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Fire is being reintroduced to restore native mixed-grass prairie that has been invaded by woody vegetation and introduced species of grasses at 8000-ha (20,000-ac) Des Lacs National Wildlife Refuge (NWR) in northwestern North Dakota. Implications of this management for much of the local fauna are merely speculative without basic inventory data. We measured the occurrence and habitat relationships of small mammals (< 450 g [< 1 lb]) in prairie and woodland on the refuge. Using snaptraps, we captured 7 mammal species on 42 75-m (245-ft) radius plots in prairie during summer 1998 (n = 193 individuals in 5,208 trap-nights) and 5 species on 32 11-m (36-ft) radius plots in woodland during summer 2000 (n = 289 individuals in 2,560 trap-nights). We found 13-lined ground squirrel (Spermophilus tridecemlineatus) and western jumping mouse (Zapus princeps) almost exclusively in open prairie and southern red-backed vole (Clethrionomys gapperi) almost exclusively in woodland. Based on logistic regression analysis, occurrence of 13-lined ground squirrel related inversely to vegetation height, which generally decreases in northern mixed-grass prairie when recurrent fire is returned. Reintroduction of fire likely will expand the local distribution of 13-lined ground squirrel and western jumping mouse while decreasing that of southern red-backed vole.