If a mimicry system offers protection from predators, then why hasn't evolution eliminated the "failed mimics," such as ground snakes sporting color patterns that don't remotely resemble a coral snake? That's the puzzle that University of Michigan evolutionary biologist Alison Davis Rabosky has spent the last four years trying to solve.

"Logic predicts that non-mimics should by eaten preferentially by predators and, given enough time, you should end up with a single color type in the population. So the widespread co-occurrence of mimic and non-mimic color patterns is a puzzling and longstanding evolutionary paradox," said Rabosky, an assistant research scientist in the Department of Ecology and Evolutionary Biology and an assistant curator of herpetology at the Museum of Zoology.

While Rabosky and colleague Christian L. Cox of the University of Virginia don't claim to have fully resolved the paradox, they did gain insights that help explain the persistence of non-mimic color patterns in ground snakes, especially rare patterns. It turns out that if you're a ground snake, displaying a rare color pattern also provides an evolutionary edge.