Young females learn to be mothers by watching their mothers and helping with younger siblings. Young males follow around after adult males, spending less and less time with their mothers as they grow older. At 13 to 15 years of age, chimpanzees spend most of their time with adult males and females in estrus. For females, late adolescence begins with the onset of estrus cycles and adolescent sterility and ends with the ability to reproduce. Some females transfer to another community for a brief period, and reproduce with males in that community. Chimpanzees are mature at 16 to 20 years of age; old age begins at 33 years in the wild. Wild chimpanzees may live to be 40 or 50 years old or more.
Jane's observation:
Some chimpanzees, like some humans, develop faster than others; moreover, the behavior
of a chimpanzee's mother undoubtedly has a marked effect on his physical and social development: the same holds good
for human mothers, too. A mother (chimp or human), for instance, may be permissive or restrictive toward her child's
early attempts to walk; she may be tolerant or nervous about his initial contacts with others of his kind. The ages
given here for the appearance of the different physical or social developments in chimpanzees are the earliest at
which they were observed in any of our youngsters. Month 2 refers to the second month of life: i.e., the infant is
between 4 and 8 weeks of age. Similarly, year 3 refers to youngsters between 24 and 36 months of age.
Behavior
Month First Seen
Sucks thumb
Mother may tickle occasionally and briefly
Stares at object; reaches toward it
Struggles to pull from mother
Stands upright holding on to mother
Pushes and pulls itself forward on mother’s body
Reaches toward object and grasps, showing coordination
First tooth
Mother plays frequently and for longer at a time
Infant shows play-face and laughing during tickling
Chews and swallows first piece of solid food
Reaches to play with mother’s hand during game
Starts to ride on mother’s back *
Takes first step
Mother-infant contact broken
Climbs up sapling or branch
Kidnapped (a sibling may kidnap earlier, during 4th month)
Kisses another
Attempts to groom another, inefficiently
Attempts to make nest
Attacked mildly by another
Mounts and thrusts “pink” female
Runs at and hits another infant aggressively
Reassures another in correct context
Grooms with adult technique
Charging display and rain dance in correct context
Violent attack on another youngster
Attempts tool-using in correct context
Weaned
Starts to lose milk teeth
May start to move around for short periods without mother
Attains puberty
First infant born
Male becomes fully socially mature
3 (early)
3 (early)
3 (early)
by end of 5
6
6
about 8 or 9
about 11 or 12
about 15
* One infant (Pom) rode in the dorsal position at 8 weeks; this was unusual
and was because she hurt her foot.
