Black-Tailed Prairie Dog Food Habits and Forage Relationships in Western South Dakota

Abstract

Four plants made up 65% of items in fecal pellets of the blacktailed prairie dog in western South Dakota. These important forages in order of significance were sand dropseed, sun sedge, blue grama and wheatgrasses. Grasses made up 87% of the total diet, while forbs comprised 12%. Shrubs, arthropods, and seeds made up 1% or less of the diet. Preference indices were highest for ring muhly, green needlegrass, and sand dropseed. Relationships of diets to available forage was weak, having an average similarity of 25%; rank-order correlations were nonsignificant, indicating that black-tailed prairie dogs are selective feeders. Black-tailed prairie dogs (Cynomys ludovicianus) are common herbivores on western rangelands. Much attention, since the 1800's, has focused on forage competition between livestock and prairie dogs. Widespread control programs for prairie dogs were begun in the late 1800’s and early 1900’s on the Great Plains, when it was estimated that 256 prairie dogs would eat as much forage as 1 cow (Merriam 1902). The concern over livestock and prairie dog grazing competition still exists; large-scale control programs for prairie dogs are being conducted even with costs as high as $6/acre on land which generates grazing fees of $2.95/acre (Collins et al. 1984). Dietary information is essential t o assess the role of the prairie dog in prairie ecosystems. Since Kelso ( 1939) first presented general data on black-tailed prairie dog diets, research has been conducted in Colorado (Tileston and Lechleitner 1966, Bonham and Lerwick 1976, Hansen and Gold 1977); Montana (Fagerstone et al. 1977); and South Dakota (Summers and Linder 1978, Fagerstone et al. 198 1). Dietary information is presented in these studies; however, data on diet-forage relationships and preference indices are generally lacking. Most of these studies were conducted in National Parks or in areas with limited grazing by cattle. Dietary information by species will vary from region to region even though major categories consumed by prairie dogs (grasses, forbs, shrubs) are similar. Intensive management of our rangelands must be based on plant species consumed by herbivores in the area of interest. The purpose of this study was to estimate the diets of blacktailed prairie dogs as related to the availability of range vegetation on pastures grazed by cattle, and to determine preference indices for commonly consumed plants in western South Dakota.