Habitat selection, survival, and disease risk of semiaquatic mammals in a highly altered landscape

Abstract

Landscape change in the Midwest, USA has resulted in drainage of most wetlands and isolated those that remain. Semiaquatic species occurring in this region must adapt to novel landscapes and mortality risks and variable environmental conditions. I used 6 years of presence-absence data and information from radiomarked individuals to evaluate habitat selection, survival, and disease risk of semiaquatic mammals in east-central, Illinois. Annual model-averaged occupancy estimates of stream sites were correlated positively to summer precipitation for both American mink (Neovison vison) and muskrats (Ondatra zibethicus) suggesting a possible climate-change effect. Factors interplaying across multiple scales influenced occupancy dynamics of mink in stream habitats. Stream sites closer to permanent wetlands had lower occupancy and colonization rates for mink. Occupancy and colonization rates for mink were higher at sites with deeper water, and colonization rates were related negatively to urban land cover. Additionally, mink were more likely to leave stream habitat if muskrats were not present and permanent wetlands were nearby, highlighting the importance of supplementary habitats and prey availability. As predicted, male mink were more likely to use terrestrial habitat than female mink. When integrating habitat use and known-fate survival analysis, I demonstrated that use of terrestrial habitat exposes mink to elevated risk of mortality. Weekly survival rates of mink were lower when using terrestrial habitat. Mink also had reduced survival during the mating season, males had lower weekly survival rates than females, and subadults had lower weekly survival rates than adults. My results also revealed that exposure risk of semiaquatic mammals to the parasite Toxoplasma gondii is likely facilitated by modified drainage practices common in agricultural and urban landscapes. My studies highlight how environmental change has affected habitat use, survival, and disease risk of semiaquatic mammals occurring in a human-dominated landscape.