Use of Highway Undercrossings by Wildlife in Southern California
Biological Conservation 115 (2004) 499–507 www.elsevier.com/locate/biocon Use of highway undercrossings by wildlife in southern California Sandra J. Nga,b, Jim W. Dolea, Raymond M. Sauvajotb,*, Seth P.D. Rileyb, Thomas J. Valonec aDepartment of Biology, California State University, Northridge, CA 91330-8303, USA bNational Park Service, Santa Monica Mountains National Recreation Area, 401 West Hillcrest Drive, Thousand Oaks, CA 91360, USA cDepartment of Biology, St. Louis University, St. Louis, MO, USA Received 13 June 2001; received in revised form 15 February 2003; accepted 20 March 2003 Abstract Roads, especially large highways, can have significant impacts on wildlife movement and survival. This is especially true for wide- ranging species, such as mammalian carnivores. Some of these impacts may be mitigated if wildlife can find and utilize passageways under highways. To determine if underpasses and drainage culverts beneath highways are used by wildlife as movement corridors, we monitored 15 such passages near Los Angeles, California using remotely triggered cameras and gypsum track stations. We found that passages were used by a variety of species, including carnivores, mule deer, small mammals, and reptiles. Many types of undercrossings were utilized, indicating that passages beneath highways, even when not originally designed for wildlife, can provide important safe avenues for animals to cross roads. For mammals of conservation concern, including native carnivores and deer, passage dimensions, surrounding habitat, and the extent of human activity were assessed to determine if these factors influenced passage use by these species. Our results show that while many native mammals used passages beneath highways, the presence of suitable habitat on either side of the passage was a particularly important factor predicting use.
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