Africa Baboons can thus use their habitat more efficiently than chimps do, and this enables a fairly large troop of baboons to stay together all the time and to range over a very small area. 60 baboons can find all they need within 2 sq km, while 60 chimps need an area at least ten times as large to feed them all year round. At Gombe, several troops have been studied since 1967. Researchers can distinguish individuals by variations in face, build, shape of tail etc. and have followed the development and relationships of many baboons throughout their lives. Troops consist of about 20-70 individuals with a roughly equal sex ratio.
Females form the stable core of the troop, all males emigrate to other troops when mature.
Thus the social bonds between the females, who have grown up together and who are closely related, are more stable than those between the males of a troop, who may first have met as adults. In fact, new males seem to join a troop by first making friends with a female, and then fighting for a place in the male hierarchy. The males of a troop compete intensely for status and access to females. A female has an oestrous cycle of 30-35 days, and for about 2 weeks around the time of ovulation she displays a pink sexual swelling. She may mate promiscuously, but at the time of ovulation, she tends to form a consortship with a single mature male, or with several in succession.