Quantifying Ungulate–Rangeland Interactions: From Monitoring Free-Roaming Horse Condition to Vegetation Response Following Herbivore Exclusion
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Authors
Lieurance, Wade
Issue Date
2025
Type
Thesis
Language
en_US
Keywords
body condition score , camera trap , equid , exclusion , monitoring , winterfat
Alternative Title
Abstract
Reliable assessment of herbivore condition and vegetation response is essential for understanding grazing impacts across arid rangelands. This thesis integrates two complementary studies that address these challenges at different scales. The first develops and validates a quantitative framework for calibrating free-roaming horse body-condition scores from camera-trap imagery, comparing observer and veterinarian assessments to correct qualitative bias. The second analyzes a seventeen-year record of herbivory removal in a winterfat-dominated community in southeast Oregon, modeling long-term vegetation and soil responses to exclusion of ungulates and jackrabbits. Bayesian mixed-effects models reveal that ungulate exclusion increased winterfat, cyanobacteria, lichen, moss, and annual cover while decreasing soil compaction. Rabbit exclusion further increased winterfat and annual forb cover while decreasing annual graminoid cover, and showing diverging results in soil compaction. Together, these studies advance rangeland monitoring by combining methodological rigor with long-term ecological inference, offering practical tools for managing herbivore–vegetation interactions across western landscapes.