Observations on the Biology of Gunnison's Prairie Dog in Central Colorado

Abstract

A study was conducted from July 1965 to September 1966 on the biology of Gunnison's prairie dog (Cynomys gunnisoni gun- nisoni) in South Park, Park Co., Colorado. Prairie dogs within the colony were loosely organized into clans with adult females playing the major role in caring for the young and! warning of danger. Clan bound- aries were not patrolled or defended by clan members, but individual burrows, burrow systems or food supplies were protected by individual animals. Little aggression was observed within the clans but members of different clans would engage in disputes when they encountered each other in the common feeding areas. Females had a high ratio of suc- cessful pregnancies or uterine implantation sites, but mortality caused by a plague (Yersinia pestis) epizootic resulted in the extinction of the main study colony by the spring of 1967. Mean weights of adult males were significantly higher than weights of adult females. Weights of pups in- creased during the first summer so that by September a few individuals were as large as smaller adults. Immigration and emigration were not important in the colony and the only known successful predators were badgers and red-tailed hawks. Tactile, visual and vocal communication was important in the colony, but in general social behavior was not as well developed as in black-tailed prairie dogs. Prairie dogs were diur- nal with two periods of maximum surface activity. Gunnison's prairie dogs completely terminated surface activity for 7 months during the cold seasons of the year, with pups being the last animals to hibernate. Gun- nison's prairie dogs did not work or shape their mounds and their activ- ity had little visible impact on their environment. Most of the time the animals spent aboveground was occupied in eating or searching for food. Grasses were the preferred foods but a variety of forbs were also utilized.