California Black Bear (Ursus americanus californicus)
California Black Bear (Ursus americanus californicus)
General Distribution
Black bears are not native to southern California. Their absence from this region is believed to have
been a result of competitive exclusion by California grizzly bear (Ursus arctos californicus). California
grizzly bear was extirpated in California near the turn of the century, and black bears began appearing in
Ventura and Santa Barbara Counties (Grinnell and others 1937). In the early 1930s, the California
Department of Fish and Game initiated a translocation (introduction into the San Gabriel and San
Bernardino Mountains) of 28 black bears into southern California to supplement the natural range
expansion (Stephenson and Calcarone 1999).
Current black bear populations are known from Ventura and Santa Barbara Counties on the Los Padres
National forest; the San Gabriel Mountains on the Angeles National Forest; and the San Bernardino and
San Jacinto Mountains on the San Bernardino National Forest. Several sightings have more recently
been reported from Palomar Mountain, Buckman Springs, and the Agua Tibia Wilderness Area on the
Cleveland National Forest (Tremor and Botta 2000). Systematics
Of the 16 subspecies of black bear (Ursus americanus) recognized by Hall (1981), northwestern black
bear (U. a. altifrontalis) and California black bear occur in California. These two subspecies are
separated geographically by the crest of the Klamath Mountains (California Department of Fish and
Game 1998). California black bear is the only subspecies that occurs on the four southern California
national forests. Habitat Requirements
Black bear occupies a variety of habitats, but populations are densest in montane hardwood, montane
chaparral, and mixed-conifer forests with a wide variety of seral stages (California Department of Fish
and Game 1998). Vegetative and structurally diverse habitats are important to black bears because they
provide a variety of food types. Black bears may also seasonally inhabit annual grasslands and valley
foothill hardwood habitats (California Department of Fish and Game 1998). In the southern California
mountains, black bears will follow riparian corridors down into low-elevation habitats (Stephenson and
Calcarone 1999). Recently burned or logged forest can provide high-density fruit and berry production,
whereas unmanaged and mature hardwood forests provide a variety of nuts and acorns (Lariviere 2001).
Female black bears require secure, dry den sites for bearing and rearing young. Dens are also used by
both sexes during periods of seasonal dormancy in the winter. Den sites have been found in hollowed-out
trees, slash piles, root excavations, under large rocks, and occasionally on open ground (California
Department of Fish and Game 1998, Lariviere 2001). Reproduction
Female black bears reach sexual maturity generally between 3 and 5 years of age (Pelton 1982). Black
bears breed in June and July and young are born during January or early February. Litter size ranges
from one to four cubs and is probably influenced by the physical condition of the mother in early winter
(Lariviere 2001). Although black bears are capable of breeding yearly, the frequency of breeding varies
from 1 to 4 years (Lariviere 2001) and is strongly correlated with food availability (California
Department of Fish and Game 1998). Daily/Seasonal Activity
Black bears can be active during the day or night. They are typically crepuscular, concentrating most of
their activity during the early morning and evening (Tremor and Botta 2000). In areas inhabited by
humans, black bears become predominantly nocturnal and secretive (Lariviere 2001).
Black bears in southern latitudes are active year-round, whereas bears in northern latitudes tend to
undergo a period of seasonal dormancy in the winter (Tremor and Botta 2000). Because southern
California generally has a mild climate, seasonal dormancy is less common and black bears are usually
active year-round. However, pregnant females are less active and often den in the winter (Tremor and
Botta 2000). Diet and Foraging
Black bears are omnivores and consume a variety of plant and animal material including grasses, berries,
nuts, acorns, wood fiber, insects, reptiles, birds, small mammals, and carrion (Tremor and Botta 2000).
Seasonal variations exist in the type of foods eaten by black bears. In the spring, black bears consume
mostly new vegetative growth and animal carcasses. During summer, their diet consists primarily of
herbaceous material and fruits. During autumn, berries and mast (acorns and nuts) comprise the bulk of
their diet (Lariviere 2001).
