Effects of a highway and mitigation projects on bobcats in Southern Texas

Roads are a common landscape feature that may negatively impact wildlife. These impacts may be reduced by altering roads and their right-of-ways. We studied impacts of a 4-lane divided highway on bobcats (Lynx ruffs) in southern Texas. From June 1997 to May 1999, 25 bobcats were found dead on the 32.2 km section of highway we studied. Mortalities were more likely adjacent to habitat preferred by bobcats and in sections of the highway in which thornshrub had been left in the median. Bobcats used culverts to cross under the highway and for other activities, such as resting. Culvert use was positively related to the openness ratio (width x height/length) of the culvert and to the amount of thornshrub cover adjacent to the culvert. Sections of fence 100 m long erected to funnel wildlife toward culverts did not increase bobcat use of culverts in an analysis of all culverts, but may have increased use of high-use culverts. Our results highlight the competing nature of techniques to minimize population fragmentation and mortality. Projects to reduce the impact of roads on wildlife should consider which impacts are likely to be most detrimental and ensure that efforts to mitigate one impact will not increase another. (C) 2003 Elsevier Ltd. All rights reserved.