The Call That Contains a Description
In 1980, animal behaviourist Con Slobodikoff began recording the alarm calls of Gunnison's prairie dogs at a field site in Arizona. What he expected to find was a simple warning system, something like the vervet monkey's three-call repertoire, which distinguishes eagles from snakes from leopards. What he found instead was a language.Using computer analysis to break down the acoustic structure of prairie dog calls, Slobodikoff and his colleagues at Northern Arizona University identified that the calls were not just categorically different for different predators. They were compositionally different. The calls encoded specific physical descriptions of individual threats: the height of an approaching human, the colour of their shirt, whether they were carrying an object, how fast they were moving. In one controlled experiment, four humans in differently coloured shirts walked through a prairie dog colony on separate passes. The colony produced acoustically distinct calls for each person, calls that, when decoded, corresponded to the shirt colour and the person's size. The prairie dogs were not just saying "danger." They were saying what kind.
