Abstract
In an environment increasingly dominated by roads, wildlife crossing structures (WCS) have been installed to decrease wildlife mortality and improve habitat linkages. In South Texas, vehicle collisions have been a major mortality source for the endangered ocelot (Leopardus pardalis). To mitigate threats to this species, eight WCS, along with associated fencing, were strategically placed along Farm-to-Market Road 106 (FM106), which passes through ocelot habitat. We assessed the rate of on-roadway crossings and WCS use by GPS-collared animals before, during, and after WCS installation using camera traps to verify WCS use. Because of the rarity of ocelots in this region, we supplemented ocelot data with data from bobcats (Lynx rufus), a similarly sized felid with slightly more general habitat preferences. Thirty-five animals, 30 bobcats, and 5 ocelots were tracked using GPS collars between 2013 and 2021. We observed a decline in the total number of crossings and on-roadway crossings of FM106 for both ocelots and bobcats over the duration of the study, despite controlling for factors such as an individual animal's proximity to FM106. There were 37 documented crossings using WCS by GPS-marked bobcats while their collars were active. However, the rate of on-roadway crossings during the post-construction period was still higher than the WCS use rate for both species. Animals were more likely to make on-roadway crossings during nighttime especially during unusually bright nights. While controlling for other factors, both species moved more quickly when making on-roadway crossings compared to WCS crossings or noncrossing intervals but moved more slowly when traffic levels were higher than expected for that time of day. Animals may take years to acclimate to the presence of WCS, suggesting that the use of these structures may increase over time. Additional fencing could further help limit high-risk road encounters by ocelots in this region.