Geology topics

Steven R. Mathews

Publications and source records attributed to Steven R. Mathews.

16 recordsLinked to original sources

USGS2026

Changes in spatial distribution and abundance together determine potential for population persistence for greater sage-grouse

Aim Population ecologists often focus on changes in the distribution and abundance of wildlife species, which are useful for trend analyses and status assessments. However, rarely are these responses evaluated simultaneously for a single species, despite their unique contributions to fully assess a species' viability. For example, focusing solely on total abundance can mask important losses in overall distribution within a metapopulation structure that may contribute to long-term population instability that results from the extirpation of small peripheral populations. Location Bi-State region of Nevada and California, USA. Methods We simultaneously evaluated changes in population abundance and distribution for greater sage-grouse (hereafter sage-grouse; Centrocercus urophasianus ) within the Bi-State Distinct Population Segment (DPS), a genetically distinct and isolated population straddling the border of Nevada and California. We combined population counts, demographic data, and information on space use from marked individuals to evaluate changes in population distribution and abundance over three time periods that corresponded to the three most recent population nadirs (1995–2019, 2002–2019 and 2008–2019). Results The Bi-State DPS exhibited evidence of ~1.2%–2.5% declines annually, over the short/medium-term (1995–2019; λ^ = 0.987, 95% CRI: 0.970–0.999), short-term (2002–2019; λ^ = 0.975, 95% CRI: 0.963–0.985) and recent-term (2008–2019; λ^ = 0.988, 95% CRI: 0.973–1.001). Since 1995, the spatial distribution of sage-grouse abundance in the Bi-State DPS shifted amongst subpopulations, with peripheral subpopulations suffering the largest declines. Main Conclusions Gains in abundance and distribution amongst expanding subpopulations did not offset losses in the remaining subpopulations, with a net loss in occupied distribution of 156 km 2 since 1995. Reductions in spatial distribution could have implications for metapopulation persistence as peripheral populations become more vulnerable to stochastic events, which would not have been apparent from the evaluation of overall metapopulation abundance on its own.

California, Nevada↗

USGS2026

Invasion resistance varies by fuel break type in sagebrush ecosystems

Background Wildfire is an increasingly important driver of changes within sagebrush (Artemisia spp. L.) ecosystems of the western USA, often resulting in increased spread of exotic annual grasses, such as cheatgrass (Bromus tectorum L.), and subsequent losses of native vegetation and wildlife habitat. Fuel breaks— areas of land treated to reduce or redistribute fuel loads — are widely implemented to help prevent the spread of wildfires and provide areas to facilitate firefighting efforts. However, localized installation and maintenance of fuel breaks directly reduce or remove vegetation and may propagate the spread of exotic annual grasses into fuel break boundaries and surrounding areas, inadvertently weakening ecological resilience to disturbance. To investigate if exotic annual grass cover was associated with mowed or green strip fuel breaks across the sagebrush biome, we combined multiple data sources and methodologies. We used targeted field surveys and land-management agency monitoring data within a space-for-time substitution framework coupled with a progressive-change before-after control-impact (PC BACI) study design using historical remotely sensed vegetation cover data which allowed us to account for potential confounding effects of roads on annual grass cover. Results Models using both field collected and remotely sensed vegetation indices estimated increases in exotic annual grass cover over time following mowed fuel break installation, and higher exotic annual grass cover closer to mowed fuel breaks. These increases in exotic annual grass occurred within, at 500 m and at 1000 m from mowed fuel breaks. However, we found variable patterns of exotic annual grass after green strip fuel break installation depending on the data source. No increase in exotic annual grass were indicated by either analysis at distances greater than 500 m from green strip fuel breaks. However, our and field data analyses disagreed on the direction of the association of exotic annual grass cover and green strip fuel breaks. Conclusions Although fuel breaks are an important tool in managing wildland fire, our analysis underscores the importance of planting fire-resistant vegetation, rather than mowing alone, to reduce invasion by annual grasses within and around fuel breaks in sagebrush ecosystems. In addition, site characteristics that hinder the proliferation of exotic annual grasses could be evaluated when installing fuel breaks to minimize unintended effects of exotic annual grass on surrounding sagebrush habitat.

