Crows Hold Grudges for Years and Warn Others

Crows never forget people who wronged them. Moreover, they share this information with other crows. In an experiment at University of Washington, researchers wearing masks disturbed crows. Years later, anyone wearing that mask - even strangers - was attacked by crows. Crows had taught this "enemy face" to their offspring and friends. Even crows who never witnessed the original event gave warning calls. Cultural transmission isn"t unique to humans. Source: Animal Cognition Journal