Batesian mimicry occurs when a non-toxic or harmless organism looks highly similar to an organism that is toxic or venomous. An example is the viceroy butterfly which is harmless, but looks extremely similar to the monarch butterfly, which is toxic and bad-tasting when eaten. As a result of the similarity, the harmless organism may be avoided by predators. Bright colors are often advertisements for toxicity, to alert predators to avoid the animal.
Another familiar example are coral and king snakes. Coral snakes have highly toxic venom, but king snakes are harmless. A common means for distinguishing the two is, "red touches yellow, you're a dead fellow. Red touches black, you're okay, Jack." But is the similarity as useful in the extreme reaches of the snakes' range? If king snakes live in areas where predators have little or no exposure to coral snakes, they are actually in danger, as their bright colors make them more apparent to predators. Researchers investigated the predation rates on king snakes at varying distances from the boundary of coral snakes' range, to determine whether there was an effect.