Y: Look, Don, there’s an orangutan up there!

D: Where?

Y: It just climbed up to where we can’t see him. You think it’s off to tell all its friends about the annoying humans it saw?

D: Probably not in so much detail—but researchers do think they’re able to communicate about past events. Orangutans make a “kiss-squeak” noise when they see a predator to warn each other of danger. Nothing unusual about that—lots of animals have alarm calls. But now researchers have heard orangutans make the noise after the danger has passed—a sign that they’re communicating about the past, and the first evidence that primates other than humans have that ability. Researchers set up an experiment in Sumatra’s Ketambe forest in which a scientist draped in a striped, spotted, or plain sheet walked on all fours under trees where female orangutans were sitting. They expected the orangutans to sound their kiss-squeak alarm right away, but they didn’t. Instead, they quietly grabbed their infants and slowly climbed higher up the tree. The orangutans waited an average of seven minutes before making the noise, and one even waited twenty minutes.

Y: And the orangutans weren’t just too paralyzed with fear to make the noise right away?

D: Probably not, since they were able to grab their infants and climb. Researchers think the female orangutans were being quiet so they wouldn’t attract attention, and made the noise afterwards to let their infants know about the danger they were just in.

Y: Sounds like something a human mother would do—apart from the climbing up a tree part.