Black-tailed prairie dogs exhibit a high degree of social organisation, living in enormous colonies known as ‘towns’ containing from hundreds to millions of individuals (1) (7). Each colony shares an elaborate network of burrows for shelter and protection against predators, often covering areas of 100 hectares or more (1), with the largest ever recorded colony covering 65,000 square kilometres and containing an estimated 400 million animals (1) (7)! Colonies are subdivided into ‘wards’, and then into smaller family units called ‘coteries’, populated by a group of closely related females, one or two territorial males, and any offspring under two years of age (7) (8). Members of a coterie share food supplies outside of the breeding season and cooperate to aggressively defend their territory from neighbours (2) (7). However, while males respond strongly to intrusion by other males they seem oblivious to invading females; females, by contrast, show the most hostility toward invading females. During the breeding season, females aggressively defend their natal burrow against other females and, given the opportunity, will even raid the burrows of other females and kill their pups (7).
Mating is polygynous, with the usually single male mating with multiple females within his coterie. In cases when there is more than one resident male, usually brothers, females will mate with both. Reproduction occurs once per year in spring, although the timing varies with latitude, and females are typically sexually receptive for only one day of the year (7). A litter of one to eight pups is born after a gestation of 33 to 38 days. Young are born blind, naked and mostly helpless (7), and do not emerge from the burrow until around six weeks of age, and are weaned shortly after that (4). Interestingly, after emerging from the burrow, but prior to the end of lactation, pups may nurse from females other than their own mother, an example of ‘cooperative breeding’ (7). Females remain in their natal coterie for life, while males disperse before their first breeding season (7) (8). Likewise, adult males rarely remain within the same coterie for more than two breeding seasons, probably to reduce the possibility that they will mate with their own female offspring. Females can live up to eight years of age, whereas males tend not to live longer than five years in the wild (7).
The black-tailed prairie dog is diurnal and active throughout the year (7). Unlike many other species of prairie dog, these animals do not hibernate, although when the winter weather is extremely cold or snowy they may spend extended periods of time underground (2). Most activity is conducted during the cool hours of the day, when individuals engage in social activities, such as grooming each other, as well as feeding on grasses, herbs and the occasional invertebrate (7), while midday hours are usually spent sleeping below ground (4). Most prairie dogs forage close to their burrows when possible, moving into distant foraging areas only when forced to do so by local shortages of green shoots (7). While prairie dogs are out foraging, a sentry perches on the volcano-like ring that surrounds the burrow and watches for predators. Should a predator or any other danger be spotted, the sentry will bark out a warning, causing the community to dive into their burrows and wait for the ‘all clear’ call before venturing out again (7).