Recovery of black-tailed prairie dog colonies following a sylvatic plague epizootic
Fennell, Jeffry Dwight
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Black-tailed prairie dogs suffered a 94-99%' reduction in habitat during the twentieth century. In recent decades, the introduced pathogen responsible for sylvatic plague has led to local extirpation of prairie dog colonies, reduction in colony size, and increased isolation between surviving colonies. Consequently, plague has become the biggest challenge to prairie dog conservation. For this study I estimated prairie dog densities on the Northern Cheyenne Indian Reservation following a sylvatic plague epizootic in the 1990s. I estimated densities using mark-recapture techniques and visual counting methods. I compared variations in densities based upon a colony’s plague history and colony size. I hypothesized that densities would be higher on colonies that most recently experienced the plague. In 2000, prairie dog densities ranged between 11-91 prairie dogs/ha from 21 colonies. Densities ranged between 5-90 prairie dogs/ha from 23 colonies in 2001. Prairie dog density did not differ between years. There was no significant difference in densities based upon presence or absence of past plague or colony size. Colonies that had most recently recovered from a sylvatic plague had the highest densities. I also examined factors relating to a colony’s probability of having had the plague, such as nearest neighbor distances, habitat between nearest neighbor, and distance to nearest road. I predicted that colonies would be more likely to contract plague if distances between neighboring colonies were small, the habitat between colonies facilitated dispersal, or colonies were on or near migration corridors. The distances to the nearest plagued colony and nearest non-plagued colony were the best predictors of a colony’s probability of having experienced sylvatic plague. For those colonies that had sylvatic plague in the 1990s, distances to other colonies with plague were shorter (x = 3.1 km) than to colonies that did not experience plague (x = 19.7 km).