Black bears and other members of the bear family are understood to have evolved from a common ancestor about 4 to 7 million years ago, in a burst of new species. Based on mitochondrial DNA, the American black bear's closest relative is the Asiatic black bear. Genetic studies suggest two lineages of black bears, one along the western coast and one in the continental region, which split about 1.8 million years ago. Scientists list subspecies of the American black bear that include the cinnamon bear, the glacier bear, the Florida black bear, the Newfoundland black bear, the Kermode or spirit bear and the Louisiana black bear.
Black bears have one of the largest relative brain sizes in the order Carnivora, compared with families such as dogs, cats and weasels. In tests, black bears were able to tell different numbers of objects apart at a level at or above that of great apes, and they performed at a level equal to great apes in learning abstract concepts, such as telling photographs of animals from photographs of non-animals. Black bears are very smart and curious animals.
It is not well understood why black bears mark trees, and it has been debated whether the marks pass on social information, like territorial marking in other carnivores.
Counting bears takes DNA. Biologists in Missouri stretch barbed wire around trees to make a hair snare, and hair that catches on the wire is sent to a lab for DNA analysis that shows how many individual bears were detected. Wyoming Game and Fish builds a hair snare from a ring of barbed wire about knee high around some trees, about 20 feet across, with scent in the middle. A California wildlife study used hair snares to collect hair for DNA, and its lead scientist called this the gold standard for counting American black bears. A USGS-published study of a 2006 hair-snare survey in northern New York identified 47 individual bears from DNA and estimated a mean density of 0.20 bears per square kilometer.
The black bear is the most common and most widespread bear in North America, and it lives across much of the continent, from Alaska and Canada through the United States to Mexico. As of November 2026, biologists summarizing regional estimates put the total number of black bears in North America at 850,000 to 950,000, and there are more black bears than all other bear species in North America combined. As of November 2026, Alaska has an estimated 100,000 black bears, and roughly 1,900 live in Great Smoky Mountains National Park. By the 1850s almost 75 percent of Vermont's land was cleared for farmland, and its black bears were at their lowest numbers then. Over the 20th century, wildlife protection laws, stricter hunting rules and protection of remaining habitat allowed black bear populations to recover to stable or increasing levels across much of their range. A 2016 federal rule removed the Louisiana black bear from the list of endangered and threatened wildlife because the subspecies had recovered. Missouri's black bear population has grown from about 300 to nearly 1,000 since 2011, as of October 2024, and California estimated about 35,000 black bears in 2018, up from an estimated 10,000 to 15,000 in 1982.
Researchers say climate change may not hurt most black bear populations because they are adaptable, but because female bears do not spread far, black bears may not move well to new areas as habitat shifts.
The black bear is the smallest of the bears that live in North America. On average, adult female black bears weigh 40 to 70 kilograms and adult males 60 to 140 kilograms, depending on how rich their habitat is. In a long-term summary, adult male black bears are typically 15 to 25 percent longer and 10 to 70 percent heavier than adult females. The average home range of a male black bear is usually 3 to 8 times larger than that of an average female. As of November 2026, the average home range reported for Tennessee is 6.9 square kilometers for females and 51.2 for males; in Alaska, 65.8 for females and 218.5 for males.
Black bears eat both plants and animals. What a black bear eats changes with the seasons: grasses and other green plants in spring, berries in summer, and nuts in fall. In many places only a small part of what black bears eat is animal matter, mostly colonial insects and grubs. Black bears are not active predators, and they eat other animals mainly when the chance comes. They prefer salmon, elk calves or deer fawns in places and seasons where these foods are plentiful; they help spread the seeds of the plants they eat. In fall, black bears eat a lot of fruits and nuts to build up fat for the winter, and they may travel long distances to find food. Spring, when they come out of their dens, is a hard time to find food.
Black bears spend the winter in dens, and a black bear may hibernate for five to seven months of the year. The International Association for Bear Research and Management says a black bear's winter dormancy lowers its body temperature by 7 to 8 degrees Celsius, cuts its metabolism by 50 to 60 percent and slows its heart to 8 to 19 beats per minute. During dormancy, black bears do not urinate or defecate and appear to lose very little muscle or bone despite months of inactivity. A study of Alaskan black bears found their metabolism fell by 75 percent compared with summer, to about 25 percent of their active rate, and their heart rate slowed from about 55 beats a minute in summer to about 14 beats a minute. In that study, the bears' body temperature cycled between about 30 and 36 degrees Celsius over cycles of two to seven days, which scientists had not seen in other hibernators, and after the bears woke, their metabolism stayed low for several weeks even though body temperature returned to normal quickly. Chemical and biological processes in a body are known to slow by about 50 percent for each 10 degrees Celsius drop in body temperature, but the Alaskan black bears lowered their core temperature by only five or six degrees and their metabolism slowed far more. As of November 2026, how a large mammal like a black bear can hibernate at all is still not fully understood, and scientists continue to study it.
After mating in summer, the black bear's fertilized egg does not start to grow until fall. Delayed implantation lets a female black bear avoid spending fat and energy on a pregnancy that would have little chance of success because her condition is too poor; black bear cubs are born in winter, in the mother bear's den. Newborn cubs are blind and have almost no hair, and they are among the smallest babies, compared with their mother's size, of any mammal. Newborn cubs make humming sounds while nursing, which is a sign they are satisfied. The cubs stay in the den with their mother all winter, and she feeds them. A mother black bear most often has two cubs at a time, and she has cubs every other year when there is enough food; adult black bears usually live alone, but a mother stays with her cubs. Cubs stay with their mother for about a year and a half, and they go into the den with her again the next winter.
Words to know
- dormancy: winter rest
- lineages: family lines
- metabolism: body's energy use
- implantation: egg settling in
