Skip to main content
U.S. flag

An official website of the United States government

Wildlife underpass use and environmental impact assessment: A southern California case study

December 10, 2018

Environmental planners often rely on transportation structures (i.e., underpasses, bridges) to provide connectivity for animals across developed landscapes. Environmental assessments of predicted environmental impacts from proposed developments often rely on literature reviews or other indirect measures to establish the importance of wildlife crossings. Literature-based evaluations of wildlife crossings may not be accurate, and result in under-estimation of impacts or establishment of inappropriate mitigation measures. To investigate the adequacy of literature-based evaluations, we monitored wildlife use of a freeway underpass that had been identified as critically important to wildlife connectivity, and which was evaluated in an environmental review document. Photographs were obtained from a network of trail cameras over 3 years. Six mid- to large-sized native mammal species used the underpass and two other mammal species were photographed near the underpass but not using it. American badger (Taxidea taxus) was photographed at a higher rate in the underpass than in the surrounding area. Gray fox (Urocyon cinereoargenteus) was rarely detected in the underpass relative to surrounding habitats, whereas the absence of mule deer (Odocoileus hemionus) in the underpass was unexpected, given relatively frequent detection in adjacent habitats. These results differed from the environmental assessment in that American badger was listed as "potentially" present while mule deer were expected to use the underpass. Results underscore importance of gathering data to document wildlife use of corridors, because some species do not or rarely take advantage of apparently suitable corridors, while others may be present when assumed to be absent.

Citation Information

Publication Year 2018
Title Wildlife underpass use and environmental impact assessment: A southern California case study
Authors Travis Longcore, Lindsay Almaleh, Brittany Chetty, Kathryn Francis, Robert Freidin, Ching-Sheng Huang, Brooke Pickett, Diane Schreck, Brooke Scruggs, Elise Shulman, Alissa Swauger, Alison Tashnek, Michael Wright, Erin E. Boydston
Publication Type Article
Publication Subtype Journal Article
Series Title Cities and the Environment
Index ID 70201245
Record Source USGS Publications Warehouse
USGS Organization Western Ecological Research Center

Related Content