Date of Award:

8-2023

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Wildland Resources

Committee Chair(s)

David C. Stoner

Committee

David C. Stoner

Committee

Kathryn A. Schoenecker

Committee

Kezia R. Manlove

Abstract

A non-native is a species that evolved in one ecosystem and has established within another. Non-native species can thrive in new ecosystems as they can spread quickly, outcompete and replace native species, and disrupt food webs. Domestic horses were brought to North America by Europeans in 1493. They are now found in 11 states across the western United States. Feral horses can negatively impact vegetation, endangered species habitat, compete with native species, and be important prey for mountain lions under certain conditions. But do feral horses affect the food web? Feral horses are managed by large removals to reduce the population, and therefore this food source can quickly decrease. I addressed two questions in Southeast, NV where, a horse removal occurred in December 2020 (455 horses; 45% of the population): (1) following removals, do mountain lions increase predation on native species, such as mule deer or bighorn sheep? and (2) Do mountain lions select feral horses over native species? I hypothesized: (1) horses will decrease from the diet and native prey will increase, and (2) mountain lions will select for native prey over feral horses. I deployed 49 cameras to determine prey availability and investigated 1,360 potential kill sites from 29 GPS-collared mountain lions. Prey was found at 1,056 sites. To test if mountain lions preyed more native species post-removal, I compared their diet in the years pre- and post-removal. I found that the diet did not change between years, indicating that they consumed horses and native prey similarly. To test if mountain lions were selecting for native prey, I compared each mountain lion's diet to their prey availability. The results showed mountain lions selected for horses during the growing season, while another two selected for deer during winter. Overall, feral horses made-up about 36% of the diet, with some individuals consuming horses more than others. In total, 342 horses were consumed by mountain lions during this study. I concluded that feral horse presence influences mountain lion predation behaviors, which is important for mountain lion and feral horse management in arid ecosystems that have many prey species

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