Orang-utan

Orang-utans are more solitary than the other apes. Adult males interact with other orang-utans only to fight over responsive females and to mate. The most common social units are the mother and her immediate offspring, subadult males, and small groupings of adolescents of both sexes. Orang-utans are long lived (around 50 years) and have extensive intervals between births. Females mature at about 10 years of age and remain fertile until about 30 years old. Although there is no visible evidence of estrus, when a female is pregnant, her swollen, white genitalia are readily observable. Gestation lasts 264 days. The young orang-utan is totally dependent on its mother for food, protection, and transportation during its first year. The young are weaned at about three years and begin to climb and forage for their own food at age four. At six or seven years old, orang-utans reach sexual maturity and become independent of their mother.