Black Bear Natural History, Distribution, and Status
The American black bear is a large-bodied, shaggy-haired mammal with small eyes, rounded ears, and short tail. In eastern North America, these bears are typically black overall with a brown muzzle and sometimes a white chest patch. Brown, cinnamon, and other color phases occur elsewhere. Their feet are large and well padded, with moderately-sized curved claws. The bear population has grown from about 100 in the early 1970s to about 3000 in 2005, in response to increased legal protection, changes in forest structure and composition, and increased availability of supplemental fall foods. Male black bears generally range in weight from 130 to 600 lbs. and females from 100 to 400. In Massachusetts, males averaged 230 lbs. and females 140. Lengths range from 3½ to 6 feet and shoulder height from 2½ to 3½ feet.
Black bears have good eyesight and hearing and have an extraordinary sense of smell which is used to locate food and recognize potential danger. They are excellent climbers and commonly use trees for resting and escape cover and to protect their young.
Black bears mate between mid-June and mid-July. The dominant male will breed several females. After breeding, the fertilized egg develops into a minute ball of cells ("blastocyst") which remains free-floating in the uterus for several months. If the female is well-nourished, the blastocyst implants in the uterine wall in late November and the small feeble cubs are born in the den in mid- to late January. Litter sizes range from 1 to 4 cubs, usually 2 or 3 in Massachusetts. Cubs exit the den in early to mid-April and remain with the mother for about 17 months, at which time she comes into estrus again and chases the yearling bears away. The young females typically take up residence near their mother's area but the young males disperse many miles. Females typically first give birth at 3 or 4 years, but this may occur later in northern boreal forests where food is scarce.
Massachusetts bears are typically active in daytime during spring and fall, but are more active during dawn and dusk hours in summer. Males may be nocturnal during the breeding season. Typical spring habitats in Massachusetts include wetlands with lush emergent vegetation and hardwood areas with leftover nuts from the previous fall. In summer, wetlands and cutover areas with emerging berry crops are preferred. Corn fields and oak, beech, or hickory stands are favored in fall. Bears have good long-term memory and are capable of recalling the location of periodic food sources years after the first visit.
In Massachusetts, adult females use home ranges averaging 9 to 10 mi² while adult males may have ranges exceeding 120 mi². Depending on food availability, Massachusetts bears enter the den between mid-November and early December and exit between early March and mid-April. Pregnant females often enter early and those with newborn cubs exit late. Bears commonly den in brush piles, under fallen trees or a jumble of rocks, or in a mountain laurel thicket.
Despite popular belief, black bears are not fierce. Their first response is usually to flee and in woodland areas the bears may disappear long before they are seen. Black bears sometimes can become habituated to human presence and conditioned to human food sources. These circumstances may then lead to damage or depredations which have unfortunate consequences if people then destroy the bear out of fear or to alleviate the damage. Black bears rarely harm people, although minor defensive attacks can occur when people tease or closely approach bears in parks or campgrounds. Female black bears defend their cubs by putting them up a tree. The sows may huff and blow and make short rushes at people who get near the cubs, but will almost never press home an attack. Deliberate predatory attacks are very rare and typically occur in remote areas.
American black bears are found in most of Canada south of the tree line and still occupy 85% of their original range there. They are found in 43 states and are abundant or common in 29 of them. Black bears have recently reoccupied much of their original range in the U.S., especially in the east, and their status is generally favorable. They are still uncommon in parts of the midwest. Black bears are endangered in Mexico. In Massachusetts, black bears have been increasing in numbers and distribution for the past 30 years. They are common in western Massachusetts, moderately common in the central region, and rare or absent in the eastern counties.