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Title:Habitat, landscape, and climate effects on riparian predator-prey interactions in a human-dominated ecosystem
Author(s):Wolff, Patrick
Advisor(s):Schooley, Robert L.
Department / Program:Natural Res & Env Sci
Discipline:Natural Res & Env Sciences
Degree Granting Institution:University of Illinois at Urbana-Champaign
habitat selection
predation risk
Abstract:Predator-prey interactions form ecologically significant links between terrestrial and aquatic ecosystems, and may be particularly important in riparian ecosystems with highly variable habitat features in human-dominated landscapes. Climate models predict an increased frequency of summer drought and spring flooding events in the Midwestern United States. This variability in precipitation will alter within-stream habitat structure, and will affect predator-prey interactions in riparian ecosystems. I studied (1) habitat selection of a semiaquatic predator as it relates to the spatial distribution of a main prey, and (2) predation risk for an aquatic prey from a variety of aquatic and riparian predators. I examined the seasonal diet of American mink and determined if a primary prey, crayfish, was an important driver of habitat selection during the summer of a severe drought year. I collected mink scats in three seasons. In summer 2012, I performed occupancy surveys for mink and concurrently measured crayfish densities and habitat features in 59 stream segments in east-central Illinois. Occupancy modeling showed that mink selected locations based directly on high prey concentrations instead of habitat characteristics that might indicate high prey densities. Mink shifted strongly to feeding mainly on crayfish during summer, and mink were more likely to occupy stream segments that contained crayfish hotspots. Mink were also negatively associated with both urbanization and stream size. I also compared predation risk for crayfish in a year of severe drought (2012) to a non-drought year (2013). I evaluated the effects of crayfish size, within-stream characteristics, and landscape context on crayfish mortality between years. I conducted an experiment in which tethered crayfish were exposed to aquatic and riparian predators for 3 nights in 45 stream segments in east-central Illinois. Different stream conditions caused the factors most influential on predation risk to differ between years. Crayfish mortality was lower (43%) during the drought than in the wet year (52.0%). Aquatic predators were predominant, but there was a shift to increased predation by terrestrial predators during the drought. During the drought, submerged vegetation cover had the greatest effect on predation risk; crayfish survival was higher where crayfish could find refuge in submerged vegetation. In the non-drought year, crayfish size was the most influential variable affecting predation risk; larger crayfish suffered higher mortality than smaller crayfish. Crayfish mortality was related positively to stream size, and negatively to urbanization in both years. My research demonstrates that habitat selection and predation risk are spatially and temporally dynamic, but patterns exist that help explain predator behavior and prey vulnerability.
Issue Date:2014-01-16
Rights Information:Copyright 2013 Patrick Wolff
Date Available in IDEALS:2014-01-16
Date Deposited:2013-12

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