Mechanisms Underlying Increased Nest Predation Near Natural Gas Development
Abstract
Habitat loss and alteration resulting from human activities are affecting wildlife species around the globe. Mechanisms underlying such effects are rarely investigated or known, yet are critical for effective mitigation. The sagebrush ecosystem in particular has been extensively fragmented by human activities such as oil and gas extraction, leading to direct habitat loss and habitat fragmentation / conversion. Sagebrush-obligate songbirds are experiencing population declines across the Intermountain west and are species of concern for multiple state and federal agencies. Improved understanding of the effects of habitat change on sagebrush-obligate songbirds, and the associated mechanisms responsible for these effects, is therefore of great interest to conservation practitioners. Previous work demonstrated lower abundance of sagebrush songbirds with increased surrounding habitat loss due to natural gas development in western Wyoming, and showed that increased nest predation was at least partly responsible. We know that rodents are the primary nest predators of sagebrush songbirds, and that rodents are also more abundant near energy development. What remains unclear is why rodents are more abundant in areas surrounding natural gas fields, which is the primary focus of my thesis research. My research focused on investigating two alternative hypotheses for the potential mechanism driving rodent abundance, and thus songbird nest survival, near development. Based on the mesopredator release hypothesis I predicted that a reduction in apex predator activity near development was releasing rodents from predation, thereby allowing local population growth. In areas with increased habitat loss from natural gas development I documented increased detections of apex predators, increased perceived predation risk for rodents, and decreased survival of rodents. Strong inference necessitates eliminating alternative hypotheses, and I identified three lines of evidence suggesting rejection of the mesopredator release hypothesis. I also aimed to identify the specific components of habitat loss on natural gas fields more important for nest predators. Reclaimed areas best explained patterns of deer mouse abundance, with increased abundance of rodents in areas with more surrounding reclaimed areas. Mice moved through and ate plants found in reclaimed areas, but did not derive any fitness benefits from living near re-seeded areas. Reclaimed areas do appear to be attracting large numbers of deer mice, but the positive effects of living near development may be mediated by increased predation pressure in these areas. By carefully testing hypotheses about how natural gas development affects the primary nest predators of declining sagebrush-obligate songbirds, I have demonstrated the value of a mechanistic approach to wildlife science. My results provided specific suggestions for how natural gas developers and land managers may adjust practices to mitigate the negative effects of development on co-occurring songbirds of concern. For example, keeping non-native species out of reclaimed areas may reduce the desirability of these sites for deer mice. Given the increased intensity of energy development within the western U.S. and the potential for expanding development in the future, a mechanistic understanding of wildlife responses to development is imperative for future management strategies and conservation plans for vulnerable species living within a matrix of energy development.
- Publication:
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Masters Thesis
- Pub Date:
- 2017
- Bibcode:
- 2017MsT.........81S
- Keywords:
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- Wildlife conservation;Wildlife management;Energy