Assessing Intra-Seasonal Changes in Summer Elk Diet Composition

Author

Ava E. Window, University of Montana, MissoulaFollow

Graduation Year

2025

Graduation Month

May

Document Type

Thesis

Degree Name

Bachelor of Science

School or Department

Wildlife Biology

Major

Wildlife Biology – Terrestrial

Faculty Mentor Department

Wildlife Biology

Faculty Mentor

Chad Bishop

Faculty Reader(s)

Dr. Chad J. Bishop, Dr. Meredith A. Zettlemoyer, Dr. Joshua J. Millspaugh, Dr. Mark Hebblewhite, Dr. Kelly Proffitt, Trevor C. Weeks,

Keywords

Cervus canadensis, forage quality, forage quantity, nutritional ecology, phenology, Montana

Subject Categories

Other Animal Sciences | Other Ecology and Evolutionary Biology | Terrestrial and Aquatic Ecology | Zoology

Abstract

Elk (Cervus canadensis) require adequate forage to fulfill their seasonal nutritional requirements. Elk undergo their highest nutritional demands during summer to support critical life functions such as late gestation, lactation, and juvenile growth. However, variations in plant phenology significantly influence the quality and quantity of forage available to elk during the summer season. As summer advances and plant communities mature, forage quality often declines, leading to a landscape that imposes greater nutritional constraints on elk. As a result, prior research on elk foraging habits has primarily focused on late summer. This has led to limited knowledge surrounding the intra-seasonal dynamics of elk diet composition across the entire summer season. Exacerbating this, growing evidence suggests that both early and late summer forage often fail to meet the nutritional demands of lactating and reproducing female elk.

To address this knowledge gap, we examined how forage phenology and availability influenced changes in elk diet composition between early and late summer. We utilized data from two elk populations in western Montana that resided in landscapes shaped by differing disturbance regimes (timber harvest, wildfire) and climates. Using DNA metabarcoding of fecal samples, we assessed intra-seasonal changes in diet composition from early to late summer via Principal Component Analyses (PCA).

Our PCA revealed a significant intra-seasonal shift in elk diets within the Noxon study area, whereas diets in the Blackfoot study area remained stable throughout the entire summer season. We determined that phenological changes in forage quality influenced elk diet composition in both study areas and drove the intra-seasonal shift observed in the Noxon study area. Conversely, the dietary stability observed in the Blackfoot study area resulted from the sustained presence of high quality forage throughout summer, combined with high overall biomass of an early successional forage species following a recent fire. Collectively, our findings contribute to the understanding of elk forage utilization in western Montana ecosystems and provide insights to inform habitat management approaches that explicitly consider elk diets across the entire summer season.

GLI Capstone Project

no

Recommended Citation

Window, Ava E., "Assessing Intra-Seasonal Changes in Summer Elk Diet Composition" (2025). Undergraduate Theses, Professional Papers, and Capstone Artifacts. 569.
https://scholarworks.umt.edu/utpp/569