Response of Small Mammals to Livestock Grazing in Southcentral Idaho

Abstract

The effects of livestock grazing on populations of wildlife have been addressed in two recent studies on the INEL Site. However, studies were performed by measuring indices of abundance among areas where different practices had occurred prior to initlation of study. There is no proof that differences detected among the areas actually resulted from the land use practices. Studies should be conducted with replication and strict controls before correlated data can be accepted as indicators of cause and effect relationships. The large variation in the occurrence and densities of small mammals among areas with the same or similar uses suggests the need for further studies to resolve conflicting conchions. described (Johnson 1979, Reynolds and Trost 1980). Twenty-five specific study transects were systematically established over the INEL Site; 12 were in the central area, which has not been grazed by livestock for more than 20 years, and 13 were in the livestock grazed periphery. Each transect was 700 m long (Fig. I). Cattle and sheep grazed on separate allotments for several years prior to the study. Cattle generally grazed during winterand spring while sheep usually grazed during spring. Material and Methods Each end of transects was marked with an aluminum plate (18 X Recently four areas were studied on the Idaho National Engi18 cm) attached to an iron reinforcement stake. Piates were neering Laboratory (INEL) Site to compare the effects of sheep stamped with the transect number (l-25), the date of establishment grazing on vertebrate populations (Reynolds and Trost 1980). (July 1975) and the initials of investigators. Each transect number During the same period (1976 and 1977) 1 compared indices of was suffixed with a letter to indicate whether the location was small mammal abundance among 25 different areas on the INEL ungrazed (U), grazed (G), or near the common border for the areas Site. My data do not corrobrate the conclusions of Reynolds and (B). Five of the transects were near the border but each transect was Trost regarding small mammals, but identify site specific variation totally in or out of the grazed area. in small mammal abundance. Common plants in the vicinity of each transect were visually ranked as to abundance in July 1976. In April 1977, 50 point Study Areas locations were systematically chosen about each transect and the height of the shrub closest to each location was recorded. TwentyThe location and description of the INEL Site have been recently five points were placed on each side of a transect at 25m intervals. The author is assistant professor, School of Forestry and Wildlife Management, Each point was jrn from the transect. If no shrub occurred within 1 Louisiana State University, Baton Rouge, Louisiana 70803. m, then the height recorded was 0 m. At each of the same SO points This research was conducted under contract EY-76-S-071-1526 between the U.S. Department of Energy and Colorado State University. a 0.1-m? wire loop was placed in the ground and the number of Manuscript received May 28, 1980. cottontail (Syfvilagus spp.) pellets was counted. Simultaneously, JOURNAL OF RANGE MANAGEMENT 35(l), January 1982 51