From The Times:

July 20, 2007
Baboons bear fruit of birth control
Nigel Hawkes

GASHAKA-GUMTI Baboons in the rainforests of Nigeria have found their own contraceptive pill – the African black plum.

Research by James Higham, of Roehampton University, and colleagues has found that the plum is a source of progestogen, and that eating it stops the female olive baboons' reproductive cycles. It also prevented the red swelling that female baboons produce when they are receptive to males.

Dr Higham, who published the study in Hormones and Behaviour, said that it was difficult to know if the behaviour was deliberate.