Yosemite National Park - Black Bears

Overview
Yosemite National Park is home to 300 - 500 American black bears, Ursus americanus . Although usually referred to as the black bear, very few are black, and they are more likely to be found in a variety of colors ranging from black to brown, blond, or cinnamon.

Feeding habits
Black bears are omnivores and will eat almost anything. They spend most of their days foraging for grasses, seeds, berries, acorns, and insects and occasionally feed on carrion. Bears tear open rotten logs or old stumps in search of insect larvae. Meadows also furnish a wide variety of food, such as grass, clover, lily, wild onion, and brodiaea bulbs. Research in Yosemite shows that plants, including acorns, comprise 75% of the diet of Yosemite bears. Bears are also fond of fruit, particularly manzanita, service berry, elderberry, and wild cherry. Chipmunks, ground squirrels, marmot, pocket gophers, and mice are also a part of their diet. In the fall, bears are often seen beneath oak trees searching for acorns. Unfortunately, many Yosemite bears have also perfected the skill of obtaining food from humans.

Bears are also opportunists which means that they can easily adapt to new foraging habitats--from meadows to manzanita bushes, from cars to picnic coolers. Opportunism is often seen as an indication of intelligence in animals and most researchers agree that bears are highly intelligent. Anyone who has lost food to a bear learns that a bear"s strength and intelligence should never be underestimated. This enterprising nature of the black bear can be linked to the fact that cubs stay with their mothers for well over a year after birth. This allows mother bears time to teach cubs survival techniques that directly relate to opportunism. It is this characteristic which allows cubs to learn from their mothers how to break into cars for food.

The biggest threat to the survival of the black bear in Yosemite is the availability of human food--in cars, campgrounds, picnic areas, and the wilderness. Once a bear is rewarded by obtaining human food, it will often continue to seek it out and some may even resort to intimidating humans in order to get more. As their natural fear of people fades, they may become more aggressive. When they become too aggressive and human safety is threatened, bears are sometimes killed by park rangers.

Obtaining human food alters the natural foraging habits, population dynamics, biology, and behavior of bears. It is the ultimate goal of wildlife managers is to have all bears in Yosemite eating their natural diet, avoiding humans and our food altogether. It is your responsibility to store food properly when visiting Yosemite. Your actions can affect the lives of bears!

Bear biology
Black bears reach sexual maturity at the age of three. Males and females stay together for only a few days when mating occurs in June or July. Although black bears have a gestation period of seven months, females do not show signs of pregnancy until shortly before birth because they have a reproductive adaptation called delayed implantation. The fertilized egg does not attach to the females" uterine wall until autumn. If food is scarce and a female is unable to put on sufficient weight before hibernation, the fertilized egg will, as a result, spontaneously abort.

A black bear litter consists of one to three cubs weighing as little as half a pound each. The cubs immediately begin to nurse on the female"s high fat milk and emerge from the den in early spring weighing as much as five pounds. The average adult bear stands three feet at the shoulder, measures five feet in length, and weighs between 200 and 300 pounds. However, some of Yosemite"s bears have tipped the scales at over 650 pounds!

During winter months when food sources are scarce, Yosemite"s black bears den in boulder caves and occasionally in the cavities of large trees. By metabolizing the body fat stored throughout the previous summer and fall they keep themselves warm. Black bears in the Sierra Nevada do not truly hibernate, since their body temperature and respiratory rate drop only slightly. Studies show that black bears, in general, have the ability to sleep for over five months without eating or eliminating waste.

The rising temperatures of spring and summer make it necessary for bears to concentrate on keeping themselves cool rather than warm. To stay cool, bears construct day beds or nests, usually in shady thickets or boulder piles. Much like dogs, they push aside leaves and twigs as they dig down to cool mineral soil. Black bears are most active during the crepuscular hours of the day, that is, dawn and dusk. During the warmest summer months, few bears are active during the day, becoming more and more nocturnal as summer temperatures rise. Many bears have found this cool, quiet time period to be the easiest opportunity in which to forage for natural foods, and search for human food because less people are present.

