A highway reconstruction project is currently underway in west-central Montana expanding Hwy 93 from 2 lanes to 4 over a distance of approximately 45 miles. Portions of this highway bisect wetlands, which support a variety and abundance of wildlife. As one wildlife mitigation approach, 3 drainage culverts were modified to encourage movement between fragmented wetlands. Metal shelves were installed to allow animal movement during periods of high water. The current project evaluated the effectiveness of these shelves. Six culverts were studied, 3 with shelves (experimentals) and 3 without (controls), from January to September, 2001. Passive infrared TrailMaster cameras were mounted on the roof of each culvert 15 m from one entrance. Cameras were positioned so that mammals traversing culverts either on the floor or on shelves would be photographed. Cameras were checked weekly and film was replaced as needed. Each month small mammal populations adjacent to each culvert were censussed using Sherman live traps. Habitat characteristics adjacent to each entrance were described. This experimental design provided data on which mammal species were present and which were using culverts to move between wetland sites. Seasonal use and use of shelves during high water were assessed. Trapping identified 7 mammal species adjacent to culverts; of these, photographs demonstrated culvert use by deer mice, skunks, short tailed weasels, muskrats, raccoons, and domestic cats. During wet periods smaller species (e.g., deer mice, short tailed weasels) used the shelves. Tentative conclusions suggest that several species readily use shelves when water would otherwise prevent movement. However, movement occurs along the solid frame supporting the self rather than over the floor surface. Meadow voles, though abundant close to culverts, fail to use them, suggesting a barrier effect. Species presence is clearly affected by vegetative characteristics at these sites.