Underground Towns

WHERE are the world’s biggest towns? In the North American grasslands or prairies. And no, they are not inhabited by humans, but by a type of small ground squirrel known as the prairie dog. Prairie dogs are named for their shrill barking calls. They are furry brown burrowing rodents, around 30-50 cm in length and weighing about a kilogram. There are five species but the commonest are the black-tailed and the whitetailed prairie dogs. They are found throughout the continent, from Mexico in the south to Canada in the north. Prairie dogs are considered a menace by farmers and ranch-owners, who call them ‘prairie rats’. Farmers complain that the rodents destroy the grass needed for their livestock and that their animals break their legs when they step into the burrows. The massive network of 4.5-m deep burrows that prairie dogs construct under the ground is called a colony or a town. Prairie dog towns are immense — one found in 1901 covered an area measuring 380 km by 60 km and may have been home to 400 million individuals! One female may mate with as many as five males in the burrow. There are one to six babies, called pups, in a litter. Though they feed mainly on grass, female prairie dogs are known to kill and eat each other’s pups. Prairie dogs have a system of calls. They can distinguish between predators, making different sounds for humans, hawks, coyotes and dogs. They can even distinguish between people of different sizes and recognise someone they have not seen for two months!