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Fatal attraction for an imperiled songbird: is cropland in the northern Great Plains an ecological trap for breeding thick-billed longspur?
(Montana State University - Bozeman, College of Agriculture, 2022) Swicegood, Amber Elizabeth; Chairperson, Graduate Committee: Lance McNew
Thick-billed longspur (Rhynchophanes mccownii) populations have declined 4% annually during the past 50 years. This species nests in recently disturbed or sparsely vegetated patches within native mixed-grass prairie and is also known to occur in crop fields in northeastern Montana during the breeding season. Maladaptive habitat selection may result in crop fields operating as ecological traps, but information on thick-billed longspur use of and demography in crop fields are lacking. We hypothesized that crop fields provide cues for territory selection, but frequent human disturbance and increased exposure to weather and predators should result in reduced reproductive success relative to native grassland habitats. To address this hypothesis, we 1) used dynamic occupancy models to compare arrival times of territorial male longspurs using data collected with autonomous acoustic recorders, 2) used open population distance sampling models to compare trends in longspur abundance over the breeding season, 3) compared indices of nest density and number of young fledged, and 4) used nest survival models to compare survival rates of nests between crop and native sites. Arrival times were similar in both site types and occupancy ranged from 0.52 + or - 0.17SE on April 7 to 0.99 + or - 0.01 on April 30. Bird abundances appeared to be mediated by vegetation biomass and drought conditions. Standardized nest densities were 0.15 + or - 0.22SD and 0.23 + or - 0.32 nests/hour/plot in crop and native sites, respectively; the number of young fledged per successful nest was similar in crop and native sites and averaged 2.9 + or - 0.18SE. Nest survival was similar in crop and native sites and averaged 0.24 + or - 0.03 SE (n=222 nests). The data did not support our ecological trap hypothesis: longspurs did not exhibit a clear preference for crop sites and reproductive output was not significantly reduced. Our results suggest that crop fields may expand nesting opportunities for thick-billed longspur in a region where native habitat may be limited.
Carry-over effects in partially migratory greater sage-grouse, southwest Montana
(Montana State University - Bozeman, College of Letters & Science, 2022) Waxe, James Andrew; Chairperson, Graduate Committee: Andrea Litt; This is a manuscript style paper that includes co-authored chapters.
Migration is a common natural phenomenon and an important life history strategy for many animal species. Migration allows individuals to accommodate changing environmental conditions, with the potential to increase survival or future reproduction. Many migratory species are subject to carry-over effects, where conditions experienced during one season or life stage influence subsequent life stages. Previous research has largely focused on evaluating the influence of carry-over effects on long-distance migrants, but less is known about these influences on shorter-distance migrants. During research in southwest Montana and southeast Idaho, we used VHF radio collars, red blood cells, stable isotopes, and morphometric information to understand the influence of carry-over effects on Greater Sage-grouse. In this population, some individuals migrate only short distances, while others may not migrate at all. We evaluated the influence of 1) different migration strategies and breeding locations on the body condition of females before breeding and 2) how variation in pre-breeding body condition influenced subsequent reproduction. We found non-migratory individuals were in better pre- breeding body condition than migrants during years with less winter precipitation. Similarly, individuals who experienced less precipitation during the breeding season also had higher pre- breeding body condition. Pre-breeding body condition positively influenced offspring weight early in the breeding season, but this relationship was less apparent later in the season. Our data suggest carry-over effects occur in this population of sage-grouse, but the magnitude of these effects was largely dependent on environmental conditions and timing of breeding. With increasing evidence of carry-over effects in sage-grouse populations, managers should broaden their conservation strategies to account for all life stages. Protecting a variety of winter habitat both near and distant from breeding areas will ensure the persistence and reproductive contribution of individuals with different migration strategies. Furthermore, protecting all known sage-grouse leks provides variation within a single population which allows for flexibility to respond in changing environments. Maintaining or enhancing landscape-level habitat heterogeneity supports variable life-history strategies and is critical for sage-grouse conservation.
