As roads continue to be built and expanded, it is important that managers understand the effects that vehicle-related mortality can have on the population dynamics of wildlife. Our objective was to examine the frequency of mule deer (Odocoileus hemionus) vehicle collisions to determine if different demographic groups showed differential susceptibility to mortality when compared with their proportion in the population. We also compared vehicle collision rates of mule deer, elk (Cervus canadensis), and moose (Alces alces) to determine their relative vulnerability to vehicle collisions. We found that 65% of mule deer involved in vehicle collisions were female; of those, 40% were adult does ≥2？yrs. When we compared the proportion of bucks, does, and fawns killed in vehicle collisions to surveys of live deer, we found that bucks were killed at rate of 2.1–3.0 times their proportion in the population. Additionally, when we compared vehicle collision rates for 2010 and 2011, we found that mule deer were 7.4–8.7 times more likely to be involved in collisions than elk and 1.2–2.0 times more likely than moose. However, we were unable to detect a negative correlation () between mule deer abundance and increasing traffic volume. 1. Introduction Roads are being built and expanded throughout the developed world to accommodate the increasing human population and demand for transportation of people, goods, and materials [1–3]. An IEA 2013 report  suggested the following: the world will need to add nearly 25 million paved road lane km (~60% increase) between 2010 and 2050; between 45？000 and 77？000？km2 of new parking spaces will be added to accommodate passenger vehicle stock growth; global travel in 2050 will double that of 2010 travel levels; passenger travel will account for 70% of this growth; and ~90% of travel growth is expected in developing countries. Laurance et al.  estimated that the total length of the projected new roads is equivalent to encircling the earth ~600 times. Clearly, it is increasingly important to understand the effects that roads have on wildlife; those effects appear to be overwhelming negative for most species [6–9]. Deer are commonly involved in vehicle collisions in Europe, North America, and Japan [10–12]. In the United States alone, there are an estimated 1-2 million vehicle collisions with large animals annually, most of which involve deer, that result in >$8 billion (USD) in damages and >200 human fatalities [13–15]. Additionally, vehicle collisions are nearly always fatal for deer . Mule deer occur throughout western North
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