Copulation normally lasts 20 to 30 minutes, but may last up to one hour or more.Įstrus females are frequently pursued by more than one male. The act itself is repeated many times, each time it takes only a matter of seconds, but the pairs stays locked together (sometimes breaking for a nuzzle or bite on the neck/back or just walking about) until the next bout. During mating, the male and female become almost inseparable, mating repeatedly in the ensuing days. When contact is made, the bears nuzzle and chew on each other’s head and neck and may even wrestle a little.Īlthough the female is in heat for a number of weeks, she will only allow a male to mount her when she is most receptive, during the three to five day period in the middle of her estrus cycle. Males rarely retaliate, but bide their time. If she is afraid – males are bigger and potentially dangerous – she may charge him or swat him with her paw, especially if it is her first time. But in time she allows him closer and closer. At first, she may run away, playing hard to get. Initially, a male suitor trails his prospective mate from a distance, smelling her daybeds and sniffing her urine to analyze how receptive she is. A male and female bear may spend days courting each other before mating. Sub-adult males, on the other hand, are usually discouraged from staying and must travel often large distances to establish a home range.ĭuring spring when roaming males begin courting reproductive aged females, mothers are often forced to break up the family unit, in order to protect their cubs from infanticide. Sub-adult females tend to establish home ranges within or overlapping their mother’s home range.
Alone and vulnerable, siblings will often stay together for some time after their mother leaves them, eating and sleeping side-by-side, and even denning together. Mothers will tenaciously reject their offspring if they try to return. The mother that protected and cared for them just yesterday has cast them aside. Stressed and frightened, they whine and whimper in disbelief. It’s heart-breaking to watch a mother break up her family. Depending on food abundance, mothers (especially grizzlies) may keep their yearlings a second (even a third) year, denning together again and breaking up in the third (or fourth) year. Mother bears tend to be affectionate, protective, devoted, strict, sensitive and attentive toward their cubs, raising them to an age where they can survive on their own. Once they have left the womb, they find their way to their mother’s teats where they feed on milk (and grow) until the spring. Cubs weigh one-tenth as much as human babies and are born blind. Litter size ranges from one to six, depending on the species and the productivity of the surrounding habitat. If the female does not attain sufficient body fat or weight during the summer and fall, the embryos will not attach to the uterine wall and subsequently develop into little bears.Ĭubs are born in the den in January or February. The implantation of the fertilized eggs – called blastocysts – is delayed until the start of denning season. Not only are male bears promiscuous, but females often have more than one mating partner.īreeding season begins in May and lasts until early July, with mating mainly occurring during June. The biggest bears in the population tend to be the most prolific breeders. Even though males are capable of breeding at three or four years of age, they rarely have the opportunity to do so because of intense competition from older, bigger males. Males reach sexual maturity at roughly the same age as their female counterparts. The average breeding age for female black bears is 3.5 years and for female grizzlies is 4.5 years. By comparison, a pair of white-tailed deer could produce more than 1,400 descendants in 10 years.īears generally live solitary lives, but can be found together during mating season. Grizzly bears are even less productive: in 10 years, a male a female born today could grow to a population of only eight.
In theory, a male and female black bear born this year – if they breed as soon as they reach sexual maturity and as often as possible, and if all their offspring survive to do the same – could in the space of ten years have grown to a population of 15 bears (assuming none died). Bears are among the least productive mammals in North America.