Variation of life-history strategies in pinnipeds with an emphasis on survival rates and spatial distribution of male Weddell seals in Erebus Bay, Antartica
(Montana State University - Bozeman, College of Letters & Science, 2020) Brusa, Jamie Louise; Chairperson, Graduate Committee: Jay J. Rotella; Jay J. Rotella, Robert A. Garrott, J. Terrill Paterson and William A. Link were co-authors of the article, 'Variation of annual apparent survival and detection rates with age, year, and individual identitiy in male Weddell seal (Leptonychotes weddellii) from long-term mark-recapture data' in the journal 'Population ecology' which is contained within this dissertation.; Jay J. Rotella, Katharine M. Banner and Patrick R. Hutchins were co-authors of the article, 'A comparative study evaluating how stage-specific survival rates vary with life-history traits in male pinnipeds' submitted to the journal 'Journal of evolutionary biology' which is contained within this dissertation.; Jay J. Rotella was a co-author of the article, 'Influence of age and individual identity in the use of breeding colony habitat by male Weddell seals (Leptonychotes weddellii) in Erebus Bay, Antarctica' submitted to the journal 'Journal of mammalogy' which is contained within this dissertation.
This dissertation explores various components of male life-history theory using a species-specific approach focusing on Weddell seals (chapters 2 and 4) and a comparative approach focusing on pinniped (seal and sea lion) species (chapter 3). To better understand how marine mammal populations can function and to gain insight about the evolution of male Weddell seal fitness, my coauthors and I estimated the age-specific survival rates of male Weddell seals living in Erebus Bay, Antarctica. Actuarial senescence (decreasing age-specific survival with increasing age) has been documented for several wildlife species. However, contrary to females, little information exists regarding age-specific patterns of survival, including actuarial senescence, for males. We used 35 years of mark-recapture data to estimate age-specific survival rates in male Weddell seals using a hierarchical model approach in a Bayesian framework. We found that male survival estimates were moderate for pups and yearlings, highest for 2-yearolds, and gradually declined with age thereafter such that the oldest animals observed had the lowest survival rates of any age, illustrating that male Weddell seals in this population exhibit actuarial senescence. We further investigated male Weddell seal ecology by describing the spatial patterns of male Weddell seals in Erebus Bay using regression modeling and kernel density methods. The intermediately aged males tended to have the most reproductive-age female neighbors, but individual heterogeneity played a stronger role than age. We found that younger males tended to settle in more offshore and less crowded areas of the habitat relative to older males. From a comparative approach, we assessed the patterns of tradeoffs among various fitness traits in male pinnipeds by examining the relationships between stage-specific survival rates and body size, baculum size, mating strategies, and delayed social maturity. Comparative studies similar to ours have tended to focus on females of avian and some terrestrial species and have mostly addressed reproductive traits. However, we lack information about males and connections between survival rates and other life-history traits. We found evidence for a relationship between precopulatory, rather than postcopulatory, traits and survival rates. We highlight the need for more empirical survival rate data and robust comparative methods.
Breeding ecology of greater sage-grouse in southwestern Montana
(Montana State University - Bozeman, College of Agriculture, 2021) Cutting, Kyle Anthony; Chairperson, Graduate Committee: Jay J. Rotella and Bok Sowell (co-chair); Jay J. Rotella, Sean R. Schroff, Michael R. Frisina, James A. Waxe, Erika Nunlist and Bok F. Sowell were co-authors of the article, 'Maladaptive nest-site selection by a sagebrush dependent species in a grazing-modified landscape' in the journal 'Journal of environmental management' which is contained within this dissertation.; Jay J. Rotella, Emma Grusing, James A. Waxe, Erika Nunlist and Bok F. Sowell were co-authors of the article, 'Nutrient sources for offspring formation: diet-mother and mother-offspring isotopic discrimination in domesticated gallinaceous birds' submitted to the journal 'Isotopes in environmental and health studies' which is contained within this dissertation.; Jay J. Rotella, James A. Waxe, Aaron O' Harra, Sean R. Schroff, Lorelle Berkeley, Mark Szczypinski, Andrea R. Litt, Bok F. Sowell were co-authors of the article, 'Resource allocation effects on the timing of reproduction in an avian habitat specialist' in the journal 'Ecosphere' which is contained within this dissertation.
