<P> American black bears tend to be territorial and non-gregarious in nature . However, at abundant food sources (i.e. spawning salmon or garbage dumps) black bears may congregate and dominance hierarchies form, with the largest, most powerful males dominating the most fruitful feeding spots . 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 . On Long Island off the coast of Washington, ranges average 5 sq mi (13 km), whereas on the Ungava Peninsula in Canada ranges can average up to 1,000 sq mi (2,600 km), with some male bears traveling as far as 4,349 sq mi (11,260 km) in times of food shortages . </P> <P> Black bears may communicate with various vocal and non-vocal sounds . Tongue - clicking and grunting are the most common sounds and are made in cordial situations to conspecifics, offspring, and occasionally humans . During times of fear or nervousness, bears may moan, huff or blow air . Warning sounds include jaw - clicking and lip - popping . In aggressive interactions, black bears produce deep - throated pulsing sounds . Cubs may squeal, bawl or scream when in distress and make motor - like humming when comfortable or nursing . </P> <P> Sows usually produce their first litter at the age of 3--5 years, with those living in more developed areas tending to get pregnant at younger ages . 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 . 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 . 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 . </P> <P> The average lifespan in the wild is 18 years, though it is quite possible for wild specimens to survive for more than 23 years . The record age of a wild specimen was 39 years, while that in captivity was 44 years . The average annual survival rate for adult bears is variable, ranging from 86% in Florida to 73% in Virginia and North Carolina . In Minnesota, 99% of wintering adult bears were able to survive the hibernation cycle in one study . Remarkably, a study of black bears in Nevada found that the amount of annual mortality of a population of bears in wilderness areas was 0%, whereas in developed areas in the state this figure rose to 83% . Survival in sub-adults is generally less assured . In Alaska, only 14--17% of sub-adult males and 30--48% of sub-adult females were found in a study to survive to adulthood . Across the range, the estimated number of cubs who survive past their first year is 60% . </P>

How long do black bears live with their mother