Small Mammals and Ground-Dwelling Invertebrates Associated with Active and Controlled Colonies of Black-Tailed Prairie Dogs (Cynomys Ludovicianus) (Report‪)‬

Prairie dogs (Cynomys) once inhabited North American prairies from southern Canada to north-central Mexico, and from the eastern Rocky Mountains to the tall-grass prairies of the Great Plains (Hall, 1981). They were among the most numerous grassland herbivores and had a significant impact on nutrient cycling, plant succession, and biodiversity in the prairie ecosystem (Coppock et al., 1983; Archer et al., 1987; Weltzin et al., 1997). Over the past century, the extent of populations of prairie dogs has decreased by [less than or equal to]98% (Miller and Ceballos, 1994). In Texas, the range of the black-tailed prairie dog was estimated to have declined from ca. 330,000,000 ha in 1905 to ca. 37,500 ha in 1977 (Cheatam, 1977). The decline in abundance and distribution was principally the result of eradication programs, introduction of sylvatic plague, unregulated shooting, and habitat loss (Van Putten and Miller, 1999). As a result of these declines, the status of the black-tailed prairie dog was evaluated recently by the United States Fish and Wildlife Service, and a multi-state conservation strategy for the species was developed (United States Fish and Wildlife Service, http://mountainprairie.fws.gov/species/mammals/btprairiedog). Despite conservation concerns, use of toxicants to control prairie dogs remains a common practice. Previous studies have examined the impact of zinc phosphide and strychnine (common rodenticides used to control populations of prairie dogs) on non-target species (Deisch et al., 1989, 1990; Apa et al., 1991). These toxicants are applied with baits, commonly oats, which allow non-target species to ingest the rodenticides. Aluminum phosphide, a fumigant for burrows, commonly known as Phostoxin[R] (Degeshe Company, Inc., Weyers Cave, Virginia), is now being used as a method to control prairie dogs (Moline and Demarais, 1987). Tablets placed in burrows release hydrogen-phosphide gas that acts as a toxic fumigant, suffocating inhabitants. Phostoxin[R] was ca. 95% effective in controlling black-tailed prairie dogs (Salmon et al., 1982), and almost 100% effective in controlling ground squirrels (Spermoryhilus; Moline and Demarais, 1987). In addition to causing direct mortality to prairie dogs and other occupants of burrows, Phostoxin[R] may indirectly affect non-target species as treated burrows are closed and remain inaccessible for shelter and other uses. Nontarget species also may be impacted by changes to the local vegetative community that may result from elimination of prairie dogs from an area (Matt and Hein, 1978; Cid et al., 1991).