The greater sage-grouse (Centrocercus urophasianus; hereafter: sage-grouse) is an umbrella species that needs large intact tracts of sagebrush habitat with habitat requirements that represent the needs of many other species found in the sagebrush biome of the American West. Much of the information collected to date on sage-grouse is from low-elevation, homogenous, landscapes, leaving information gaps for topographically complex, high elevation locations within the sage-grouse range. In this dissertation, I assess the following aspects of the breeding ecology of sage-grouse: 1) how females select nest and brood sites based on sagebrush type, along with livestock grazing features and other biotic and abiotic characteristics; 2) the influence of female nest-site selection on nest-survival outcomes; 3) experimentally derived isotopic discrimination values in domesticated gallinaceous birds as an estimation method for nutrient allocation strategies in wild sage-grouse; and 4) the degree to which females allocated nutrients from winter habitats for formation of offspring by comparing females nesting in southwest vs. central Montana. Based on the research, I found evidence that: 1) sage-grouse avoid a high-elevation sagebrush type that is the most common type in my study region and instead select for intermediate- or low-elevation sagebrush types for both nesting and brood rearing, 2) sage-grouse broods selected sites away from low-lying mesic areas and near ridgelines on upper slopes with south-facing aspects and sites further from cattle paths, 3) nest survival was (a) higher for nests placed away from fence lines, (b) lower in areas with more cow pies and taller dead grass, and (c) higher in areas with increased living grass cover, and 4) females from southwest Montana and in the high-elevation sagebrush type primarily allocated nutrients from winter habitats, whereas females from central Montana and in the low-elevation sagebrush type primarily allocated nutrient sources from spring habitats for offspring formation. My findings highlight a unique breeding strategy for sage-grouse residing in high-elevation sagebrush landscapes. Results described herein will allow managers in southwest Montana, and other regions in the northern Rocky Mountains, to better manage sage-grouse and sage-grouse habitats.
Wolverine habitat quality, connectivity, and prioritization at the landscape scale
(Montana State University - Bozeman, College of Letters & Science, 2019) Carroll, Kathleen Anne; Chairperson, Graduate Committee: Andrew J. Hansen; Andrew J. Hansen, Robert M. Inman and Rick L. Lawrence were co-authors of the article, 'Comparing methods to disentangle habitat predictors for wolverines in the southern extent of their distribution' which is contained within this dissertation.; Andrew J. Hansen, Robert M. Inman, Rick L. Lawrence and Andrew B. Hoegh were co-authors of the article, 'Testing landscape resistance layers and modeling connectivity for wolverines in the western US' which is contained within this dissertation.; Robert M. Inman, Andrew J. Hansen, Kevin Barnett and Rick L. Lawrence were co-authors of the article, 'Prioritizing metapopulation connectivity for wolverines' which is contained within this dissertation.
The core of conservation biology is understanding how to mitigate the impacts of anthropogenic activities on species. These impacts are particularly detrimental to isolated and small populations, which face extirpation or extinction without immediate conservation action. For small and isolated populations, protecting connective habitat (e.g., corridors) and facilitating movement is key. Corridor identification requires rigorous planning and appropriate statistical choices to ensure that resulting conservation actions are defensible and best support ecological processes. This manuscript asks: 1) how do different, commonly used statistical methods inform our understanding of species resource selection across scale and between sexes, 2) how does landscape resistance and connectivity differ between resident and dispersing individuals, and 3) what information is important to include in a systematic conservation plan to best support on-the-ground conservation between land trusts, landowners, and other practitioners under future climate change conditions. To address each of these questions we focused on wolverines (Gulo gulo), which exist as isolated metapopulations across the western contiguous United States. Our key findings included that 1) the importance of habitat variables differ only slightly by sex, across selection scales, and across analysis methods, 2) dispersing animals are less sensitive to habitat quality compared to resident animals, and 3) including information that both helps mitigate potential threats and preserves ecological processes is the best approach for connectivity conservation planning. This work represents the most comprehensive wolverine connectivity conservation analyses to date. This research suggests that examining multiple approaches and validating results is critical to generating rigorous and defensible conservation decisions are being made for wolverines, although more studies are needed to validate this in other species. Taken together, this research provides land managers, policy makers, and scientists with guidance for future connectivity analyses, conservation action for wolverines, and a research framework that can be applied to additional species of conservation concern in isolated populations.
