Large mammals are increasingly inhabiting a landscape altered by roads, fences, habitat changes, and other human activities — with myriad, often negative, consequences. My research aims to understand and mitigate some of these consequences. Through analyzing ungulate-vehicle collision patterns across Wyoming, I have identified the key "hotspots" of collisions. For mule deer, collisions are highest near agricultural land and in areas of high traffic volume and high speed limit — typically just outside major towns. In collaboration with the Wyoming Migration Initiative, we have analyzed deer migration and winter habitat-use patterns as they relate to deer collision patterns. This helps us to understand not just where deer get hit, but where roads impact their habitat connectivity. Ultimately this helps us to recommend where and what kind of mitigations should be considered. I am also working in close partnership with the Wyoming Department of Transportation to test various methods that may help to reduce the impacts of roads on ungulates.

Phenology shifts in the Tetons

The timing of ecological events, or phenology, is important to how species exist and interact with each other. But the timing of many events, such as when plants emerge and flower, when insects emerge, or when migratory birds arrive for the summer, is shifting as the climate warms. Understanding these shifts is important to planning how best to conserve ecosystems. I am working to gather historic and contemporary data on plant (and eventually insect and bird) phenology in the Tetons in order to assess how these patterns have changed. I am also working to set up a citizen science program, wherein citizen scientists can help make their own phenological observations and add them to our database. By encouraging people to observe changes that are occurring in their own ecological backyard, I hope to raise awareness about climate change and its impacts on our ecosystems.

Mutualism Disruption by invasive ants

In the savannas of East Africa, the widespread whistling-thorn acacia (Acacia drepanolobium) has a close relationship with several species of native ants. The ants defend the trees against elephants and other browsing herbivores, and the trees give the ants a home and food in the form of sugary nectar. This mutualism prevents elephants from destroying trees. But the invasive big-headed ant (Pheidole megacephala) is threatening this mutualism. My work has shown how this voracious invader attacks and kills off native ants, leaving trees defenseless against elephants. In places where the invasive ant has established, trees are five times more likely to be killed compared to places where native ants live on the trees. My colleagues and I are now starting to examine the cascading effects of this mutualism disruption. Since trees provide essential shelter for numerous animals, food for browsing herbivores, and soil nutrients for grasses (and grazing herbivores), loss of tree cover could have catastrophic consequences for a variety of species in a region of high conservation value.


Most of the Africa’s large mammals rely on unprotected land through at least part of their range. As human populations increase, wildlife are increasingly having to share the land with livestock. Can these two guilds of large mammals co-exist? This question applies equally to many other wildlife-rich rangelands around the world. As a PI of the Kenya Long-term Exclusion Experiment (KLEE), I work to understand how cattle and wildlife — separately and together — affect long-term savanna dynamics. Our research group has shown that cattle have a large number of positive effects on wildlife, suggesting that rangelands can be managed for both livestock production and wildlife conservation. Overgrazing by livestock, however, can have a variety of negative consequences for rangelands. Increases in woody cover ("bush encroachment") and decreases in grass cover, with associated soil erosion, are two of the most common impacts. Both reduce rangeland productivity and degrade habitat quality for wildlife. Through my research, I have shown how cattle contribute to bush encroachment and how many species of wild ungulates avoid areas of high woody cover because of fear of predation. I have also demonstrated how loss of grass and soil reduces ecosystem functions, but how simple restoration approaches can put some of these functions back and improve rangeland service provisioning for both wildlife and livestock. Through partnerships with ranch and conservancy managers, I work to answer practical questions and facilitate sustainable mixed-use of African rangelands.