Last Wednesday BBC2’s Natural World documentary series had an intriguing programme called “Prairie dogs, talk of the town,” dedicated to the communication of prairie dogs. Prairie dogs are not dogs, but rodents. They belong to the squirrel family and live in prairies and grasslands of Arizona, New Mexico and Colorado. Praire dogs live together in large groups or colonies, building praire dog “towns”, vast networks of intertwined underground burrows.
Professor Con Slobodchikoff, a biologist from the Northern Arizona University has been studying their vocal communication for the past thirty years. Up to now it hadn’t been thought that rodent species would have a complex communication. The work of Slobodchikoff, however, shows that prairie dogs have particular alarm calls that refer to the different types of predators that hunt them. Three major types of alarm calls have been identified: a call for coyotes, one for badgers and one for hawks. When one of the prairie dogs gives an alarm chirp, the rest of the group of prairie dogs (the audience) will give an appropriate escape reaction. If a coyote alarm call is heard, the prairie dogs react by running to their burrows and sit up, watching the coyote from the edge of their burrow. However, when they hear a badger call they also run to their burrows but crouch down so the badger may not notice them.
It has been known that certain primate species, in particular the vervet monkeys of subSaharan Africa similarly have about three different alarm calls for the three types of predators that hunt them most (leopards, eagles and snakes). The prairie dog alarm calls function in a quite similar way and thus show that rodents are also able to differentiate between predators in the calls with which they warn their group members. In common with the primate species studied, the prairie dogs have to learn from experience how to use these calls and as they grow older their alarm calls get richer in meaning. Slobodchikoff recorded the prairie dogs’ alarm calls on tape and later played back the tape to various groups of prairie dogs. The prairie dogs gave the appropriate reaction to each alarm call, showing that these alarm signals function to refer to a particular type of predator.
Professor Slobochikoff even claims that prairie dogs are also able to express with an alarm call specific details about the particular predator, such as its general size, colour and speed of travel. For example, a single prairie dog bark could express “tall, skinny coyote in distance, moving rapidly towards colony.” This more specific information is uttered by the prairie dogs varying the modulation of the call and the harmonics within the bark. Slobodchikoff came to these conclusions by recording the alarm calls the prairie dogs gave to humans of various size and shape, wearing various colours of shirts. He found that the alarm calls had a different calling pattern in these different situations. However, when the humans wore a white laboratory coat that hid their specific features, the call was less informative. This claim that these alarm calls can give quite specific information about a predator is new in this area of research. Slobodchikoff has consequently come to the position that prairie dogs have a language that is only second in complexity to human language.
My own point of view is that the term ‘language’ refers to the characteristics of our human language. Language is built up of words or signs that function as symbols, carrying a particular meaning that refers to something in the outside world. Second, in human language these individual symbols are combined in a structured way in sentences, by which more can be expressed than through single words or signs. Furthermore, human language is not just used to express one particular communicative goal, but it has a large variety of functions, ranging from asking for attention to communicating about ideas and fantasies. Though it is often common practice to refer to the communication systems of nonhuman animals as language (e.g., the language of honeybees), the use of this term can lead to the mistaken assumption that the particular animals have all these fundamental characteristics of human language.
With the alarm calls of prairie dogs, though fascinating as they rightfully are, I prefer to keep using the word ‘communication’ rather than ‘language’ to describe them. This is because the alarm calls refer to predators only, the calls are not combined in a structured way and the function of these calls are limited to one context: when there is a threat of a predator entering their territory the calls warn the group members. Even when Slobodchikoffs claims are right that the alarm calls also give information about the size, colour and shape of the predator, the calls are still quite limited in comparison with human language.
It is very important, though, that we keep investigating the communication systems of the animals with which we inhabit our vulnerable world. Science is always continuing to develop and as pioneering researchers such as Slobodchikoff take on research projects to study the unknown communication system of prairie dogs, our knowledge will grow and so will our conclusions change on communication and language in animals.
It was very fascinating to watch the BBC documentary and see how these wonderful creatures live and communicate with each other. What I loved most was to see the reaction of the prairie dogs when a predator had left their territory and was no longer a threat. They would give a yip while jumping into the air, throwing their head back and raising their forelegs. The cry sounded as a sort of joyful relief or relaxation that the predator was gone. Slobodchikoff interprets these cries as a sort of “all clear” signal. This all-clear call is very infectious and when one priairie dog makes it, the others follow. This was delightful to watch.
On YouTube I found two videos that are of relevance here. The first video gives a nice introduction to prairie dogs:
And check out this video to hear the delightful jump-yip:
– Anderson, S. R. (2004). Doctor Dolittle’s Delusion. Animals and the Uniqueness of Human Language. New Haven: Yale University Press.
– Slobodchikoff, C. N., Kiriazis, J., Fischer, C. & Creef, E. (1991). Semantic information distinguishing individual predators in the alarm calls of Gunnison’s prairie dogs. Animal Behaviour, 42, 713-719.