Date of Award:

12-2021

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Ecology

Committee Chair(s)

Daniel R. MacNulty

Committee

Daniel R. MacNulty

Committee

Mary Conner

Committee

Johan T. du Toit

Committee

David N. Koons

Committee

Michael H. Cortez

Abstract

The reintroduction of wolves (Canis lupus) to Yellowstone National Park starting in 1995 is an important case study for understanding the consequences of predation on a prey population. Simulation studies conducted prior to and shortly after wolf reintroduction predicted that wolf predation of elk (Cervus canadensis) would have a modest influence on elk abundance. Predation of elk by wolves has been well documented and elk have remained the primary prey for wolves despite a decline in elk abundance. I used two quantitative approaches to estimate the influence of wolf predation on adult female elk survival and abundance in northern Yellowstone and adjacent Montana during 2000-2017. My results suggest that, while wolves did kill adult female elk aged 2-14 years old, these elk generally had high survival. Elk were more likely to be killed by wolves as they aged. Wolf predation of adult female elk was primarily restricted to older individuals that generally comprised a small proportion of the total elk population. Harsh environmental conditions, such as heavy snow, increased mortality of adult elk, but elk aged 2-9 years old retained high survival regardless of the environmental conditions. The observed decline in elk abundance across the 17-year study was primarily due to mortality of 2-14 year-old elk that died due to causes unrelated to wolves, including malnutrition, harvest, and other predators. I could not estimate the full impact of wolves on female elk abundance because of the lack of data on elk calf and yearling mortality. However, wolves likely had a smaller impact on the elk population than did non-wolf causes of elk mortality. These findings clarify how the impact of predation on a prey population may be limited by the age of the prey that are consumed and the relative importance of the predated individuals to the population (i.e., their reproductive potential).

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