We don’t eat food off dirty floors. We dutifully wash our hands. We steer away from the clearly infected. It's all part of avoiding things likely to make us sick, and new research shows our primate cousins do it too.

Except the mandrill's method is a bit more unsavory: smelling each other's poop.

By detecting the odor of intestinal parasites in their group members' feces, these central African monkeys identify who is ill—and then avoid grooming them.

Grooming is important to mandrills: It soothes conflict and builds relationships, as well as keeps fur and skin free of pests. But this social behavior can also spread parasites, such as E. coli bacteria and other microbes that cause dysentery.

“We found that gastrointestinal parasites were