Underwater surfaces can get grimy as they accumulate dirt, algae and bacteria, a process scientists call “fouling.” But furry mammals like beavers and otters that spend most of their lives wet manage to avoid getting their fur slimy. These anti-fouling abilities come, in part, from one of fur’s unique properties — that each hair can bend and flex as an animal moves. I’m a mechanical engineer who studies fluid dynamics, or how liquids behave. My team recently published a study showing that fur...