Prairie dogs are divided into two general classes, the blacktailed and the whitetailed. Blacktails inhabit the semi-arid regions of the Great Plains; whitetails live in the higher elevations of mountain parks and foothills. But it’s difficult to generalize, for Devils Tower and Wind Cave National Park, in South Dakota, are in the Black Hills and the prairie dogs at both are blacktails. The dog town at Devils Tower occupies a level grassland bench between the Tower’s base and the nearby meandering Belle Fourche River. Blacktails are protected in their more typical arid topography at two other National Park System areas: Badlands National Park in South Dakota and Theodore Roosevelt National Park in North Dakota. Generally, as a result of dissimilar habitats, the two species exhibit slightly different patterns of behavior. Unlike the blacktails, which emerge to forage on sunny winter days, whitetails are confined to their burrows by deep mountain snows. Those at high elevations must hibernate to survive the long winter. The whitetail community is a much less highly developed social structure than the blacktail community. The animals are unable to enjoy the luxury of long summers. In the short season they must spend a great amount of time feeding to store up body fat for winter. They have little time for social rituals—grooming, greeting, or play. Time does not allow them to establish and maintain territories. The burrow is to the prairie dog what speed and endurance is to the pronghorn: its chief means of protection. Yet it is more than just a hole in the ground, a temporary refuge from the threat of danger. More than half of a prairie dog’s life is spent below ground, so the burrow must accommodate a wide range of needs (See pages 56-57.). Often old burrow systems are abandoned and new tunnels excavated. The debris from the new tunnel system is dumped into the old burrows. These plugged burrows, called cores, may, in time, be more extensive than active tunnels in a long-occupied town. Whether knowingly or unknowingly, the prairie dog, by plugging unused passages, is practicing sound engineering; if all excavated material were brought to the surface, the weakened sub-surface, riddled with tunnels, would begin to settle and the burrows would eventually collapse.