For animals that are hunted, a “prey communication device” is an evolved biological feature or behavior. These adaptations are used to send and receive information about the presence and nature of a threat. This system of signals is a product of evolution, where the ability to convey a message can mean the difference between life and death. The messages can be directed at the hunter, members of their own species, or sometimes both.
Pursuit-Deterrent and Warning Signals
Prey animals communicate directly with predators to persuade them that an attack would be a waste of time and energy. One of the most visible examples is aposematism, or warning coloration. Animals like poison dart frogs, with their vibrant skins, and monarch butterflies, with their distinct orange and black wings, are advertising their toxicity. Predators learn to associate these bright colors with an unpleasant or dangerous meal.
Another form of predator-directed communication involves signals of fitness. A gazelle, upon spotting a cheetah, may begin to stot—leaping high into the air with all four legs held stiff. This display is an honest signal of the gazelle’s physical health and agility, showing the cheetah it is strong enough to escape a chase. Similarly, a white-tailed deer will raise its tail, flashing the white underside, to signal to a predator that it has been seen and is ready to flee.
Alarm Calls and Cues
Prey animals also communicate among themselves to warn of danger. The intended audience for these signals is not the predator, but rather relatives and other members of the social group. The alarm calls of prairie dogs, for instance, alert the entire colony to a threat, allowing others to quickly retreat to their burrows. This behavior, which can draw a predator’s attention to the caller, is often driven by kin selection, as the caller is protecting its genetic relatives.
In aquatic environments, chemical cues are a common method of alarm. When a schooling fish like a minnow is injured by a predator, its skin can release a chemical substance. This pheromone, known as Schreckstoff (a German word for “fright substance”), dissolves in the water and is detected by nearby fish. The chemical signals an active threat, causing other minnows to engage in defensive maneuvers, such as schooling more tightly or fleeing the area.
Information Encoded in Signals
Prey signals are often more complex than a simple alert, encoding specific details about the threat. This allows for a more tailored and effective response from the group. The information can specify the type of predator, its location, or the immediacy of the danger.
Vervet monkeys in Africa are a classic example. They have developed distinct alarm calls for different types of predators. A specific “bark” is used to warn of a leopard, prompting other monkeys to climb high into the trees. A “cough” sound signals an eagle, causing the monkeys to look up and seek cover in dense bushes. A “chuttering” call is used for snakes, leading the group to stand on their hind legs and scan the ground.
The intensity or repetition rate of a call can also convey the level of risk. An animal will call more frequently or loudly when a predator is very close compared to when it is farther away. This allows the recipients of the signal to gauge the urgency of the situation and react appropriately.