Characterizing summer roosts of male little brown myotis (Myotis lucifugus) in lodgepole pine-dominated forests
(Montana State University - Bozeman, College of Letters & Science, 2020) Hilty, Shannon Lauree; Chairperson, Graduate Committee: Andrea Litt
Although bat roosts have been well-studied in the eastern United States, we know less about roosts in the west. Western bats may make use of trees and snags, as in the eastern US, but the Rocky Mountains provide more exposed rock, which could contribute to western bat species using different roosting features. Additionally, roost studies often focus on maternity colonies, and information on roosts used by male bats is limited. Given that roosting sites may be limiting, we aimed to quantify structural features of roosts used by male little brown myotis (Myotis lucifugus) in forests dominated by lodgepole pine (Pinus contorta) during the summer and determine whether bats are selecting roosts with particular features disproportionately to what is available on the landscape. We mist-netted for bats during the summers of 2017 and 2018 and attached transmitters to 34 male little brown myotis. We located at least 1 roost for 20 individuals (average = 2.85 roosts/bat, range = 1-6). Although snags were available, most bats roosted in rock features (86% in rocks, 14% in snags); rock roosts were mainly in crevices with vertical orientations (85%) instead of rock cavities (15%). Male bats were more likely to select roosts with less canopy closure (mean for used locations = 14.1%, SE = 2.3) that were closer to water (1063.1 m, SE = 136.2). They also selected roosts with more overall rock cover (77%, SE = 3), wider entrances (3.1 cm, SE = 0.3), and access to a skyward-facing crevice, creating warmer microclimates. Our work indicates that rock features provide essential summer habitat for male little brown myotis and that lodgepole pine in this landscape may not provide appropriate roosting features. Understanding how other bat species may be using rock features, during summer and other seasons, remains a sizeable information gap. Learning more about hibernacula is of great importance due to the spread of white-nose syndrome and rock features may be essential autumn transitional roosts and winter hibernacula at higher elevations. Roosts that provide variation in microclimate, including the potential for passive warming, could be very beneficial for bats recovering from white-nose syndrome.
Assessing alternative drivers of occupancy, abundance, and elevational range retraction at the range core of a climate-sensitive mammal
(Montana State University - Bozeman, College of Letters & Science, 2020) Billman, Peter Donn; Chairperson, Graduate Committee: David McWethy
Ecological niche theory and niche conservativism suggest that rising temperatures globally will continue pressuring species to track cooler environments. Examining changes in occupancy and abundance together across bioclimatic gradients can inform forecasts of expected range shifts. Although occupancy and abundance reflect similar aspects of species-environment relationships, they are governed by different underlying processes. Abundance is thought to be more reflective of shorter-term conditions affecting vital rates, whereas site occupancy often reflects habitat suitability. By directly comparing results of both response types, as well as elevational range retraction, we offer a robust method for assessing complex species-climate relationships. In this study, we test how populations of the American pika (Ochotona princeps), a small montane lagomorph, respond to varying climatic conditions. To do so, we tested and compared the drivers of site occupancy, abundance, and upslope retraction, across 760 talus patches, nested within 64 watersheds across the Northern Rocky Mountains, USA. Using mixed-effects modeling, paired with an information-theoretic approach, we tested model suites that reflected hypothesized species-climate relationships to identify the top models of each of our response classes. Approximately one third (33.9%) of patches were found extirpated. The most important environmental predictors differed among occupancy, abundance, and amount of upslope retraction. For site occupancy, the top model included metrics of summer acute heat stress, actual evapotranspiration, and habitat availability. For abundance, acute heat stress and the preceding winter's mean temperature (i.e. chronic cold stress) was the top-ranked model, suggesting rapid responses of populations to recent climatic conditions. Furthermore, we found that a model including both chronic heat and chronic cold stress best predicted the total amount of vertical retraction across watersheds, whereas acute heat stress and summer precipitation best explained the residuals. Our results emphasize the complexity associated with evaluating species responses to environmental change and that results from occupancy analyses should be used with caution when extrapolating to predicting abundances across varied landscapes. Our method for assessing the drivers of elevational retraction across a suite of watersheds has widespread applications for evaluating species response to changing climatic conditions elsewhere.
