Through recording the calls prairie dogs made in response to predators?a hawk or human or coyote, for example?and then analyzing the call?s layers of frequencies in a computer lab, Slobodchikoff discovered that the calls were grouped together into frequency clusters, with obvious differences between a general warning call or an alarm about a domestic dog versus a coyote.
This in itself spurred more inquiry?why is the prairie dog call for “human!” consistently different than the others, and is there a possibility that prairie dogs are distinguishing between different humans?
“He began to wonder whether the little rodents could possibly be describing their predators ? not just differentiating hawk from human, but actually saying something about the particular human or coyote or hawk that was approaching.”
His test for this was quite simple, actually. He dressed four humans in four different colored shirts?blue, yellow, green, grey?and had them walk through the prairie dog village four times. After recording the warning calls and then analyzing them, Slobodchikoff found that the calls organized themselves based on the color of the human?s shirt. Amazingly enough, the calls even differentiated between other factors like height?”?Essentially they were saying, ?Here comes the tall human in the blue,? versus, ?Here comes the short human in the yellow.?”
It seems as though every time we study animal communication, the more we are discovering their intelligence and perceptiveness. I don’t know of any reason to think that groundhogs are uniquely capable of this sort of “language” whereas other rodents and species are not. If we haven’t noticed the complexity of animal communication before, it’s quite likely because few people were looking (Francis of Assisi, patron saint of animals, aside).