LISLE, ILLINOIS--It's not quite a candlelight dinner, but a shared meal of monkey meat was long thought to be a prelude for sex among chimpanzees. Now, new research shows that male chimps don't share their food to get females in the mood--they just want them to stop grabbing their meal, according to a study presented here today at an international ape research meeting.
Most animals don't share their food with unrelated individuals. But chimpanzees are an exception: After a male chimp kills his prey, he will often share the meat with unrelated chimps that come by to beg. Because male chimps step up hunting at the same time females in their troop come into estrus, researchers proposed in the 1970s that male chimps exchanged meat for sex with fertile females. To test that idea, animal behavior specialist Ian Gilby of the University of Minnesota, Twin Cities, spent 3 months in Gombe National Park in Tanzania watching how--and if--an alpha male named Frodo shared his meals with one of eight nearby females.
After Frodo captured and killed his favorite food, 30-centimeter-long red colobus monkeys, Gilby noted whether he shared meat with females that sat next to him and begged. In 29 meat-sharing interactions, Frodo was equally likely to share his food whether or not a female was in estrus and ready to have sex. What's more, he shared his food readily all 16 times a hungry female tried to grab his food, but kept it to himself 9 of 13 occasions when less aggressive females came by and stared balefully at his snack. The results suggest that rather than share meat for sex, the chimps dole out helpings because fighting for it wastes too much time and energy, says Gilby.
Gilby's work gets a thumbs-up from other experts. "He's focusing on an easy explanation and he's probably right," says primatologist Janette Wallis of the University of Oklahoma Health Science Center. Still, the chimps could be sharing now to receive rewards like social support or sex later on, she says--a rationale she likens to bringing a box of chocolates on your first date.