Reproduction in chimpanzees is similar to humans. At this stage, the average number of infants a female can produce in a lifetime is not known. Chimpanzees are considered to be a K-strategist species, meaning they have delayed onset of reproduction and produce few, large young in which the parents invest heavily. K-Strategists are often unable to rebuild their populations fast enough to avoid extinction following a major decline in population numbers.
Copulation can occur at any point in the females oestrous cycle. Males may guard females from mating with other males. This can cause tension amongst males, and in some cases consortship behaviour will be observed; the male entices a female to leave the core area and they travel together away from the other community members until her cycle has completed.
Menstrual cycles last on average 39.8 days for young nulliparous females (those who have never borne a child) and 33.8 days for older multiparous females (those who have borne more than one child). Females exhibit their first sexual swellings at around 10-11 years, with an average swelling of 12-13 days. Duration of gestation ranges from 208 days to 235 days, with an average of 225.3 days. Mating is generally promiscuous although consortship’s involving just one male and one female have been recorded. Inter-birth intervals range from 3-7 years. The longest ongoing field study of chimpanzees is Jane Goodall’s research station in Gombe Stream National Park, with continuous observation of a wild chimpanzee community spanning 45 years. Some of the females that were born at the time of Jane Goodall’s arrival are alive and still reproducing. This suggests that wild living chimpanzees may go through menopause at a much later age than first thought. Several female chimpanzees in captivity that are no longer cycling are all over fifty years of age.