Prairie dogs talk some pretty colourful talk. Not only do their alarm calls tell others about the type and size of approaching predators, but it seems they can also warn of the hue of an imminent threat.
Gunnison's prairie dogs are burrowing rodents that live in the grasslands of North America. Con Slobodchikoff of Northern Arizona University in Flagstaff and his colleagues had previously shown that they produce different alarm calls in response to humans, coyotes, domestic dogs and red-tailed hawks. For humans, the calls even vary according to the person's size. They react differently towards each call, all hiding if approached by humans, whereas only nearby animals hide if it is a hawk.In the latest study, the team recorded the alarm calls as three similar-sized women wearing blue, yellow or green T-shirts walked past the prairie dogs 99 times. They found that the calls were similar for green and yellow T-shirts, but significantly different for blue.
Prairie dogs have dichromatic vision, a form of colour blindness where only two of the three primary colours can be discerned. As they are sensitive to blue and yellow, this explains why they cannot distinguish green. Still, the fact that they can "talk" colour "probably makes this the most sophisticated animal communication system that has been decoded so far," says Slobodchikoff.