Each time chimpanzees watch someone else soak up water with a mat of vegetation, they're 15 times more likely to use their own sponges later, the team of Canadian and European researchers estimate. They were alerted to the trend after observing a 29-year-old alpha male chimpanzee, named Nick, who crafted a sponge out of moss. Nick, in turn, was being watched by Nambi, a female chimp, who spread the behavior to a total of seven apes in Uganda's Sonso chimpanzee community over the next week.
Primatologists call leaf-sponging a "universal behavior," in which chimpanzees of all ages will drink water from leaves. It's a tool use that dates back decades. But this group of apes didn't develop the new sponging behaviors - reusing old sponges or mixing together leaves and moss - until November 2011, giving the researchers the chance to watch as the techniques spread from chimp to chimp.
(YouTube: PLOS Media)