The actions that animals take to give information are called signals or displays. There are five types of signals or displays: sound or vibration, visual, chemical, touching, and electric. Often, the most effective way for an animal to give information is by a sound display. Sound spreads rapidly, and other animals in the vicinity can readily tell from what direction it comes. The most common sounds are vocalizations made by vertebrates (animals with segmented spinal columns), such as birds, reptiles, and mammals. A small bird may vocalize a sound of fear in the presence of a predator such as a hawk or a cat, thus warning other small birds in the area to flee. There are also nonvocal sounds. Some insects rub one body part against another, an act called stridulation. Beavers and gorillas, though they can vocalize, also use vibration sounds. To warn others of danger, beavers slap their tails on the water surface and gorillas beat their chests.
Visual communication can be conducted through the use of such badges as a patch of bright color or a set of horns. These badges give some indication