California, Idaho, Nevada, Oregon, Utah↗

USGS2026

Interspecific brood parasitism of a greater sage-grouse brood by chukar in Nevada

Greater sage-grouse ( Centrocercus urophasianus ; hereafter, sage-grouse) populations have declined across their range, resulting in high conservation concerns among state and federal wildlife managers. While interspecific nest parasitism by chukar ( Alectoris chukar ) on sage-grouse nests has been observed previously, the parasitic effects benefiting or harming the reproduction of either species are unknown. Additionally, while chukar eggs have been documented in sage-grouse nests previously, we know of no documented occurrences of chukar chicks parasitizing sage-grouse broods. Here, we report a novel observation of interspecific brood parasitism on a 9-day-old sage-grouse brood by a chukar chick in the Virginia Mountains of northwestern Nevada. Because chukar are an introduced exotic species whose western North American distribution largely overlaps sage-grouse distribution, understanding the dynamics and implications of brood parasitism may inform wildlife management strategies and conservation efforts for sage-grouse throughout their range.

Nevada↗

USGS2025

Conservation translocation immediately reverses decline in imperiled sage-grouse populations

Conservation translocation (hereafter translocation), the intentional movement of organisms from one location to another as a management tool, can be an extremely useful conservation action to increase the abundance of isolated populations following successful habitat restoration. However, managers seek to weigh the benefits against costs to the source population from which individuals are removed. Using two small and imperiled greater sage-grouse ( Centrocercus urophasianus ; hereafter sage-grouse) populations, we demonstrated the usefulness of translocation as a conservation management tool and the value of evaluating the potential consequences of translocation action. Using integrated population models and a before-after-control-impact (BACI) design, we quantified the extent to which translocation influenced the finite rate of change ( λ "> λ ) of apparent abundance ( N "> N ) in both reinforced and source populations. We also assessed changes in underlying demographic rates in one population, allowing for identification of the specific mechanisms causing differences in population trends following translocation. In both reinforced populations, λ ̂ "> λ̂ substantially increased following translocation. In the population for which we had sufficient demographic data, the increase in λ ̂ "> λ̂ resulted from a 179 % increase in egg hatchability following reinforcement. In one translocation, we did not observe adverse effects on the source populations. The source population for the second translocation exhibited reduced population growth rates after translocation, although BACI ratios indicated causes for population declines independent of translocation effects, highlighting the need to investigate processes together with observed patterns. Overall, we demonstrated the ability to rescue isolated sage-grouse populations via translocation, preserving population viability and metapopulation persistence.

California, Montana, Nevada, North Dakota, South D↗

USGS2024

Linking resource selection to population performance spatially to identify species' habitat across broad scales: An example of greater sage-grouse in a distinct population segment

Management decisions often focus on the habitat selection of marked individuals without considering the contribution to demographic performance in selected habitats. Because habitat selection is not always adaptive, understanding the spatial relationship between habitat selection and demographic performance is critical to management decisions. Mapping both habitat selection and demographic performance for species of conservation concern can help guide population-scale conservation efforts. We demonstrate a quantitative approach to differentiate areas supporting selection and survival at large spatial extents. As a case study, we applied this approach to greater sage-grouse ( Centrocercus urophasianus ; hereafter, sage-grouse), an indicator species for sagebrush ecosystems. We evaluated both habitat selection and survival across multiple reproductive life stages (nesting, brood-rearing) in the Bi-State Distinct Population Segment, a genetically distinct and geographically isolated population of sage-grouse on the southwestern edge of the species' range. Our approach allowed us to identify both mismatches between selection and survival and trade-offs between reproductive life stages. These findings suggest resource demands vary across time, with predation risk being a dominant driver of habitat selection during nesting and early brood-rearing periods when chicks are smaller and flightless, whereas access to forage resources becomes more important during late brood rearing when resources become increasingly limited. Moving beyond identifying and managing habitat solely based on species occupancy or use by incorporating demographic measures allows managers to tailor actions to their specific goals; for example, protections of areas that support high selection and high survival and restoration actions focused on increasing survival in areas of high selection and low survival.

