Transportation infrastructure effects on wildlife in California: Mountain lions in southern California as a case study

Winston Vickers, UC Davis Wildlife Health Center

Transportation infrastructure is widely recognized as having potential negative impacts on wildlife, from direct mortality in collisions with vehicles, disruption of natural behaviors by associated noise and light, and barrier effects that disrupt gene flow and other metapopulation dynamics.  Additionally, development tends to follow transportation corridors, furthering fragmentation effects on wildlife populations.  In California, especially in southern California, many highways are wide and heavily traveled which amplifies negative impacts on some wildlife species.

Our team at the University of California-Davis Wildlife Health Center has been studying mountain lions in southern California for nearly two decades and collaborating with other researchers and highway and conservation entities across the state to help understand the impacts of infrastructure on this and other wildlife species.  Mountain lions, because of their mobility and wide-ranging nature might be expected to be able to overcome most of the negative effects of highways.  However recent research suggests that despite their speed and mobility on the landscape, mountain lions in California are being restricted by highways and associated development, and the statewide population has become genetically fragmented.  Some subpopulations in southern California are threatened with extirpation because of genetic isolation and inbreeding, highway-related mortality, and other factors.
These research findings have helped to sharpen the focus on wildlife connectivity throughout the state, and especially in southern California.   As a result, projects to define key wildlife corridors, planning and implementation of highway modifications, and incorporation of wildlife passages into new highway construction have been implemented or are in the planning stages.
We will present an overview of the transportation-related issues for wildlife in California using the mountain lion as an example, and detail some of the research that is helping to guide efforts to improve wildlife connectivity across highways.  We will present examples of basic research that is critical to finding the best solutions, projects that have been successful, and how collaborative approaches in planning and implementation are improving wildlife connectivity.  We hope that these examples can help guide efforts elsewhere in the nation and the world as climate change and development pressures make wildlife connectivity more and more of a concern.