Mother chimpanzees care for their offspring for several years with infants totally dependant on their mothers for 6-8 years and sometimes even longer as they mature and become independent. This extremely close physical and emotional relationship is very similar to humans and, when broken, leads to severe trauma and grief. A mother chimpanzee will fight to the death to protect her baby from other chimpanzees, wildlife or humans.
Infant and juvenile chimpanzees spend much of their time playing each day with other young ones as well as with adults in the group. Chimpanzees make play faces and body language similar to that of humans and even laugh out loud. Play includes tickling, wrestling, chasing and other games and sometimes incorporates objects such as leafy twigs, sticks, stones and fruit.
Reproduction in chimpanzees is similar to humans although the average number of infants a female produces in a lifetime is not clear. Chimpanzees are considered a K-strategist species, having a delayed onset of reproduction and producing few young in which the parents invest heavily. K-Strategists are often unable to rebuild their populations rapidly enough to avoid extinction following a major decline in population numbers.
Copulation can occur at any point in a female’s estrous cycle. Males may guard females from mating with other males, causing tension amongst males and, in some cases, courtship behavior will be observed. Males entice females to leave the core area and travel with them away from other community members until their cycles have finished.
Menstrual cycles last on average 40 days for young females who have given birth and 35 days for older females who have given birth at least twice. Females exhibit their first sexual swellings at around 10-11 years, with an average swelling of 12-13 days and a gestation period of between 200 to 235 days. Mating is generally promiscuous although courtship involving just one male and one female has been recorded. Inter-birth intervals range from 3-7 years. Gombe Stream National Park in Tanzania has the longest running field study of chimpanzees. Researchers have been continuously observing the same community of wild chimpanzees for 50 years. Some of the females born during the start of Gombe’s research site are still alive and reproducing, suggesting that wild living chimpanzees may go through menopause at a much later age than initially thought.