Baby bears are called cubs. Gestation typically lasts 6–9 months, including delayed implantation, and litter size numbers up to four cubs. Giant pandas may give birth to twins but they can only suckle one young and the other is left to die. In northern living species, birth takes place during winter dormancy.
Cubs are born blind and helpless with at most a thin layer of hair, relying on their mother for warmth. The milk of the female bear is rich in fat and antibodies and cubs may suckle for up to a year after they are born. By 2–3 months, cubs can follow their mother outside the den. They usually follow her on foot, but sloth bear cubs may ride on their mother's back.
