Under most circumstances, brown bears live as lone individuals, with few exceptions, one being females accompanied by their cubs as pictured here. Female bears become sexually mature between 5 and 7 years of age. Mating normally takes place during the spring from May to June. Brown bears will stay with the same mate from a few days to several weeks. Female bears will continue to produce cubs throughout their lives with an approximate 4 year interval between litters. The average number of cubs born is two to three, though four is not unusual. Age, geographic location and food supply influence the size of a bears litter. The number of cubs a female will have increases, as she gets older. At birth, they are blind, toothless and weigh less than one pound. The bears pictured in the inset are young sub adults and siblings. These bears will often stay together for several years after being seperated from their mother until they are between 5 and 7 years of age at which time they will be ready to mate.