Roads and highways act as barriers to wildlife. They disrupt movement of wildlife populations and connectivity between communities of interacting species. Transportation organizations and many wildlife agencies see highway crossing structures for wildlife as critical to mitigating highway barrier effects. These structures are optimistically assumed to be effective for most species, most of the time, but are seldom critically investigated.
Wildlife use of highway crossing structures can be highly variable and dependent on structural attributes, human use, and traffic conditions. Studies of animal behavior suggest that wildlife aversion to roadways—and possibly to crossing structures—could be related to traffic noise and light. If transportation organizations and wildlife agencies can confirm this effect they may be able to design more effective wildlife crossing structures and manage existing structures to increase their use by wildlife.
This policy brief discusses findings from research that measured traffic noise levels and used camera traps placed at 20 bridges and culverts in California that were known from previous work to pass at least one species.