Iris patterns offer a noninvasive way to recognize individual Amazonian treefrogs‎

Identifying individual animals in the wild has long meant tagging, branding or clipping. For amphibians, the standard approach has often been toe-clipping, a procedure that can affect survival, physiology and behavior. A new study suggests that, for at least one species of treefrog, nature has already provided a more humane solution: the eyes.