Date of Award
Master of Science (MS)
Biologists estimate that less than 50 endangered ocelots (Leopardus pardalis) remain in the United States, restricted to two small populations in Cameron and Willacy Counties located in deep south Texas. Conversely, bobcats (Lynx rufus) are abundant in south Texas; however, two of the biggest threats to both species are vehicle collisions and habitat fragmentation. To mitigate these threats, the installation of wildlife crossings has been proposed to decrease the number of road mortalities, and wildlife corridors have been suggested as a useful tool for providing increased habitat connectivity. However, research on ocelot use of corridors and wildlife crossings in Texas is severely lacking. Due to overlap in daily activity, diet, and habitat, ocelots and bobcats may be exhibiting competition over resources where space to coexist without conflict is limited. This study used camera traps to document wildlife communities with a focus on ocelots and bobcats from October 2013 to October 2014 to test the following hypotheses: 1) Bobcat hourly activity will differ between locations where ocelots are present and absent. 2) Prey composition will be a significant indicator of felid presence. 3) Ocelot and bobcat presence will be correlated with differing plant species and levels of canopy cover. 4) Wildlife diversity indices will be similar within corridor types and will differ between corridor types. 5) Wildlife community composition and diversity indices will differ between proposed wildlife crossings and corridors not adjacent to Farm-to-Market Road (F.M.) 106. Cameras were placed within four structural habitat types: brush strip, resaca (oxbow lake) edge, drainage ditch, and brush patch. Structural habitat variables were surveyed to analyze habitat preferences of ocelots and bobcats in corridors. Fifty-eight species were identified at 52 cameras. Eight of the 16 known ocelots in the Cameron County population were surveyed. Bobcat hourly activity and prey frequency were different at cameras where ocelots were present and absent. Ocelots were associated with corridors (brush strip, resaca edge, drainage ditch) and not brush patches; high amounts of spiny hackberry, texas ebony, and goatbush; greater distance from F.M. 106; higher diversity of woody species >1m tall; and ground cover comprised of low amounts of grass, forbs, and bare ground, and high amounts of leaf litter, woody debris, and woody speciessmall, sparse brush patches in wildlife frequency and diversity, and brush strips had the greatest species richness and total number of individuals. Brush patches had a significantly lower number of individuals present when compared to corridors. Fifty percent of the known Cameron County ocelot population was observed using corridors, suggesting that functional corridors may be a valuable tool to promote connectivity of ocelot populations in Texas. Proposed wildlife crossing locations had lower diversity when compared to corridors not adjacent to F.M. 106. However, ocelots were recorded on both sides of F.M. 106, indicating that wildlife crossing structures under roadways should be effective in providing ocelots with a safe alternative to traversing over dangerous roadways.
University of Texas Brownsville