Succession of Mammals in a Disturbed Area of the Great Plains

Abstract

Effects of historic and continuing disturbance on the flora and mammalian fauna at Barr Lake State Park, Adams County, Colorado, were assessed. Construction of an impoundment and irrigation canal enabled development of a riparian zone that initially increased the richness of the mammalian fauna by nine species. Subsequent conversion of nearby rangeland to cropland decreased the richness of the fauna by as many as 12 species. Mid-summer drawdown of the lake for irrigation possibly promotes disturbance vegetation and disrupts populations of small mammals. Agricultural practices on the Great Plains have had both pronounced and subtle effects on native prairie. Some of these effects are intensified by sparse precipitation or by agricultural activities intended to circumvent sparse precipitation. Although agricultural activity has increased in recent years, the effects of these practices on the native flora and fauna of the Great Plains have received little attention. Grant et al. (1982) investigated the impacts of grazing on structure of vegetation and composition of small mammals, whereas Moulton et al. (1981) hypothesized that native species of mammals eventually recolonize areas subjected to disturbance if adequate avenues of dispersal exist and if the structure of the vegetation remains similar. Most studies of the impact of agricultural practices on the plains (e.g., Judd and Jackson, 1939; Costello, 1944; Judd, 1974) focused on secondary succession of plants leading toward reestablishment of natural plant communities on abandoned cropland after termination of alternative practices. The objectives of this investigation were to compare the historic flora and mammalian fauna with those currently found at Barr Lake State Park, Adams County, Colorado, and thereby to characterize succession of mammals in an area of the Great Plains subjected to continuing disturbance.