DG: The rattlesnakes were a lucky break. You put them in a sandbox, and they just start sidewinding—the sideways slithering they do to cross sand. But most animals don't do what you want. Ghost crabs, for example, are ridiculously fast. In the laboratory, you can get about 10 good trials out of them: They'll run away from you down a track, where high-speed cameras record them. After that, they seem to decide they are no longer afraid and start trying to pinch you.