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Now even this final boundary is being challenged. Con Slobodchikoff at Northern Arizona University has done some of the most amazing studies in animal communication and cognition. Using sonograms to analyze the distress calls of Gunnison's prairie dog, one of five species of prairie dogs found in the U.S. and Mexico, he has found that prairie dog colonies have a communication system that includes nouns, verbs, and adjectives. They can tell one another what kind of predator is approaching -- man, hawk, coyote, dog (noun) -- and they can tell each other how fast it's moving (verb). They can say whether a human is carrying a gun or not.
They can also identify individual coyotes and tell one another which one is coming. They can tell the other prairie dogs that the approaching coyote is the one who likes to walk straight through the colony and then suddenly lunge at a prairie dog who's gotten too far away from the entrance to his burrow, or the one who likes to lie patiently by the side of a hole for an hour and wait for his dinner to appear. If the prairie dogs are signaling the approach of a person, they can tell one another something -- about what color clothing the person is wearing, as well as something about his size and shape (adjectives). They also have a lot of other calls that have not been deciphered.
Dr. Slobodchikoff was able to interpret the calls by videotaping everything, analyzing the sound spectrum, and then watching the video to see what the prairie dog making a distress call was reacting to when he made it. He also watched to see how the other prairie dogs responded. That was an important clue, because he found that the prairie dogs reacted differently to different warnings. If the warning was about a hawk making a dive, all the prairie dogs raced to their burrows and vanished down into holes. But if the hawk was circling overhead, the prairie dogs stopped foraging, stood up in an alert posture, and waited to see what happened next. If the call warned about a human, the prairie dogs all ran for their burrows no matter how fast the human was coming.
Dr. Slobodchikoff also found evidence that prairie dogs aren't born knowing the calls, the way a baby is born knowing how to cry. They have to learn them. He bases this on the fact that the different prairie dog colonies around Flagstaff all have different dialects. Since genetically these animals are almost identical, Dr. Slobodchikoff argues that genetic differences can't explain the differences in the calls. That means the calls have been created by the individual colonies and passed on from one generation to the next.
Is this "real" language? A philosopher of language might say no, but the case against animal language is getting weaker. Different linguists have somewhat different definitions of language, but everyone agrees that language has to have meaning, productivity (you can use the same words to make an infinite number of now communications), and displacement (you can use language to talk about things that aren't present).
Prairie dogs use their language to refer to real dangers in the real world, so it definitely has meaning.
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