The Mating Game

Breeding occurs between late May and early July, with the greatest activity in June. Bears generally live solitary lives, but can be found together during mating season. The breeding age for female black bears is 3 ½ years and female grizzlies is 4 ½ years. Males reach sexual maturity at roughly the same age as their female counterparts. Eventhough males are capable of breeding at 3 or 4 years of age, because of intense competition, they rarely have the opportunity to do so. The biggest bears in the population tend to be the breeding contenders. Not only are male bears promiscuous, but females often have more than one sexual partner.

Adult mothers with yearlings often break-up the family unit in the spring initiating the courtship and mating season. Depending on food abundance, mothers (especially grizzlies) may keep their yearlings a second year, denning together again and breaking up in the third year.

A mother raises her cubs to an age where they can survive on their own. It's heart breaking to watch a mother break up her family. The cubs are completely distraught. Stressed and frightened, they whine and whimper in disbelief. The mother that protected and cared for them just yesterday has cast them aside. Mothers will tenaciously reject their offspring if they try to return. Alone and vulnerable, siblings will often stay together for some time after their mother abandons them, eating and sleeping side by side, and even denning together. Daughters are allowed to remain within their natal range, while sons are normally forced to leave their mother's territory.

By breaking apart the family, females become receptive to mate with roaming males. A male and female bear may spend days courting each other before mating. Initially, a male suitor trails his prospective mate from a distance, smelling her day beds and sniffing her urine to analyze how receptive she is. At first, she may run away, playing hard to get. But in time she allows him closer and closer. If she is afraid - males are bigger and more dangerous - she may charge him aggressively or swat him with her paw, especially if it is her first time. Males rarely retaliate, but bide their time. When contact is made, the bears nuzzle and chew on each others head and neck and may even wrestle a little.

Although 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 3-5 days in the middle of her estrous period. During mating, the male and female become almost inseparable, mating repeatedly in the ensuing days. Copulation normally lasts 20-30 minutes, but may last up to one hour.

The female ovulates only after she has found a mate and has been appropriately stimulated. The male has a bone in his penis called a baculum. In a large bear the baculum is about the size of a small cigar, providing the additional stimulation the female requires for induced ovulation.

Estrous females are frequently pursued by more than one male. If another male arrives during the courting ritual, the males may challenge one another for dominance or they may fight if they appear evenly matched.

Infanticide among bears is a cruel reality. Boars that encounter sows with cubs will sometimes kill the cubs to initiate breeding and perpetuate their bloodlines. Sows, especially grizzlies, are very protective of their young and will fight back fiercely. The males responsibility ends with copulation. They do not participate in the rearing of offspring.