Sheep, giant pandas, mouse lemurs, capybaras, and fur seals all have something in common when it comes to communication. All of them produce calls with rapid, vibrato-like fundamental frequency modulation—commonly known as bleats or trills. Now, researchers reporting in Current Biology on August 24 think they know why that call feature has arisen multiple times over the course of evolution: it improves the ability of listeners to detect call components that provide important identifying information about a caller.