamon, as well as blond pelage are common. A small patch of white hair called a blaze is often found on the chest.

An adult male (boar) weighs between 250 and 600 pounds. When standing, a male black bear can be more than 6 feet tall. An adult female (sow) weighs between 50 and 400 pounds. An infant and juvenile bear (cub) gains weight rapidly by consuming fat rich milk from its mother.

Black bears possess non-retractable curved claws on each foot that are about one inch long. These claws allow them to be proficient climbers. They often climb to retreat from predators, including humans.

The lifespan of black bears in the wild can be twenty-five years or more (Zeiner 1990). They lead a mostly solitary life except during mating and when a mother has cubs.

Range and Habitat

Range: The black bear can be found from Alaska to northern Mexico (Hall 1981). The well-traveled Interstate 10 was thought to be a barrier to the southern expansion of black bears in California, however bears are now crossing this barrier with great frequency. In recent years there have been many confirmed sightings in the San Jacinto Mountain Range, south of the San Bernardino area. The current southernmost populations of black bears in California are in San Diego County. This population is reproducing well.

Habitat: Black bears throughout their range characteristically use higher elevation mixed hardwood-conifer forest habitat. They are also known to use lower foothill ranges. Bears thrive where a mixture of trees and meadows exist. In San Diego County the most suitable habitats are inland mountainous regions with habitat complexity, overstory, and diversity.

Dens may be in underground cavities within dense vegetation (Zeiner 1990), in hollowed out logs, caves, within cavities of large trees, and underneath tree trunks.

Natural History

Behavior: Black bears are typically crepuscular—active during the early morning and evening— although they can be active during the day or night. In the southern latitudes bears tend to be active year-round while in the northern latitudes they undergo a period of seasonal dormancy in winter.

In Southern California seasonal dormancy is less common than in nothern latitudes. The mild climate allows the bears to be active year round. Females, though, will den when pregnant.

Reproduction: The females bear young beginning at 4 to 5 years of age. Breeding occurs mainly in mid-summer. Lactating females do not come into estrus, so breeding generally occurs every other year. Bears exhibit delayed implantation for four months (Zeiner 1990); true gestation is only eight weeks. Birth usually occurs in late January or early February. Litter size varies between one and six cubs (Zeiner 1990); cubs emerge from their den in the spring.

Diet: Bears are omnivorous; their molars are designed for crushing food rather than cutting as with meat eating carnivores. Their diet is typically determined by seasonal availability of food. Black bears have extremely varied diets that fall into six food categories: grasses, berries/nuts, insects, small mammals, wood fiber, and carrion.

Conservation Status and Future

In California, the black bear is a game mammal. In 1998 it was estimated that between 17,000 and 23,000 bears inhabited California. Data indicates that these numbers are stable to slightly increasing (Black Bear Mangement Plan-July 1998).

In the last four years bears have become more visible in San Diego County, so much so that recent sightings are more numerous than sightings over the last 30 years. The occurence of these bears is due to natural range expansion. However, continued range expansion coupled with large areas of suitable habitat within the county will likely result in an expanded breeding population in the future. Reasons for this range expansion are not fully known.

Black Bear



History of Bears in San Diego County

The fossil record of bears in our county is small. A smaller version of Ursus was found in the San Diego formation that persisted in the Pliocene (<3 million years old).

At the turn of the century San Diego was home to a stable population of Southern California Grizzly (Ursus arctos magister). This "rather common" species of bear was often seen in the upper elevations of San Diego County (Stephens, 1921:51). Unfortunately this species is now extinct due mainly to unregulated hunting.

The black bear is not known to be native to San Diego County. Many vagrants have been reported over the years. Some bears have even been transplanted to the area. A group of servicemen introduced bears to the Cuyamaca Mountains and Campo between 1917-1919 (Abbot 1935)

Bond noted an influx in the mid-1970s that included Camp Pendleton (1975), Lake Henshaw/Palomar Mountain area (1976), and Buckman Springs (1976).

US Forest Service personnel reported two sightings of an individual bear in the mid 1980s. The first was in 1985 in the Agua Tibia Wilderness and the second was in 1987 on the north slope of Palomar Mountain.

Text: Scott Tremor (SDNHM Research Associate) and
Randy Botta (California Department of Fish and Game)
Photo credit: Tony Mercieca

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