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. Black bears are very smart and curious animals. They 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. As of November 2026, the National Park Service says black bears have an incredible sense of smell, about seven times stronger than a bloodhound's, although they can see and hear well enough.
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, mostly in forests and other places with trees. 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. 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.
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. In a California hair-snare study, researchers collected 469 hair samples at 57 of 90 hair-snare locations during a 50-day period in summer 2018.
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. Males reach sexual maturity at 3 to 4 years but keep growing until they are 10 to 12 years old. 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 the Alaska 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. After the bears woke, their metabolism stayed low for several weeks even though body temperature returned to normal quickly.
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
- metabolism: body's energy use
- implantation: egg settling in
- Carnivora: meat-eater order