Spatial and temporal variability in movements and vital rates of sympatric salmonids in an unfragmented, inland watershed
(Montana State University - Bozeman, College of Letters & Science, 2019) Lance, Michael James; Chairperson, Graduate Committee: Alexander V. Zale
The life history patterns and vital rates of stream dwelling fish can differ across biological, spatial, and temporal scales. We determined the movement patterns and vital rates of three abundant salmonids--brown trout (Salmo trutta), mountain whitefish (Prosopium williamsoni), and rainbow trout (Oncorhynchus mykiss)--in the Smith River watershed of Montana, a system with three distinct geomorphic regions: the headwaters, semi-wilderness canyon, and prairie. We marked 7,172 fish with passive integrated transponder (PIT) tags, monitored their watershed-scale movements past 15 stationary PIT arrays over four years, and relocated fish between arrays by conducting mobile surveys along the Smith River and major tributaries. Fish movement patterns and survival probabilities varied seasonally, among species, and among locations within the watershed. Volume of movement and diversity of movers were both greatest in the canyon region and in lower portions of tributaries. Fish rarely left the canyon, but movement into the canyon from other regions was common among some groups of fish. Mountain whitefish were most likely to move and brown trout were least likely to move. The stream lengths traversed by fish followed a leptokurtic distribution with most fish travelling < 10 km and decreasing numbers of fish travelling farther. Distinct life history patterns were not evident as judged by the stream lengths traversed by tagged fish; rather, a continuous spectrum of distances traversed was apparent. Species-specific spawning periods were associated with increased frequency of movement by mountain whitefish and rainbow trout. Increases in the frequency of watershed-scale movements of all three species were associated mean daily water temperatures of 11.7-15.3°C, compared to periods when water temperatures were cooler or warmer. Annual probabilities of survival were highest among mountain whitefish (0.38-0.54) and lower among brown trout (0.16-0.38) and rainbow trout (0.08-0.39). Survival of rainbow trout and mountain whitefish was highest in the canyon. Survival of mountain whitefish was also high in the headwaters but was lowest in the prairie. Movements of fish in the Smith River watershed were diverse, allowed movement among habitats with different probabilities of survival, and probably contributed to meta-population function, population resiliency, and species diversity.
Snowshoe hare habitat use and silvicultural influences in the Greater Yellowstone Ecosystem
(Montana State University - Bozeman, College of Agriculture, 2019) Kurzen, Mark Daniel; Chairperson, Graduate Committee: Bok Sowell
Snowshoe hares (Lepus americanus) are the main prey base of the Canada lynx (Lynx canadensis) and are an important food source for many forest carnivores. Snowshoe hare research in the Greater Yellowstone Ecosystem is lacking and current research conclusions differ in regards to the types and ages of forests that snowshoe hares prefer. The US Forest Service has implemented limitations and prohibitions on silviculture in this area based on previous snowshoe hare studies. However, some research in the Greater Yellowstone Ecosystem suggests that regenerating lodgepole pine (Pinus contorta) stands that are associated with silviculture benefit snowshoe hares. We implemented three snowshoe hare use indices in southwest Montana within a portion of the Custer-Gallatin National Forest during 1999-2012 to assess snowshoe hare use of forest cover types in Greater Yellowstone Ecosystem. Our study area was located in a designated US Forest Service timber management area where a history of silviculture has resulted in a heterogeneous landscape of multiple successional stages intermingled with other old growth stands. We analyzed 11 years of snowshoe hare pellet plot surveys using linear mixed models and AIC c model selection. Our results suggested that the understory conifer species was the best predictor of use and that the youngest two classes of regenerating lodgepole pine stands had the greatest snowshoe hare use. We analyzed 13 years of snowshoe hare track counts on roads within our study area using Chi-squared goodness-of-fit tests based on proportional road segment lengths and the associated cover types. We observed the greatest snowshoe hare habitat use in the youngest two classes of regenerating lodgepole pine stands. We live-trapped snowshoe hares for one winter in our study area and observed the greatest number of hares captured per night in the youngest lodgepole pine stands. The findings from our 13 year study suggest that snowshoe hare use was greatest in early successional lodgepole pine forests that were approximately 30-60 years old and associated with clear cutting and pre-commercial thinning.
