Poison dart frogs opt for gaudy warnings of their toxicity, rather than the green or mottled skin of other frogs. They're committed to their position as evolutionary standouts: The loud colors, which keep predators away, in turn allow the frogs to have a more boisterous mating call. "These noisy kinds of calls, in general, are what the females really like," states Juan C. Santos, a zoologist and part of a team who recently discovered brighter frogs have the loudest sounds.
2. American Alligator: 90 Decibels