Black bears are very opportunistic eaters. Most of their diet consists of grasses, roots, berries, and insects. They will also eat fish and mammals—including carrion—and easily develop a taste for human foods and garbage. Solitary animals, black bears roam large territories, though they do not protect them from other bears. Males might wander a 15- to 80-square-mile (39- to 207-square-kilometer) home range.
The skulls of American black bears are broad, with narrow muzzles and large jaw hinges. In Virginia, the total length of adult bear skulls was found to average 262 to 317 mm (10.3 to 12.5 in). Across its range, greatest skull length for the species has been reportedly measured from 23.5 to 35 cm (9.3 to 13.8 in). Females tend to have more slender and pointed faces than males. Their claws are typically black or grayish brown. The claws are short and rounded, being thick at the base and tapering to a point. Claws from both hind and front legs are almost identical in length, though the foreclaws tend to be more sharply curved.
A black bear has better eyesight and a better sense of hearing compared to humans. Their keenest sense is the sense of smell, which is about seven times greater than a dog’s. American black bears tend to be territorial and non-gregarious in nature. They mark their territories by rubbing their bodies against trees and clawing at the bark. Annual ranges held by mature male black bears tend to be very large but there is some variation.
Black bears climb regularly to feed, escape enemies and to hibernate. Half of bear species are habitually arboreal, abilities tend to decline with age. Black bears may be active at any time of the day or night, although mainly forage by night. Bears living near human habitations tend to be more extensively nocturnal and bears living near brown bears tend to be more extensively diurnal.
Black bears do compete with cougars over carcasses. Like brown bears, they will sometimes steal kills from cougars. One study found that both bear species visited 24% of cougar kills in Yellowstone and Glacier National Parks, usurping 10% of carcasses. Fights between the two species are rare, though they can be violent. Cougars occasionally kill adult bears, a behavior reportedly witnessed in the 19th century. There are also 19th and early 20th century records of bears killing cougar, either in defense or in territorial disputes, and occasional fights which ended in both combatants fatally wounded.
Black bear interactions with wolves are much rarer than with brown bears, due to differences in habitat preferences. The majority of black bear encounters with wolves occur in the species′ northern range, with no interactions being recorded in Mexico. Despite the black bear being more powerful on a one to one basis, packs of wolves have been recorded to kill black bears on numerous occasions without eating them. Unlike brown bears, black bears frequently lose against wolves in disputes over kills. Wolf packs typically kill black bears when the large animals are in their hibernation cycle.