In his 11 years studying ant behavior, biologist Erik Frank had never seen anything like it. He and his colleagues at the University of Würzburg brought Florida carpenter ants back to their lab in Germany to learn how they respond to injury. Most ant species treat the injured or severed limb of a comrade by coating it with an antimicrobial goo. But the reddish-brown carpenter ants took a different tack: They bit the remainder of the limb off, effectively amputating it.

Other animals, such as lizards, shed their own limbs to escape predators, but Frank says this is the first case of an insect severing the leg of a nestmate to save its life. The only other species that does this is humans. “I didn’t believe this at all because it was very counterintuitive,” he says. “I repeated the experiment four times before I accepted it.”