Bears are mammals and therefore reproduce sexually, The male deposits sperm from his penis into the vagina of the female bear. If the egg becomes fertilized, the female bear gives birth to live young. The average number of cubs in a black bear litter is three, but first-time mothers usually only give birth to one cub.
After the eggs become fertilized as a result of copulation, they quickly become tiny balls of cells that are referred to as blastocysts. These do not implant themselves into the wall of the uterus until just prior to hibernation. If the female bear has not developed a sufficient amount of fat stores, the blastocysts fail to implant.
Bears are solitary animals that only come together during mating season, which starts in May and continues through the early part of July. The average age for a female bear to mate for the first time is 3 1/2 years. Most male bears reach sexual maturity at the same time as their female counterparts. However, males rarely have the opportunity to breed until they are older because larger, more mature adult males offer steep competition for available females. Females usually bear litters in two-year cycles.
Bear cubs are born during the month of January and stay with their mother in the den until spring. Cubs stay with their mothers for around 17 months. During this time, they learn to forage for berries, catch fish, scavenge and otherwise fend for themselves. When it is time for the mother bear and her cubs to part ways, the mother often physically attacks the cubs to drive them away.