Theses and Dissertations at Montana State University (MSU)
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Item Food resources for grizzly bears at army cutworm moth aggregation sites in the Greater Yellowstone Ecosystem(Montana State University - Bozeman, College of Agriculture, 2022) Lozano, Katerina N.; Chairperson, Graduate Committee: Robert K. D. Peterson; This is a manuscript style paper that includes co-authored chapters.Army cutworm moths (Euxoa auxiliaris) (ACM) migrate annually to peaks on the eastern edge of the Greater Yellowstone Ecosystem (GYE). Grizzly bears (Ursus arctos horribilis) feed on these moths from mid-to late summer. The Shoshone Forest is preparing a management plan to address the conservation of these sites and foraging bears. Increased human use and GYE-wide changes in grizzly bear food availability and related foraging patterns are concerns prompting plan preparation. This study addresses grizzly bear diet and vegetation foraging locations on a prominent moth site ('South Site'). A 1991 study identified 4 forb genera utilized by bears at ACM sites. A 2017-2018 study identified 5 more and postulated that biscuitroot (Lomatium spp.), found in high elevation meadows, was an important resource for grizzly bears. During 2020-2021 we clarified these findings using scat collection and descriptions of available vegetation. We determined the frequency and volume of food items in 298 scats. We quantified vegetation at peak meadows (elevation: 3,078 - 3,657-m) and in cirque basins (elevation: 3,658 - 3,931-m) to record the percent cover of nine forb genera. We also described the density of biscuitroot and craters where bears excavated roots to determine if biscuitroot influences foraging site choices for grizzly bears. We confirmed use of 7 of the 9 previously identified forb genera. The most frequently consumed foods by grizzly bears were ACM (23% volume) and roots and tubers (38% volume). Similarly, the 2017-2018 study found 20% ACM by volume and 45% roots and tubers by volume. There was a positive, linear relationship between the density of flowering biscuitroot and craters from grizzlies digging roots in several peak meadows (p < 0.001). Rather than foraging solely on ACMs, grizzly bears on this moth site relied highly on vegetation in their diet, specifically roots and tubers from biscuitroot and clover. Our findings suggest grizzly bears have a diverse diet at this moth site that may allow them to adjust to variations in ACM abundance. They focused foraging on roots and tubers at 5 peak meadows near talus where moth foraging occurs; information that can potentially help mitigate human-grizzly bear interactions involving climbers.Item Natal origin, migratory patterns, and abundance of the army cutworm moth, Euxoa auxiliaris(Montana State University - Bozeman, College of Agriculture, 2022) Dittemore, Clare Mikaela; Chairperson, Graduate Committee: Robert K. D. Peterson; This is a manuscript style paper that includes co-authored chapters.The army cutworm moth, Euxoa auxiliaris, is a migratory noctuid that migrates from and returns to the Great Plains. At their Rocky Mountain summering range, it is an important food for the Greater Yellowstone Ecosystem (GYE) grizzly bears, Ursus arctos horribilis. However, a limited understanding of moth migratory patterns, abundance at summering ranges, and the associated vulnerability and variability of these populations, is a shortfall in agency grizzly bear conservation strategies. Therefore, the objectives of our study were to assess the natal origin of moths collected from two mountain ranges and within the Great Plains, characterize larval feeding habits of migrants collected from the Absaroka Range, and assess a monitoring protocol to determine moth abundance at a GYE aggregation site. Using stable isotopes, we estimated the natal origin of migrants collected from the Absaroka and Lewis Ranges, examined migratory patterns within the Great Plains, and assessed the larval feeding habits of migrants collected in the Absaroka Range during 2017-2021. To estimate abundance, we sampled the airspace with a radar stationed within 1 km of an aggregation site in the GYE during 2020 and 2021. There was strong evidence that moths collected in the Great Plains and both mountain ranges were migrating north-south, in addition to previously established east-west movement. Although their origins were varied, moths of the Absaroka Range had the highest probability of origin in Alberta and British Columbia, and moderate probability in Montana, Idaho, and Wyoming across all collection years. Lewis Range moths had the highest probability of origin almost exclusively within the lower third of Canada. As larvae, the moths collected from the Absaroka Range fed almost exclusively on C3 plants. We estimate that 5 million moths passed through our radar's sampling plane (160-750 m above ground level and 2600 m across) over the course of 20 hours (5 nights of movement). Overall, our findings suggest that army cutworm moths at aggregation sites are 'supplied' by various source locations, and thus insulated against regional declines within their natal origins. Radar should be used at moth aggregation sites to continue monitoring army cutworm moths.Item Two grizzly bear studies : moth feeding ecology and male reproductive biology(Montana State University - Bozeman, College of Letters & Science, 1996) White, Donnell DeeItem A study of the climatic conditions favoring the abundance of groups of cutworm moths (Phalaenidae)(Montana State University - Bozeman, College of Agriculture, 1928) Tinkham, Ernest R.