The leap of a frog is a quintessential evolutionary feat. The critter’s girthy gams thrust from behind to springboard the body up and out; a pair of acrobatic arms stretch forward to seamlessly break the fall. The landing is “very precise, very controlled,” says Richard Essner, a biologist at Southern Illinois University Edwardsville. One might expect that any frog worth its salt should be able to stick it. “And most frogs,” says Marcio Pie, a biologist at Edge Hill University, in the United Kingdom, “do.” Then there is the poor pumpkin toadlet. Spanning roughly a centimeter from snout to bum—about...