A vocal alarm response, common amongst birds and mammals. They often include auditory signals that make it difficult for a predator to locate the calling animal. To be difficult to locate, a sound should begin and end gradually, so that the predator cannot easily compare the times at which the sound reaches the two ears. For the same reason, it should be uniform in pitch. Low-pitched sounds are generally harder to locate than high-pitched sounds, and the alarm calls of many small birds are typically low-pitched, continuous calls, which begin and end gradually. In fact, these calls are so similar to each other that they often serve to warn members of more than one species. Some species, e.g. vervet monkeys (Cercopithecus aethiops) and chickens (Gallus gallus domesticus) have different alarm calls for different types of predator.
Subjects: Evolutionary Biology — Zoology and Animal Sciences.