Orangutans are semisolitary and don't form monogamous couples as humans do. Adults generally live alone or in loose association with either relatives or animals of the same gender and age. Female orangutans mate with a number of different males when they are in heat, although they prefer to mate with dominant males and actively seek out the dominant male nearest to their own territory.
Sometimes breeding couples form consortships after mating, but these associations last at most a few months. After breeding, an orangutan mother cares for its baby for 6 to 9 years, during which time it doesn't mate. Males don't participate in child care. Orangutans become sexually mature at 12 years of age for females and 15 years for males. Fully mature males have large cheek sacs called flanges, but not all males form flanges as they age. It is the fully mature, flanged males with territorial dominance that females prefer. Sexually mature, unflanged males are nomadic until they can displace dominant males and form their own home territories. Until that time, these nomadic males sneak into the established territory of dominant, flanged males and forcibly mate with any females in heat. Mates find one another through the use of calls and scents.