Sex in exchange for fruit
The way to a mans heart is through his stomach. With monkeys, this also seems to apply to females. Researchers from the Scottish Stirling University discovered that male chimpanzees steal fruit from gardens and fields to impress their lovers.
With the raids, the males show their bravery to the other members of the group, especially to the females. The gifts (the stolen fruit) made the females more prepared to have sex. Observations of a group of chimpanzees showed that the monkeys that shared their fruit with the females, had even more sexual contact than the alpha male (which is the most important male of the group).
For this research, the scientists observed a group of chimps in the west of Africa for two years.