where are brown bears found in the us
Brown bear The brown bear has lost 98% of its habitat in the lower 48 states. About 95% of the brown bear population in the United States is in Alaska, though in the lower 48 states, they are repopulating gradually but steadily along the Rockies and the western Great Plains.[144][145] The Alaskan population is estimated at 32,000 individuals.[146] The largest populations of brown bears in the lower 48 states are found in the 23,300-km2 Greater Yellowstone Ecosystem and the 24,800-km2 Northern Continental Divide Ecosystem.[147] The Greater Yellowstone Ecosystem of northwest Wyoming is estimated to hold about 674–839 grizzly bears, followed slightly the Northern Continental Divide Ecosystem of northwest Montana with about 765 animals, the Cabinet-Yaak Ecosystem of northwest Montana and northeast Idaho with about 42-65 bears of the species, the Selkirk Ecosystem of northeast Washington and northwest Idaho with only about 40–50 animals and even less the North Cascades Ecosystem of northcentral Washington with about 5–10 grizzlies.[148][149][150][151] These five ecosystems combine for a total of a maximum 1,729 wild grizzlies still persisting in the contiguous United States. Unfortunately, these populations are isolated from each other, inhibiting any genetic flow between ecosystems and creating low genetic diversity in remaining populations which can have negative long-time effects.[147][152] This isolation poses one of the greatest threats to the future survival of the grizzly bear in the contiguous United States.[147] Although there is no record of their existence in the United States east of the Rocky Mountain and Great Plain regions in human history, fossil records from Kentucky and the Ungava Peninsula do in fact show that grizzly bears once roamed in eastern North America.[153]
American black bear Sows usually produce their first litter at the age of 3–5 years,[35] with those living in more developed areas tending to get pregnant at younger ages.[61] The breeding period usually occurs in the June–July period, though it can extend to August in the species' northern range. The breeding period lasts for 2–3 months. Both sexes are promiscuous. Males try to mate with several females, but large, dominant ones may violently claim a female if another mature male comes near.[32] Sows tend to be short-tempered with their mates after copulating. The fertilized eggs undergo delayed development and do not implant in the female's womb until November. The gestation period lasts 235 days, and litters are usually born in late January to early February. Litter size is between one and six cubs, typically two or three.[62] At birth, cubs weigh 280–450 g (0.62–0.99 lb), and measure 20.5 cm (8.1 in) in length. They are born with fine, gray, down-like hair, and their hind quarters are underdeveloped. They typically open their eyes after 28–40 days, and begin walking after 5 weeks. Cubs are dependent on their mother's milk for 30 weeks, and will reach independence at 16–18 months. At the age of six weeks, they attain 900 g (2.0 lb), by 8 weeks they reach 2.5 kg (5.5 lb) and by the age of 6 months they weigh 18 to 27 kg (40 to 60 lb). They reach sexual maturity at the age of three years, and attain their full growth at 5 years.[35]