In many corners of the animal kingdom, shells are a time-honored way of preventing predators from sinking their pointy parts into an animal's most sensitive bits. Sometimes, though, shells can hinder a creature's ability to defend itself. And new research has found some animals that put their shells to use in perhaps the least expected ways. The Best Defense is Episode 10 of Menagerie, a podcast about animals, their stories, and how we interact with them.