Browsing by Author "Lowrey, Blake"

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Heterogeneity in risk‐sensitive allocation of somatic reserves in a long‐lived mammal
(Wiley, 2022-07) Smiley, Rachel A.; Wagler, Brittany L.; LaSharr, Tayler N.; Denryter, Kristin A.; Stephenson, Thomas R.; Courtemanch, Alyson B.; Mong, Tony W.; Lutz, Daryl; McWhirter, Doug; Brimeyer, Doug; Hnilicka, Patrick; Lowrey, Blake; Monteith, Kevin L.
Food quality and availability, when combined with energetic demands in seasonal environments, shape resource acquisition and allocation by animals and hold consequences for life-history strategies. In long-lived species with extensive maternal care, regulation of somatic reserves of energy and protein can occur in a risk-sensitive manner, wherein resources are preferentially allocated to support survival at the cost of investment in reproduction. We investigated how Rocky Mountain bighorn sheep (Ovis canadensis), an alpine mammal in a highly seasonal environment, allocates somatic reserves across seasons. In accordance with the hypothesis of risk-sensitive resource allocation, we expected accretion and catabolism of somatic reserves to be regulated relative to preseason nutritional state, reproductive state, and variation among populations in accordance with local environmental conditions. To test that hypothesis, we monitored seasonal changes in percent ingesta-free body fat (IFBFat) and ingesta-free, fat-free body mass (IFFFBMass) in three populations of bighorn sheep in northwest Wyoming between 2015 and 2019 through repeated captures of female sheep in December and March of each year in a longitudinal study design. Regulation of somatic reserves was risk-sensitive and varied relative to the amount of somatic reserves an animal had at the beginning of the season. Regulation of fat reserves was sensitive to reproductive state and differed by population, particularly over the summer. In one population with low rates of recruitment of young, sheep that recruited offspring lost fat over the summer in contrast to the other two populations where sheep that recruited gained fat. And yet, all populations exhibited similar changes in fat catabolism and risk sensitivity over winter. The magnitude of body fat and mass change across seasons may be indicative of sufficiency of seasonal ranges to meet energetic demands of survival and reproduction. Risk-sensitive allocation of resources was pervasive, suggesting nutritional underpinnings are foundational to behavior, vital rates, and, ultimately, population dynamics. For species living in alpine environments, risk-sensitive resource allocation may be essential to balance investment in reproduction with ensuring survival.
Niche similarities among introduced and native mountain ungulates
(2018-07) Lowrey, Blake; Garrott, Robert A.; McWhirter, Douglas E.; White, Patrick J.; DeCesare, N. J.; Stewart, Shawn T.
The niche concept provides a strong foundation for theoretical and applied research among a broad range of disciplines. When two ecologically similar species are sympatric, theory predicts they will occupy distinct ecological niches to reduce competition. Capitalizing on the increasing availability of spatial data, we built from single species habitat suitability models to a multispecies evaluation of the niche partitioning hypothesis with sympatric mountain ungulates - native bighorn sheep (BHS; Ovis canadensis) and introduced mountain goats (MTG; Oreamnos americanus) in the northeast Greater Yellowstone Area. We characterized seasonal niches using two-stage resource selection functions with a used-available design and descriptive summaries of the niche attributes associated with used GPS locations. We evaluated seasonal similarity in niche space according to confidence interval overlap of model coefficients and similarity in geographic space by comparing model predicted values with Schoener\'s D metric. Our sample contained 37,962 summer locations from 53 individuals (BHS = 31, MTG = 22), and 79,984 winter locations from 57 individuals (BHS = 35, MTG = 22). Slope was the most influential niche component for both species and seasons, and showed the strongest evidence of niche partitioning. Bighorn sheep occurred on steeper slopes than mountain goats in summer and mountain goats occurred on steeper slopes in winter. The pattern of differential selection among species was less prevalent for the remaining covariates, indicating similarity in niche space. Model predictions in geographic space showed broad seasonal similarity (summer D = 0.88, winter D = 0.87), as did niche characterizations from used GPS locations. The striking similarities in seasonal niches suggest that introduced mountain goats will continue to increase their spatial overlap with native bighorn. Our results suggest that reducing densities of mountain goats in hunted areas where they are sympatric with bighorn sheep and impeding their expansion may reduce the possibility of competition and disease transfer.Additional studies that specifically investigate partitioning at finer scales and along dietary or temporal niche axes will help to inform an adaptive management approach.
Restoration Potential of Bighorn Sheep in a Prairie Region
(2020-07) DeVoe, Jesse D.; Lowrey, Blake; Proffitt, Kelly M.; Garrott, Robert A.
