Why otters ‘juggle’ rocks is still a mystery

A lovely, intuitive idea about why otters juggle rocks — that it helps them practice survival skills — might not be correct, new tests show.

The term “juggling” is itself overenthusiastic. Otters don’t keep stones flying around in some tall, aerial circle. Instead, the animals shuffle rocks back and forth quickly between their front paws. “It’s very close to the body,” says animal behaviorist Mari-Lisa Allison, who studied the behavior as a graduate student at the University of Exeter in England.