Year of Award

2021

Document Type

Dissertation

Degree Type

Doctor of Philosophy (PhD)

Degree Name

Wildlife Biology

Department or School/College

W.A. Franke College of Forestry and Conservation

Committee Chair

Joshua Millspaugh

Commitee Members

Roland Kays, Brady Allred, Jedediah Brodie, Paul Lukacs

Keywords

Camera trap, Cattle grazing, Community ecology, Mammal, Sustainability, Urbanization

Publisher

University of Montana

Abstract

Increases in habitat loss and fragmentation from anthropogenic disturbance present substantial threats to global biodiversity; thus, sustainable land management will be crucial to support current and future generations of humans and wildlife. In the western United States, approximately 70% of the land is grazed by domestic cows (i.e., “cattle”), and urban development is increasing rapidly. These land uses may affect vegetation composition and mammal communities, which could alter ecosystem function through bottom-up or top-down processes. Therefore, understanding the responses of vegetation and mammal communities to these practices is important when considering socio-ecological sustainability.

In this dissertation, I evaluated how cattle grazing and urban development affected vegetation dynamics and medium to large (>150 g) mammal community structure at multiple scales. First, I identified and quantified factors associated with vegetation change over the past 36 years on public lands grazing allotments across the western contiguous United States. Then, using multispecies occupancy models, Poisson count models, and daily activity patterns, I determined how cattle grazing on private ranches in western Montana and housing density surrounding Missoula, Montana influenced the spatiotemporal dynamics of mammal communities. Finally, I identified how residential yard management affected mammal relative abundance in Raleigh, North Carolina. At both continental and local scales, environmental and abiotic factors were generally more important drivers of vegetation and mammal community dynamics than cattle grazing. In contrast, housing development strongly influenced mammal community structure, with generally smaller-bodied, urban-adapted species occurring within higher housing densities. Further, supplemental feeding in residential yards was the strongest predictor of mammal abundance, compared with landscape-scale vegetation characteristics and predation risk.

My research demonstrates that cattle grazing on rangelands in the western United States has had relatively minor associations with vegetation production and mammal community dynamics at the stocking rates evaluated, although local-level management could dictate the strength of effects. In contrast, urban development strongly impacts mammal communities, but effects may vary across urban areas with different human population densities, urban structure, and ecological communities. Thus, conserving “working lands” that sustain human livelihood, while maintaining the natural biodiversity and function of the ecosystem, may facilitate socio-ecological sustainability.

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© Copyright 2021 Christopher Paul Hansen