Aye-ayes are lemurs, or primates native to Madagascar, an island east of Africa. They have five long fingers on each hand. The middle and ring fingers are extra long. They use the middle finger to fish out bugs from under tree bark. Recently, scientists discovered another use—picking boogers and eating them!

Biologist Anne-Claire Fabre noticed Kali, an aye-aye in captivity, sticking her long finger into her nose. Then Kali licked the snot that came out! “I was really surprised,” says Fabre. To figure out where the finger went, she studied 3-D models of an aye-aye’s skull created using a machine called a CT scanner. It’s possible Kali’s finger reached her mouth and throat!

Fabre realized that many other primates with high dexterity—skill at using their hands and fingers—are also snot eaters. This includes chimps, gorillas, and humans! But why eating snot is so common remains a mystery.