Spatial ecology of mountain ungulates in the northern Rocky Mountains: range expansion, habitat characteristics, niche overlap, and migratory diversity
(Montana State University - Bozeman, College of Letters & Science, 2018) Lowrey, Blake Henson; Chairperson, Graduate Committee: Robert A. Garrott; Robert A. Garrott, Hollie M. Miyasaki, Gary Fralick and Sarah R. Dewey were co-authors of the article, 'Seasonal resource selection by introduced mountain goats in the southwest greater Yellowstone area' in the journal 'Ecosphere' which is contained within this thesis.; Robert A. Garrott, Doug E. McWhirter, P.J. White, Nicholas J. DeCesare and Shawn T. Stewart were co-authors of the article, 'Niche similarities among introduced and native mountain ungulates' in the journal 'Ecological applications' which is contained within this thesis.; Kelly M. Proffitt, Douglas E. McWhirter, P. J. White, Alyson B. Courtemanch, Sarah R. Dewey, Hollie M. Miyasaki, Kevin L. Monteith, Julie S. Mao, Jamin L. Grigg, Carson J. Butler, Ethan S. Lula and Robert A. Garrott were co-authors of the article, 'Contrasting seasonal movements in native and restored populations: a case for conserving migratory portfolios' submitted to the journal 'Journal of applied ecology' which is contained within this thesis.; Douglas E. McWhirter, Kelly M. Proffitt, Alyson B. Courtemanch, Kevin L. Monteith, P. J. White, J. Terrill Paterson, Sarah R. Dewey and Robert A. Garrott were co-authors of the article, 'Individual variation creates diverse portfolios of seasonal movement patterns and ranges in a migratory ungulate' submitted to the journal 'Ecology' which is contained within this thesis.
Mountain ungulates, although recognized as iconic and charismatic wildlife species, are the least studied and understood large mammals in western North America. The paucity of data, specifically concerning spatial ecology, presents a formidable challenge to regional wildlife managers tasked with the responsibility of managing populations with limited empirical studies on which to base decisions. We used GPS data collected from bighorn sheep (Ovis canadensis) and mountain goats (Oreamnos americanus) sampled from multiple populations throughout the northern Rocky Mountains to develop comparative studies characterizing seasonal habitats and potential range expansion of introduced mountain goats, niche overlap with native bighorn sheep, and migratory diversity of restored, augmented, and native bighorn sheep. Slope was the dominant predictor of mountain goat 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. Although bighorn sheep occurred on steeper slopes than mountain goats in summer and mountain goats occurred on steeper slopes in winter, we observed broad niche overlap according to season-species niche models and observed GPS locations where the two species were sympatric. In native bighorn sheep herds, we observed longer migrations on average and significantly more variation among individuals when compared to restored herds. The enhanced individual variation in native herds resulted in diverse portfolios of migratory behaviors and ranges, including newly documented high elevation long-distance migrants, increased switching rates between migratory behaviors, and sub-populations that were diffusely spread across both summer and winter ranges. In contrast, restored herds had limited individual variation, were largely non-migratory, had less switching between years, and were generally concentrated on both summer and winter ranges. In addition to increasing the abundance and distribution of bighorn sheep on the landscape, we suggest there may be value in simultaneously increasing the diversity of seasonal movement strategies, and in so doing, building resilience to future perturbations and disease, and mirroring the movement portfolios observed in native populations of bighorn sheep.

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