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The Conversation: Otters, beavers and other semiaquatic mammals keep clean underwater, thanks to their flexible fur

photo of Andrew DickersonUnderwater 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.

Assistant Professor of Mechanical Engineering Andrew Dickerson and his team recently published a study showing that fur that was allowed to move back and forth in a flow of dirty water accumulated less than half the amount of dirt as fur that was held stiff from both ends.

While lots of animals have fur that seems to clean itself, semiaquatic mammals have the most grime-resistant, or “anti-fouling,” fur.

The recent study compared fur fibers from beavers, otters, springbok, coyotes and more using a flow of water containing titanium dioxide, a common additive in cosmetics. Titanium dioxide readily attaches to surfaces like skin. The team pumped the dirty water over individual fibers in a closed loop for 24 hours, then cleaned the fibers to measure how much titanium dioxide they’d accumulated.

Dickerson and his colleagues then used mathematical techniques to combine all of the fur’s properties into a single number that predicts its anti-fouling behavior. They considered each fur strand’s ability to bend, how fluid flows over it and other unique features of each species.

They found that the ability to flex was critical for keeping the animal’s fur clean. Read the full article on The Conversation.