Thesis
A SUMMER FEAST ATOP THE CROWN OF THE CONTINENT: THE INTERPLAY OF GRIZZLY BEARS AND ARMY CUTWORM MOTHS ACROSS GLACIER NATIONAL PARK'S ALPINE TALUS SLOPES
Washington State University
Master of Science (MS), Washington State University
01/2022
DOI:
https://doi.org/10.7273/000004540
Handle:
https://hdl.handle.net/2376/124967
Abstract
Army cutworm moths (Euxoa auxiliaris) migrate to high elevation Rocky Mountain talus slopes from July to September to escape arid conditions in low elevation areas. While residing in the Rockies, the moths forage at night on alpine wildflowers, metabolizing the nectar into fat, thereby changing their body composition to approximately 70% lipids (and 25% protein). During daylight periods, army cutworm moths aggregate in prodigious quantities within subsurface talus slopes. In mountain ranges of Wyoming and Montana, the moths’ summer migration overlaps occupied grizzly bear (Ursus arctos horribilis) range. Army cutworm moths are one of the most nourishing food resources available to mountain dwelling grizzlies. Their aggregations attract grizzlies to dig up moths from talus by the thousands each day across summer months. In Glacier National Park, Montana, grizzly bear foraging for army cutworm moths within alpine talus slopes remains poorly understood. To better understand the distribution of army cutworm moth aggregations and grizzly bear foraging at these congregations, we implemented systematic ground surveys to record moth presence-absence and aerial surveys to record grizzly bear foraging presence. We used the resulting data to develop 1) generalized linear models of army cutworm moth probability of occurrence and 2) relative suitability distribution models of grizzly bear moth foraging areas. Our results indicate environmental predictors of army cutworm moth occurrence and grizzly bear foraging overlap considerably. We found army cutworm moth occurrence is influenced by elevation, geological characteristics of talus slopes, terrain wetness, and photosynthetic activity. Further, we determined grizzly bear foraging for moths is primarily predicted by moth occurrence and slope, with terrain wetness also contributing. Grizzly bear-army cutworm moth interactions occur throughout Glacier’s alpine, particularly within the park’s highest massifs, which are centers of activity for this remarkable predator-prey association. While widespread, these areas comprise less than 0.3% of the park’s total land area. This research enhances our understanding of grizzly bear use of this nourishing food resource in Glacier and provides useful information to managers for conserving these habitats in the future, amid growing pressure from off trail recreators and changing climatic conditions.
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Details
- Title
- A SUMMER FEAST ATOP THE CROWN OF THE CONTINENT
- Creators
- Erik Peterson
- Contributors
- Daniel Thornton (Advisor)John Waller (Committee Member)Charles T Robbins (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Agricultural, Human, and Natural Resource Sciences, College of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University
- Number of pages
- 123
- Identifiers
- OCLC#: 1370911482; 99900898136701842
- Language
- English
- Resource Type
- Thesis