A warning signal given by an animal to other members of its population in response to perceived danger, usually the approach of a predator. This is a form of altruism, since the animal that has perceived the danger may waste valuable time in giving the signal (or attract the attention of the predator by doing this) and thus reduce its own chances of survival. For example, the alarm signal of a rabbit to a threatening situation involves thumping the ground and then flashing the white of its tail as it runs, which alerts the rabbits nearby.