Black bear management: a look at the past and future
Perhaps no more than five bears co-existed within the granite walls of Yosemite Valley prior to the settlement of non-native people. But after more settlers and visitors began to live in and visit Yosemite, it was common to see as many as 60 bears at a time rummaging through garbage at a popular spot called Bear Hill. Back then, Yosemite bears were fed by rangers. The visitors who photographed them saw the bears as being synonymous with the park, and the bears themselves were quick to learn that human contact meant food.

In the 1920s and 1930s, human-conditioned bears were beginning to wreak havoc, injuring tourists and raiding restaurants nightly. In 1925, the National Park Service began luring bears away from restaurants and campsites with a trail of food scraps leading to open pit garbage dumps. This bear feeding program also attracted tourists who wanted to view bears close up. Responding to visitor demand, the National Park Service then designated a parking area and constructed bleacher seating at the dump in Yosemite Valley. Bear related injuries increased as people made attempts to get too close.

During the 1950s and 1960s, most of the open dumps in the Valley were closed due to the increased aggression by bears, which resulted in numerous visitor injuries. In 1971, the last dumps in the park were permanently closed. Bears learned quickly that they could get food from visitors staying in campgrounds, tent cabins, and the wilderness. In 1975, the National Park Service began a more comprehensive bear management program including research, public education, better methods of storing trash, and controlling problem bears. Many conditioned bears were killed by the National Park Service during the first years of this management program. Killing bears that had become conditioned to human food was the only way to decrease dangerous bear incidents. They could not be shipped off to zoos--which were more interested in exotic species--nor relocated outside the park, because surrounding U.S. Forest Service land managers and private owners did not want to deal with Yosemite"s conditioned bears.

Unfortunately, many park visitors fail to understand the connection between leaving food for bears--in cars, unattended in campsites, in backpacks--and killing them. Widespread noncompliance with food storage regulations causes bears to become conditioned to human food, and to become a threat to human safety. Currently, food-conditioned bears are captured, tagged, and relocated to more remote bear habitat within the park. Most of these bears find their way back, usually within one week. Bears that continue to return and exhibit aggressive behavior must often be euthanized. A new strategy has been to release the bears where they were captured while subjecting them to a very negative experience. The hope is that the bear will associate that area with the negative experience and avoid it.

The goal of wildlife managers is to provide the park"s black bears a home where they can thrive in a natural condition, dine on native plants and animals, and reach a normal life expectancy. To achieve this, one thing must happen in Yosemite: all human food, scented items, and garbage must be properly stored where bears cannot get them. This goal has been made possible with the help of the Yosemite Fund, which over the past 10 years, has donated food storage lockers for every park campsite, trailhead, parking lot, and rental tent camp. In 1998, the Yosemite Association launched a backcountry food storage program, and provided food canisters for hikers at a nominal rental fee. This program was expanded in 1999 when the Yosemite Association and DNC Parks & Resorts at Yosemite (then called Yosemite Concession Services) combined efforts. Now, every backpacker who leaves from a Yosemite trailhead will have access to a canister for a $5.00 per trip rental fee. Also in 1999, Yosemite National Park received a budget increase of $500,000 to increase visitor education, enforcement of food storage regulations, cleanup of trash, and additional wildlife management staff to work with bears. Since 1999, incidences of bears obtaining human food have plummeted, in large part because of increased cooperation of park visitors in storing their food and trash properly. (See how you can help .)

As for the future of black bears in Yosemite, some look forward to a day when seeing bears in developed areas is a rare occurrence. So, just as some people marvel that one could see bears at dumps in the park, perhaps some day people will marvel that bears used to walk through campgrounds and parking lots. Instead, those same visitors will hopefully see wild bears in their natural settings.