Influence of grazing by bison and cattle on deer mice in burned tallgrass prairie

We studied the influence of grazing by bison (Bos bison) and by cattle (B. taurus) on deer mice (Peromyscus maniculatus) in tallgrass prairie at the K onza Prairie Biological Station in 1997 and 1998. Small mammals were sample d by one 10-station trapline in each of four bison-grazed enclosures, four cattle-grazed enclosures and four ungrazed sites. Enclosures were 4.9 ha an d the biomass of grazers in each was similar. All sites were burned annuall y. We sampled small mammals for 4 consecutive nights in spring before fire, in spring after fire and in autumn. Deer mice were the most abundant speci es (n = 285; 83% of all small mammals) captured in all treatments and in ea ch trapping period. Deer mice were significantly more abundant in bison-gra zed and cattle-grazed sites than in ungrazed sites in spring before fire (P < 0.01 and P < 0.05, respectively), but were similar in abundance in graze d and ungrazed sites following fire. Abundance of deer mice was significant ly higher in bison-grazed sites than in cattle-grazed and ungrazed sites in autumn (P < 0.05 and P < 0.001, respectively). Bison and cattle differ in grazing and nongrazing behaviors (e.g., wallowing by bison) that result in differences in vegetation structure. It is likely that differences in deer mouse abundance between bison-grazed and cattle-grazed treatments were due to differences in vegetation structure caused by the two types of grazers.