One Chimpanzee I have a lot of respect for is Nkombo. Nkombo has never had children, she is one of two females in the community that has always been barren.
Similar to humans, Chimpanzees cannot become pregnant while lactating or breast feeding, its got to do with a hormone that the body produces when they breast feed regularly. On average a female Chimpanzee will breast feed for 4 or 5 years which means they will not come into estrus until the child is eating solids. Only during estrus do the boys find the ladies attractive.
Now in her 40’s Nkombo has been coming into estrus for 6 days every month since she reached sexual maturity at the age of 12. Where as the other ladies in the community spend only a fraction of their life in estrus poor Nkombo gets hassled by the guys every month. Over the years she has formed a very close relationship with Kalunde ‘the king maker’ who is the oldest and most respected male. They are never far apart and on more than one occasion we have watched Kalunde protecting his girl friend from the advances of the other males.