Author: Caitlyn Powell Wanner

Publisher:

Published: 2022

Total Pages: 0

ISBN-13:

Winter in temperate zones often represents a period of greatest energetic demand for vertebrate species. Animals respond to seasonal scarcity through behavioral strategies such as migration and selecting specific habitats characteristics to maximize resource acquisition and/or minimize energy expenditures. Migration or differential habitat use in winter can complicate goals of defining and conserving core habitat for species across increasingly fragmented landscapes. Greater sage-grouse (Centrocercus urophasianus, hereafter “sage-grouse”) is a species of conservation concern endemic to sagebrush (Artemisia spp.) steppe whose populations are most threatened by anthropogenic disturbance and concomitant degradation to sagebrush communities. Conservation of sage-grouse habitat is complicated by a partially-migratory annual cycle in most populations. Seasonal ranges (spring, summer/fall, and winter) may be integrated to any degree or non-overlapping. Efforts to conserve core habitat for sage-grouse have focused primarily on breeding ranges, which may not capture the needs of sage-grouse during other seasons, with winter habitat being least protected. Greater understanding of winter habitat requirements is needed to improve conservation for sage-grouse throughout their annual cycle. My thesis focused on multi-scale winter habitat ecology of greater sage-grouse (Centrocercus urophasianus) in the Red Desert of southcentral Wyoming, using GPS location data from winters 2018/2019, 2019/2020, and 2020/2021. My research encompassed a 1) landscape-scale validation of management guidelines for winter concentration areas as the second phase to a state-wide analysis, 2) habitat selection and behavior within home- and population-range scales as influenced by winter weather conditions, and 3) a fine-scale evaluation of microhabitat within home- and population-range scales during winter 2020/2021. My results support consideration of winter habitats in conservation plans for sage-grouse populations in rapidly changing landscapes. In Chapter 1, I conducted a systematic review of literature published in the last 46 years (1977–2022) on sage-grouse winter habitat selection and survival. Out of 32 compiled publications, I found that 59.4% of sage-grouse winter habitat literature was published in the last 10 years (2013–2022) and 53.1% of articles over the last 46 years reported avoidance of anthropogenic disturbance by sage-grouse during winter. The most recent recommendations for defining year-round priority habitat for sage-grouse recommend implementation of resource selection modeling for all seasonal periods. In Chapter 2, my research fulfilled the second phase of a larger effort to answer questions posed by the Wyoming Sage-Grouse Implementation Team, through the Winter Concentration Area Subcommittee, regarding sage-grouse winter habitat selection and response to anthropogenic disturbance. Phase 1 used existing datasets of sage-grouse GPS locations from 6 regions across Wyoming to model winter habitat selection and avoidance patterns of disturbance statewide. Results from Phase I formed the basis for developing recommendations for management of sage-grouse winter concentration areas in Wyoming. The purpose of my research in Chapter 2 was to validate results of Phase I modeling and evaluate if the statewide model accurately described sage-grouse winter habitat selection and anthropogenic avoidance in regions not considered in that modeling effort. I used 44,968 locations from 90 individual adult female grouse identified within winter habitat from winters 2018/2019, 2019/2020, and 2020/2021 in the Southern Red Desert region (my study area) for out-of-sample validation. The intent of my validations was to assess if models generated statewide or from a nearby region (Northern Red Desert) would be more effective in predicting sage-grouse habitat selection patterns in areas with little information. The statewide model better predicted sage-grouse habitat use at within-population scales and the near-region model was more predictive at within-home-range scales. I found some variation between regions and the statewide model but similar trends in environmental characteristics and avoidance of anthropogenic features even at low densities. My results from the Southern Red Desert support the recommendation from Phase 1 that anthropogenic surface disturbance should be limited to low levels (≤ 2.5%) within winter concentration areas to conserve sage-grouse winter habitat. In Chapter 3, my research focused on shifting environmental conditions that influence patterns of sage-grouse winter habitat selection. Sage-grouse are physically well adapted to winter conditions; it’s a common assumption that winter weather has little effect on sage-grouse. However, research results have varied in support of this assumption, with significant die-offs correlated to periods of extreme winter weather. My research used daily winter weather conditions to explain sage-grouse winter behavior and habitat selection. I used sage-grouse GPS locations from the Southern Red Desert over winters 2018/2019 and 2019/2020 and obtained local weather conditions for each winter from SnowModel. SnowModel used available meteorological data, landscape characteristics, and snow physics to predict weather conditions at a 30-m resolution and daily scale. By comparing habitat selection and behavior across fine temporal scales, I found that sage-grouse responded to daily weather conditions by selecting refugia habitat more than altering daily activity levels. My results suggest that, in addition to landscape features, sage-grouse selected home ranges at the population scale for warmer wind chill temperatures and greater windspeed. Within home ranges, sage-grouse appeared to respond to harsher weather (lower wind chill temperature and high wind speeds) by selecting greater sagebrush cover and leeward sides of ridges. Our research underlines the importance of examining winter habitat at narrower temporal scales than the entire winter season to identify important refugia features that may only be used periodically. Additional research into quantifying weather refugia for wintering sage-grouse populations may provide greater insight to the future sustainability of winter ranges. In Appendix A, I compared winter microhabitat characteristics at 90 sage-grouse use sites from the 2019/2020 winter with 90 available sites within the population range and 90 available sites within home ranges. I predicted habitat characteristics at grouse use locations would be more similar to paired random locations within the home range than to random locations within the population range. I also predicted that, because sage-grouse select specific habitat characteristics, there would be fewer differences when comparing random available locations between the home and population range than comparisons of used and available habitat. I found no support for my first prediction and strong support for my second prediction. Sage-grouse dung piles were 7.0- and 9.9-times higher at used locations than random locations within home and population ranges, respectively. Our results suggested that sage-grouse are highly selective for microhabitat. Sage-grouse selected areas with higher big sagebrush (Artemisia spp.) and overall canopy cover, big sagebrush height, and visual obstruction compared to random locations within home and population ranges. Our results indicate concealment cover is important to sage-grouse throughout their annual cycle.