Prairie dogs: Organized social systems
Few, if any, predators are able to make a meal of a mole-rat. It can dig faster than any predator and it has no need to come to the surface. But those burrowers that do not eat grass blades must emerge from their holes and then become targets for predation. The plains of North America are colonized by rodents called prairie dogs or Marmots (e.g. Cynomys ludovicianus). They not only graze above ground but do so during the day when coyotes, bobcats, ferrets and hawks are about, all predators of the prairie dog. These animals have developed defences which depend upon a highly organized social system. They live in huge concentrations called towns which may contain up to a thousand animals. Each town is divided up into a number of communities called coteries of about thirty individuals, all of whom know one another well. Many have interconnecting burrows. The coteries always have some members on sentry duty, sitting upright on the mound of excavated earth beside the burrow entrance where they can get the best view of what is going on. If a potential predator is spotted the sentry lets out a series of whistling barks. Different kinds of predators elicit different calls so that the other prairie dogs know where the danger comes from. The call is repeated by others nearby and so spreads through the town, putting every-one on guard. The inhabitants do not immediately take to flight but take up strategic positions close to their holes. From there, standing on their hind legs, they stare at the intruder, watching its every move. So as a coyote trots through the town, the alarm spreads from coterie to coterie and the intruder is met with fixed glares from the citizens who let it come tantalisingly close before they duck into their burrows.