Female black bears typically begin having cubs at three to five years of age. Females as young as two years of age may reproduce in high quality habitats. Conversely, females in marginal habitats may not produce young prior to their seventh year.  

Mating generally occurs in the summer months and egg implantation is usually delayed for about five months.

Cubs are born in winter dens in January and February.   Food availability prior to the denning season has a significant bearing on litter size.  Although two or three cub litters are most common, litter sizes range from zero to four, depending on the age and condition of the female.  

Cubs are born in a helpless state. Measuring about eight inches in length and weighing eight to twelve ounces, they develop and grow rapidly largely because of the richness of a mother bear’s milk. The sex ratio at birth is usually one male to one female.

Mother and cubs leave the den in April or May when the young weigh from four to eight pounds. The cubs stay with their mother through the first year, which includes sharing a winter den. 

In mild winters, with residual food sources available, it is not uncommon for the family unit to remain active through the winter. 

Mother and cubs emerge again in the spring, and live with her until the summer when the family unit dissolves. Male offspring tend to disperse, while females remain nearby.  When the family unit dissolves, the female then goes back into estrus, breeds, and repeats the cycle.