Efforts to recover Rocky Mountain bighorn sheep (Ovis canadensis canadensis) throughout western North America have had limited success with the majority of current populations remaining in small and isolated areas on a fraction of their historical range. Prairie environments with rugged topography throughout the Northern Great Plains ecoregion were historically occupied by relatively robust bighorn sheep populations. We predicted there is likely unrealized potential habitat for restoring bighorn sheep to these areas; however, relatively little attention has been devoted to identifying habitat in unoccupied prairie regions. We used global positioning system (GPS)-collar data collected from 43 female bighorn sheep in 2 populations located in the eastern Montana, USA, portion of the Northern Great Plains during 2014–2018 to estimate a population-level annual resource selection model and identify the important factors affecting bighorn sheep resource selection. We extrapolated model predictions across eastern Montana's prairie region and identified potential habitat to understand restoration potential and assist with future translocations of bighorn sheep. Resource selection of bighorn sheep was most strongly associated with terrain slope and ruggedness, tree canopy cover, and a normalized difference vegetation index metric. Within currently unoccupied areas of the historical range, the model extrapolation predicted 7,211 km2 of habitat, with most owned and managed by private landowners (44%), Bureau of Land Management (33%), and the United States Fish and Wildlife Service (15%). Our results provide an empirical evaluation of landscape covariates influencing resource selection of bighorn sheep occupying prairie environments and provide a habitat model that may be generalizable to other areas in the Northern Great Plains ecoregion. We demonstrate substantial potential for restoration opportunities of bighorn sheep in the Northern Great Plains ecoregion. Broad restoration of bighorn sheep across the ecoregion would likely require strong collaboration among and between public resource managers, private landowners, and livestock producers given the heterogeneous land ownership patterns, management strategies, and domestic sheep distributions.
Seasonal resource selection by introduced mountain goats in the southwest Greater Yellowstone Area
(2017-04) Lowrey, Blake; Garrott, Robert A.; Miyasaki, Hollie M.; Fralick, Gary L.; Dewey, Sarah R.
Mountain goats (Oreamnos americanus) are among the least studied North American ungulates. Aided by successful translocations from the early to mid-1900s, introduced populations have greatly expanded within non-native ranges, yet there remains a paucity of empirical studies concerning their habitat requirements and potential distributions. The lack of studies presents a formidable challenge to managers tasked with monitoring mountain goat expansion and mitigating for any potential negative impacts posed to native species and communities. We constructed summer and winter resource selection models using GPS data collected during 2011-2014 from 18 (14 female and four male) mountain goats in the Snake River Range of the southwest Greater Yellowstone Area. We used generalized linear mixed models and evaluated landscape and environmental covariates at multiple spatial grains (i.e., neighborhood analyses within 30-, 100-, 500-, and 1000-m buffers) within four related suites. The multi-grain resource selection function greatly improved model fit, indicating that mountain goat resource selection was grain dependent in both seasons. In summer, mountain goats largely selected rugged and steep areas at high elevations and avoided high solar radiation, canopy cover, and time-integrated normalized difference vegetation index (NDVI). In winter, mountain goats selected lower elevations characterized by steep and rugged slopes on warm aspects and avoided areas with high canopy cover, NDVI amplitude, and snow water equivalent. Slope was the dominant predictor of habitat use in both seasons, although mountain goats selected for steeper slopes in winter than in summer. Regional extrapolations depicted suitable mountain goat habitat in the Snake River, Teton, Gros Ventre, Wyoming, and Salt Ranges centered around steep and rugged areas. Winter range was generally characterized by the steepest slopes within a more broadly distributed and generally less steep summer range. Further research should examine the spatial and temporal overlap with native populations to further our understanding of resource selection dynamics and the potential for introduced mountain goats to alter intraguild behavioral processes of sympatric species, namely the Rocky Mountain bighorn sheep (Ovis canadensis canadensis).
A Survey of Bacterial Respiratory Pathogens in Native and Introduced Mountain Goats ( Oreamnos americanus)
(2018-06) Lowrey, Blake; Butler, Carson J.; Edwards, William H.; Wood, Mary E.; Dewey, Sarah R.; Fralick, Gary L.; Jennings-Gaines, Jessica E.; Killion, Halcyon J.; McWhirter, Douglas E.; Miyasaki, Hollie M.; Stewart, Shawn T.; White, Kevin S.; White, Patrick J.; Garrott, Robert A.
In contrast to broad range expansion through translocations, many mountain goat ( Oreamnos americanus) populations have shown signs of decline. Recent documentation of pneumonia in mountain goats highlights their susceptibility to bacterial pathogens typically associated with bighorn sheep ( Ovis canadensis) epizootics. Respiratory pathogen communities of mountain goats are poorly characterized yet have important implications for management and conservation of both species. We characterized resident pathogen communities across a range of mountain goat populations as an initial step to inform management efforts. Between 2010 and 2017, we sampled 98 individuals within three regions of the Greater Yellowstone Area (GYA), with a smaller sampling effort in southeast Alaska, USA. Within the GYA, we detected Mycoplasma ovipneumoniae in two regions and we found at least two Pasteurellaceae species in animals from all regions. Mannheimia haemolytica was the only pathogen that we detected in southeast Alaska. Given the difficult sampling conditions, limited sample size, and imperfect detection, our failure to detect specific pathogens should be interpreted with caution. Nonetheless, respiratory pathogens within the GYA may be an important, yet underappreciated, cause of mountain goat mortality. Moreover, because of the strong niche overlap of bighorn sheep and mountain goats, interspecific transmission is an important concern for managers restoring or introducing mountain ungulates within sympatric ranges.