Can animals talk? Once the answer would have been a simple no: although animals may communicate by issuing a bark, shriek, or moo, those vocalizations--to use the animal behaviorists’ careful distinction--were assumed to have no specific internal meaning. The difference between vocalizing and talking is the difference between crying Oh! when you see an ax murderer in your house, and crying Look out, dear, there’s an ax murderer in the house! Animals, it was thought, could do only the former; only humans could do the latter.
The trend lately has been away from this particular bit of human arrogance and toward the view that our linguistic abilities, while unique, lie at the top of a continuum that extends well into the animal kingdom. Constantine Slobodchikoff, a biologist at the University of Northern Arizona, is at the leading edge of that trend. In five years of field studies he has mapped out what he calls a very sophisticated abstract communication system--not in chimpanzees, nor in dolphins, but in prairie dogs. It seems the little rodents do more than shout Oh! when a murderer is about.
Prairie dogs live in flatland colonies across the American West, munching on grass while scampering between burrows. To warn each other of hawks, coyotes, humans, and other predators, the dogs emit high-pitched staccato barks, often while stationed at the edge of their burrows, ready to dive for cover. Early in his study of prairie dog colonies near Flagstaff, Slobodchikoff began to suspect that the animals might have different alarm cries for aerial and terrestrial predators; other researchers had found similar traits in chickens and ground squirrels.
Slobodchikoff’s hunch proved accurate. But that wasn’t the whole story, he says. The barks actually seemed to vary between terrestrial predators. At first Slobodchikoff thought the apparent variations were just chance--that the prairie dogs he’d recorded responding to, say, a coyote were different individuals from the ones he had recorded barking at a human. We thought each prairie dog might have an individual voice, he says. But then we took a single domestic dog and a single human, walked them through colonies, and recorded the calls. The variation for each went down to almost nothing. The human-triggered alarms sounded the same from prairie dog to prairie dog--but very different from the calls that warned of Rover.
More impressive still, Slobodchikoff has found, is that prairie dogs discriminate among individual humans--or at least among the members of his research team, who walked individually through a colony--of different height, weight, and clothing. All these distinctions are apparent not in the number or length of the barks but in their tonal qualities. For instance, the pitch may rise and fall more rapidly in response to one human than it does in response to another.
It seems, then, that instead of just announcing danger (Oh!), the prairie dogs tell one another something about it (It’s that murderer in the hideous plaid!). This makes sense: Since prairie dogs seldom venture far from their colonies, they may be harassed by the same enemy time and again. And since individual predators may have characteristic hunting tactics, it would be to the prairie dogs’ advantage to distinguish among them.
Certainly they respond differently to different alarms. Last summer Slobodchikoff and his colleague Judith Kiriazis put loudspeakers near a colony and played back various warning cries. Though lacking visual signs of a predator, the prairie dogs nonetheless searched the skies for nonexistent hawks, dove for cover from invisible coyotes, and so on. Slobodchikoff still has to show that the animals respond differently to different individual predators (real ones, not biologists)--that’s next on his agenda.
His work so far has evoked barks of surprise from his peers. There’s been tremendous interest, he says, but also tremendous skepticism. Many people didn’t believe this was possible. It doesn’t really fit the accepted paradigm of what animals are capable of doing.
But Slobodchikoff thinks his prairie dogs may be capable of even more. An approaching predator, after all, is a subject that offers limited scope for conversation. Slobodchikoff plans to examine the prairie dogs’ chatter during foraging, when they might be expected to engage in more complex exchanges. It’ll be like a man from Mars coming down and listening to a cocktail party, he says.