Survivor Signals: The Biology and Psychology of Animal Alarm Calling

Many social species produce specific vocalizations when threatened or startled by a predator or some other significant disturbance. These signals are usually termed ‘‘alarm calls’’ (from old Italian ‘‘all’ arme’’ meaning ‘‘to arms’’ on the approach of an enemy), but ‘‘distress,’’ ‘‘alert,’’ or ‘‘mobbing calls’’ are also common, usually in cases where the calls are given in conjunction with some specific antipredator behavior. Although many authors treatmobbing calls as functionally distinct from alarm calls, this distinction is not always useful. For example, many forest primates produce acoustically distinct alarm calls to ground predators, such as leopards, but these calls are often accompanied by mobbing behavior (e.g., Zuberbühler et al., 1997). In this chapter, I will therefore treatmobbing calls as a subtype of alarm calls, one that is linked with relatively specific antipredator behavior. Alarm calls have long been of interest to researchers and they have continued to bewilder and fascinate, for a number of reasons. A first one is merely practical. When working with free-ranging animals, it is often difficult to divide the continuous stream of behavior into discrete and meaningful units that can be studied systematically. Alarm calls are a rare exception. They are structurally and perceptually unique, which facilitates identification and systematic study considerably. Second, alarm calls are a particularly useful tool for studying cognitive mechanisms, often providing a rare window into an animal’s mind. Diurnal life and sociality are strongly associated with whether or not a species produces alarm calls (Shelley and Blumstein, 2005) and individual callers often require a specific audience (Zuberbühler, 2008). Because of these social dimensions, alarm calls are interesting for a number of scientific