Year of Award


Document Type


Degree Type

Master of Science (MS)

Degree Name

Environmental Studies

Department or School/College

Environmental Studies Program

Committee Chair

Len Broberg

Commitee Members

Cara Nelson, Marcel Huijser


Barrier, Branches, Connectivity, Cover, Highway, Mice, Movements, Roads, Shrews, Small mammals, Trees, Trunks, Underpasses, Voles


University of Montana


Crossing structures enable wildlife to safely cross highways by physically separating wildlife and vehicles. Most wildlife underpasses and overpasses are designed to accommodate a wide variety of species. Their suitability for individual species, however, varies by location (surrounding habitat), structure type (e.g. underpass or overpass), and dimensions (height, width, length). For some taxa, the habitat immediately adjacent to and inside an underpass or on top of an overpass is critical. For instance, small mammals, reptiles, amphibians and many invertebrates may avoid open areas because they require cover (e.g., live vegetation, tree stumps, branches, or rocks) to reduce predation risk and because of the microhabitat it provides (e.g., temperature, moisture). I investigated the effect of cover on the abundance and movements of small mammals in ten large mammal underpasses (approximately 7 m wide, 4 m high) along U.S. Hwy 93 North on the Flathead Indian Reservation, Montana. Track tubes recorded abundance of small mammals in and around 10 structures (5 control/ 5 treatment) in 2011 and 2012. I placed cover (dead tree limbs) inside half (five) of the underpasses in winter 2012 (“treatment”), while the remaining five underpasses served as control with no cover added. Capture-mark-recapture using live traps was conducted in the fall of 2012 to record abundance and movement of small mammals in and around the underpasses. There was no statistically significant effect of cover on small mammal abundance detected by track tubes or live traps. . There was a statistically significant effect of cover on movement between the right of way and crossing structure for small mammals detected by live traps. By placing cover inside wildlife underpasses, wildlife managers can increase crossing structure use by small mammals at minimal cost.



© Copyright 2013 Hayley R. Connolly-Newman