The diet of urban California black bears in the San Gabriel Mountains was analyzed by examining bear
scat collected from urban areas (Van Stralen 1998). Based on the total content of all scat analyzed,
about 57 percent was native plant material (hollyleaf cherry, manzanita, redberry, grasses, and coast live
oak); 26 percent was nonnative plant material (figs, peaches, apples, apricots, avocados, and domestic
cherries); 14 percent was human garbage (paper, plastic, and metal); and 3 percent was animal matter
(fly pupae and bird bones). Territoriality/Home Range
The home ranges of black bears vary considerably and are determined by sex, age, season, and
population density. The size of a home range is also largely dependent on food availability;
concentrations of certain food resources can result in temporary range expansions (Pelton 1982). Black
bears in northwestern Montana have been known to travel more than 100 miles (160 kilometers) to take
advantage of available food supplies (Rogers 1987). Past studies have shown that the home range size
of adult males is often 3-8 times larger than the home ranges of adult females. Using radio-telemetry,
Van Stralen (1998) determined (with 95 percent confidence) the home range size of three urban males to
be 2.9-11.0 square miles (7.4 to 28.4 square kilometers). The single female in this study had a home
range of 2.1 square miles (5.4 square kilometers). Previous studies in southern California have reported
home range sizes of 3.3, 7.5, and 9.7 square miles (8.6, 19.5, and 25 square kilometers) (Van Stralen
1998).
Adult female black bears in northwestern Montana established territories in the summer (Rogers
1987). During other times of the year, black bears establish temporal spacing between each other and
maintain these areas through a dominance hierarchy system (Pelton 1982). Predator-Prey Relations
Black bears have very few natural predators. Bobcats, coyotes, or other black bears may occasionally
kill young bears (Lariviere 2001). Most black bear mortality is human induced, predominantly by
hunting. Bear mortality occurs when problem bears are removed from the population to protect property
or for public safety. Vehicles also kill a number of bears annually. Literature Cited
Bean, R.A. 2001. California's black bear population is healthy and growing. California Game & Fish
Magazine.
Big Game Hunt. 2002. Expanded elk and black bear hunting proposed -
Expanded_Elk_and_Black_Bear_Hunting_Proposed_03080212.html [Homepage of California
Department of Game and Fish], [Online]. Available: http://www.biggamehunt.net/sections/California/
California Department of Fish and Game. 1998. Black bear management plan. Sacramento, CA.
Grinnell, J.; Dixon, J.; Lindsdale, J. 1937. Furbearing mammals of California, their natural history,
systematic status, and relations to man. Volume 2. Berkeley, CA: University of California Press.
Hall, E.R. 1981. The mammals of North America. 2d ed. New York: John Wiley & Sons.
Lariviere, S. 2001. Ursus americanus. Mammalian Species 200: 1-7. Published by the American Society
of Mammalogists.
Pelton, M.R. 1982. Black bear Ursus americanus. In: Chapman; J.A.; Feldhamer, G.A., eds. Wild
mammals of North America: Biology, management, and economics. Baltimore, MD: The Johns Hopkins
University Press; 504-514.
Rogers, L.L. 1987. Effects of food supply and kinship on social behavior, movements, and population
dynamics of black bears in northeastern Minnesota. Wildlife Monograph 97.
Stephenson, J.R.; Calcarone, G.M. 1999. Southern California mountains and foothills assessment:
Habitat and species conservation issues. General Technical Report GTR-PSW-172. Albany, CA: Pacific
Southwest Research Station, Forest Service, U.S. Department of Agriculture.
Tremor, S.; Botta, R. (Eds.). 2000. Ursus americanus American black bear. San Diego Natural History
Museum field guide [Homepage of the San Diego Natural History Museum], [Online]. Available: http://
www.sdnhm.org/fieldguide/mammals/ursu-ame.html.
Van Stralen, G.E. 1998. Home range size and habitat use of urban black bears in southern
California. Northridge: California State University. Master's thesis.
Information gathered from California DFG - California Interagency Wildlife Task Group
