Curiously, females are known to sync up their menstrual cycles—and how fertile they are—in a number of primate species. Humans may synchronize menstrual cycles as well, although this remains controversial. Whether or not chimpanzees, the closest relatives of humans, sync up their menstrual cycles had been uncertain.
To shed light on this phenomenon, primatologist Akiko Matsumoto-Oda at Okinawa University and her colleagues investigated wild chimpanzees (Pan troglodytes schweinfurthii) at Mahale Mountains National Park in Tanzania by the shores of Lake Tanganyika. There, Japanese researchers have studied the chimpanzees for more than 40 years.
After analyzing nine years of data, the team found chimps actually avoided synchronizing their fertility. The findings are detailed in the March issue of the journal Behavioral Ecology and Sociobiology.