Year of Award

2026

Document Type

Thesis

Degree Type

Master of Science (MS)

Degree Name

Wildlife Biology

Department or School/College

Department of Ecosystem and Conservation Sciences/W.A. Franke College of Forestry and Conservation

Committee Chair

Mark Hebblewhite

Commitee Members

Thomas Riecke, Sarah Sells, Evelyn Merrill

Keywords

feral horses, competition, ungulate community dynamics, predator-prey interactions, apparent competition, diet overlap

Subject Categories

Biology

Abstract

Feral herbivores are expanding in range and numbers globally, yet their community-level effects in ecosystems are poorly resolved. We evaluated whether feral horses reshape predator–prey–vegetation dynamics in Alberta’s Upper Foothills, Canada, through two pathways; i) potential exploitative competition for forage and ii) apparent competition via shared predators. We combined fecal DNA metabarcoding with remote wildlife cameras to quantify diets, spatiotemporal co-occurrence, and the role of horses in carnivore diet. We analyzed 241 ungulate scats (feral horses, elk, bighorn sheep, cattle, moose, and deer), 96 combined camera-years at 23 sites, and 190 carnivore scats (wolves, cougars, coyotes, bears) from 2023–2025. The diet of feral horses, a bulk-grazing hindgut fermenter, was consistently graminoid-focused (~50% of diet) but broadened to include more forbs in summer (~40%) and shrubs in winter (~41%). Diet overlap was greatest between bulk grazers (horses–cattle) and between mixed feeders (elk–bighorn sheep). Feral horses overlapped with native herbivores on key forage during spring and winter seasonal bottlenecks. Horse and cattle spatiotemporal overlap and convergence on non-native forbs in summer suggests high potential for exploitative competition between non-native herbivores. Camera randomization tests indicated higher-than-expected summer co-occurrence of horses with cattle, moose, and cougars and lower-than-expected co-occurrence with elk, suggesting potential interference competition. Carnivore fecal metabarcoding revealed feral horses as a consistent prey resource. Wolf diet was dominated by deer but included substantial feral horse signal (~25%), coyotes showed broad diets with frequent horse detections (~28%), while cougars had a smaller proportion of horse in their diet (~5%). Grizzly bear samples containing prey DNA were limited (n=9). However, of these samples, feral horses contributed to ~33% of their meat diet. Carnivore diet provides a pragmatic first step for evaluating apparent competition. Together, results show preconditions for both exploitative and apparent competition between horses and native species. We outline decision-relevant next research steps:seasonal/age-specific horse mortality at verified kill sites and updated multi-species density estimates could help parameterize community models to guide adaptive management.

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