Date of Award


Degree Name

Master of Science



First Advisor

Nielsen, Clayton


Large-scale, multispecies monitoring programs are used widely to assess changes in wildlife populations; however, they often assume constant detectability when documenting species occurrence. This assumption is rarely accurate because animal populations vary considerably across time and space. Furthermore, detectability of a species can be influenced by a number of physical, biological, or anthropogenic factors (e.g., weather, seasonality, topography, sampling methods, urban development). Analyses of habitat factors affecting occupancy and detection of mammalian species have not been conducted in the Paraguayan Chaco. To address this gap in the literature and provide conservation recommendations, I estimated site occupancy rates using species-specific detection probabilities for focal mammalian species at 3 study sites in the Chaco ecoregion of Paraguay. During remote camera surveys conducted August - November 2011 - 2012, I used photographic data and model selection techniques to assess the influence of different survey and site covariates on occupancy of several focal mammalian species: maned wolf (Chrysocyon brachyurus), Geoffroy's cat (Leopardus geoffroyi), puma (Puma concolor), crab-eating fox (Cerdocyon thous), pampas fox (Lycalopex gymnocercus), collared peccary (Pecari tajacu), white-lipped peccary (Tayassu pecari), South American tapir (Tapirus terrestris), and giant anteater (Myrmecophaga tridactyla). I recorded 2,034 photographs of 24 mammalian species at 64 camera sites; among those, 1,353 photographs and 529 independent survey-detections were of these 9 focal species. Detection of maned wolves and peccaries was higher in 2011 than 2012; other species did not show significant differences in detection by year. Peccaries were detected more frequently during higher temperatures, but foxes were detected more frequently during lower temperatures. The crab-eating fox was the species occupying the most sites (68%) and white-lipped peccary was the rarest, occupying only 30% of the study area. Anthropogenic disturbances (i.e., urban areas, paved roads, and human structures) negatively affected most species. Maned wolves and collared peccaries appeared to prefer grasslands, while puma and crab-eating fox used areas closer to water. White-lipped peccaries appeared to be most common or widely-distributed at the Toro Mocho study site. My research will provide land managers and conservation planners with an understanding of how mammals are distributed across the Paraguayan Chaco, as well as informing future decisions concerning land use and development by the rural human population. To further broad-scale conservation goals, wildlife biologists in Paraguay should seek partnerships with rural stakeholders to mitigate the effects of continuing agro-industrial development. Moreover, additional protected areas and buffers should be sought to maintain lands in natural conditions, including large areas set aside as wildlife reserves.




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