Mark Betram/U.S. Fish and Wildlife

Black bear cubs weigh only a half-pound on average when born.

Basic Biology

• Color: Most are not black but brown or even blond or reddish brown
• Weight: Average adult male is 300 to 350 pounds and female is 200 to 250 pounds
• Diet: Mostly grasses and berries with acorns as a favorite food
• Hibernation:  Reduce body temperature, pulse rate, and respiration to conserve energy
• Reproduction: Females give birth while in a half-sleep hibernation mode to a litter of one to three cubs
• Young: Cubs remain with their mother until about 16 to 17 months of age

U.S. Forest Service

American black bears are suited to Yosemite's forest habitat.

American black bears (Ursus americanus) in Yosemite National Park have long been of intense interest to park visitors and managers. Seeing one of the approximately 300 to 500 black bears in Yosemite can evoke excitement, awe, and fear. Visitors who spot a bear sauntering across a meadow or eating berries in a wetland should consider themselves lucky.

But, if the brown bear, also known as the grizzly, is on California state flag, why not look for it when in Yosemite? This is because, in California, there are no more grizzlies. When Euro-Americans arrived, they found a large population of grizzlies throughout the state. Grizzlies were a dire threat to life and property, however, and were killed in large numbers. By the early 1900s, few grizzlies and little of their prime habitat in the Central Valley remained. The last California grizzly was killed south of Yosemite in the Sierra foothills in 1922, according to one account. Black bears, in contrast to brown bears, have fared much better due to a combination of their greater adaptability around people and habitat stability.

Black bears fascinate wildlife enthusiasts due to their curious physiology and behaviors. Most of Yosemite’s black bears, despite their name, are not black but are brown in color. Truly black black bears are rare in the Southwest. Black bears vary greatly in size— the largest black bear captured in Yosemite weighed 690 pounds, which is much larger than the typical male found here that weighs 300 to 350 pounds. Bears weigh the most in fall when gorging on acorns to gain fat to survive winter—consuming up to 20,000 calories a day. (That is a lot of calories, equating to a person eating 40 Big Mac sandwiches in a day.) Bears hibernate in hollow trees or logs, under the root mass of a tree, or in caves formed by the jumble of large rocks. While hibernating, bears enter a state of reduced body temperature, pulse rate, and respiration to conserve energy and do not defecate nor urinate but can metabolically extract energy from body wastes. Their “sleep” is not a deep one, which allows them to leave the den periodically. After emerging from winter dens, bears feed largely on meadow grasses, which are low in nutrition but sustain them until berries of various plant species ripen to provide higher calories. Bears also eat ants, termites, and insect larvae ripped out of logs or dug from the ground.

Visitors who encounter a bear should keep their distance out of safety and respect for themselves and the animal. If visitors see a black bear in undeveloped areas, they should remain at least 50 yards from it. If they encounter a bear in developed areas, they should stand their ground and scare the bear away by raising their arms and making loud noises. Black bears may show dominance by bluff charging, especially when guarding food or cubs. Attacks are rare, and no one has been killed by a black bear at Yosemite.

The Yosemite bear management team places signs where a vehicle-bear collision has occurred in the park to educate drivers to slow down.

Park managers attempt to preserve this species that can be negatively affected by humans. First, visitors should drive the speed limit, reminded by signage placed where a bear has been hit by a vehicle. Next, visitors should avoid poor food storage practices. Management efforts by groups like the Wildlife Conservation Society study how to better make humans aware of their actions. (Academic Reports: Read about human-bear interaction.)

Bear management attitudes have changed since the early days of the park's history when little was done to keep bears from becoming conditioned to human food. Decades ago, the National Park Service maintained several bear feeding areas in the park where bears were fed for entertainment reasons.

When visiting, visitors should expect black bears to attempt amazing acts to obtain human food. If food has been left in a car, bears will break vehicle windows, bend car frames, and pop open camper shells. To get into a trunk, they will enter the passenger area and claw through the back seat. Learn about Yosemite’s bear management and food storage regulations for campgrounds, trailheads, lodging and wilderness.

Source (more on Bear Management page):

• Mazur, R. & Seher, V. (2008). Socially Learned Foraging Behaviour in Wild Black Bears, Ursus Americanus, The Association for the Study ofAnimal Behaviour, 75: 1503-1508. [166 kb PDF]

To Learn More

• Get up-to-date details of Yosemite's bear activity.
• See how to use bearproof food lockers located throughout the park.
• View a video on proper food storage for all visitors.
• Backpackers need to take additional precautions to ensure proper food storage. Canisters are required in all of Yosemite's backcountry.
• If you see a bear, file a wildlife observation summary report or e-mail sighting specifics with location details to the park.