Grizzly Bear

Characteristics

Shoulder as high or higher than rump and colored dark brown to blonde. Fur grizzled or uniformly colored. Profile of muzzle will be concave, as opposed to the black bear that have straight or convex muzzles.

Species Specifics

Spanning 3 continents, it is the most widespread bear on earth. Possibly 3 different subspecies (N American grizzly, Kodiak, Eurasian brown) exist.

Physical Characteristics

Muscular shoulders and large claws allow them to dig up small mammals, insects, and roots better than black bears. They can swim well. Bears are the mammals able to survive for half a year or more without eating, drinking, urinating, or defecating. During hibernation, their body temperature lowers from ~100°F to ~93°F.

Ecology

Habitat

Forest, alpine, tundra, desert

Distribution

Home Range: Grizzlies are larger than black bears and have larger home ranges. A male's average range is 80-800 mi2, and a female's average range is 40-400 mi2.

Diet

Roots, tubers, forbs, grasses, sedges, fruits, pine seeds, insects, fish, rodents, ungulates.Seasonal Diet: Grizzly bear diets vary widely depending on their range and the season. Some are carnivorous, while others survive primarily on plants and eat meat only when opportunities arise. In North America, there are two main types of bear diets: inland and coastal. Inland bears eat roots in early spring and ungulates (like elk) that died or are weak from winter. As it warms, they will eat grasses, sedges, forbs, and tubers and will hunt the newly born of several species (elk, deer, moose, muskox, and caribou). Toward the fall they will eat fruits, seeds, and smaller mammals. Coastal bears eat tubers and sedges in early spring and summer, as well as Pacific razors and soft-shelled clams at low tide at exposed mudflats. Salmon are abundant from July to December, depending on the area. After the salmon run, coastal grizzlies will focus on berries, seeds, tubers and grasses.

Ecological Web

Ecological Role: This species serves many roles in ecosystem structure due to their omnivorous, opportunistic nature. Grizzlies are considered apex (top) predators and keep prey populations at a healthy level. In addition, they act as scavengers and remove diseases from the ecosystem and return nutrients to the soil. Predators: Their only predators are humans.

Activity and Behavior

Activity Pattern

Mainly crepuscular, but often active during the day, especially as the season gets closer to hibernation.

Behavior

There are theories that grizzlies maintain a higher body temperature during hibernation because they cannot hide as well as small creatures can and if they can wake up quickly, they can defend themselves from other predators if necessary. They sometimes cache food, to save for later and can congregate along salmon runs.

Social Behavior

Solitary, though ranges can overlap between the sexes. Males and females come together during estrus, and females care for their offspring for long periods. However, during the salmon run, it is not uncommon to see multiple bears, where they will form a social hierarchy (males are more dominant).

Reproductive Behavior

Mating occurs May-July, but the uterine implantation of blastocycts occurs in November, with birth 6-8 weeks after (during hibernation). The interval between successful litters is generally 2-5 years.

Offspring

Typically 2-3 cubs but can be 1-4. 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).

Conservation

Status

Least Concern by IUCN, CITES Appendix II (except Chinese & Mongolian populations under Appendix I), Endangered Species List in US outside of Alaska

Historical

Our California leaders must have admired the power and intelligence of grizzlies, as the species became a permanent part of the California state flag in 1911. Sadly, this beautiful animal that was so admired was hunted to extinction. No wild grizzly was seen in California after 1924. Grizzly bears once roamed throughout the entire western U.S. south into Mexico including the Great Plains and along rivers in desert habitats. They roamed the hills of San Francisco in large groups! Hunting and habitat loss extirpated them from 98 percent of their original habitat in the U.S. including the Great Plains and all habitats south of Yellowstone National Park and Teton National Parks in Wyoming including Idaho, Washington and our own California.

Current Threats

Our Role

Oakland Zoo sponsors People and Carnivores, a Montana based organization aiming to increase co-existence through education and human behavoir change. Oakland Zoo is working with Zoo Parks Partnership to create a new platform for zoos and parks to work together. Our first partnership will be with Glacier National Park and will include support of their Grizzly Bear Research.