California, Nevada↗

USGS2024

Status of greater sage-grouse in the Bi-State Distinct Population Segment—An evaluation of population trends, habitat selection, and efficacy of conservation actions

Preface This study was completed to provide timely scientific information regarding greater sage-grouse population trends, habitat selection, and the efficacy of previous conservation actions implemented to benefit the Bi-State Distinct Population Segment (DPS). Specifically, we provide these analyses to inform the current (2024) status review and pending listing decision for the DPS being undertaken by the U.S. Fish and Wildlife Service. These findings provide updated, detailed, and comprehensive information regarding the status of a geographically isolated and genetically distinct population of a species of high conservation concern and their habitat. Importantly, this report also provides information on the efficacy of previously implemented conservation actions targeting the Bi-State DPS in a framework that is transferable throughout the species’ range.

California, Nevada↗

USGS2023

Geothermal energy production adversely affects a sensitive indicator species within sagebrush ecosystems in western North America

Growing demand for renewable energy has resulted in expansion of energy infrastructure across sagebrush ecosystems of western North America. Geothermal power is an increasingly popular renewable energy source, especially within remote areas, but little is known about the impacts it may have on local wildlife populations. Investigations are warranted given similarities to more conventional surface disturbance activities with well-documented impacts. Using a novel 2-pronged analytical approach, we estimated effects of geothermal energy production activities (hereafter, geothermal) on populations of greater sage-grouse ( Centrocercus urophasianus ; hereafter, sage-grouse), a species of high conservation concern. First, we applied a before-after-control-impact paired series design at two geothermal sites in Nevada, USA, to estimate absence rates of male sage-grouse from lek sites (breeding grounds) and changes in predicted apparent abundance ( λ ̂ "> �̂ ) in relation to geothermal energy infrastructure. We then estimated effects of geothermal energy infrastructure and other environmental covariates on demographic rates. We found λ ̂ "> �̂ declined ∼24 % within 5 km of geothermal sites, while lek absence rates (e.g., indicating local extirpation) increased by ∼730 % within 2 km. Our demographic models revealed decreased nest survival in association with proximity to geothermal infrastructure, reduced topographic impedance surface (TIS; a proxy for sound and light dispersion emanating from geothermal infrastructure), and increased density of common ravens ( Corvus corax ), an effective nest predator. Models also estimated decreases in adult survival in relation to TIS. Finally, we applied population matrix models within a quantitative decision support framework to help guide locations for future geothermal development that balance the need for domestic energy production while minimizing adverse effects on wildlife populations.

Biological Conservation↗

USGS2021

Behavioral state-dependent habitat selection and implications for animal translocations

Post-release monitoring of translocated animals is often used to inform future translocation protocols. Quantifying habitat selection of translocated individuals may help identify features that characterize good settlement habitat and thus inform the choice of future release sites. However, translocated animals often undergo post-release behavioural modification, and their habitat selection may vary depending on the underlying behavioural state. To investigate this, we analysed behavioural state-dependent habitat selection in female greater sage-grouse Centrocercus urophasianus translocated from Wyoming to North Dakota, USA, using Hidden Markov Models combined with Integrated Step Selection Analysis. We segmented individual trajectories into behavioural phases corresponding to an exploratory state, characterized by broad and directed movements, and a restricted state, characterized by short and tortuous movements. Then, we quantified habitat selection in each state while accounting for seasonality and individual reproductive status. While in the exploratory state, sage-grouse exhibited natal habitat preference induction by selecting for high sagebrush cover, which is typical of their natal area in Wyoming but not of the release area in North Dakota. In the restricted state, sage-grouse selected for gentle topography and also adjusted their habitat selection to constraints imposed by seasonality and reproductive needs by selecting for high herbaceous cover during brood rearing. Synthesis and applications . Habitat selection of translocated sage-grouse differed between the post-release exploration and the settlement phase. Features selected after settling, not during exploration, are likely indicative of suitable settlement habitat. Our results suggest that areas characterized by gentle topography and high herbaceous cover are well-suited as release sites for sage-grouse translocated during the summer, especially brood-rearing females, and that sagebrush cover may not be a critical factor in determining the appropriateness of release sites for sage-grouse in North Dakota. Our findings highlight the need to consider behaviour when using habitat selection estimates to inform the choice of future release sites.

North Dakota, Wyoming↗

USGS2021

Offspring of translocated individuals drive the successful reintroduction of Columbian Sharp-tailed Grouse in Nevada, USA

Translocations of North American prairie-grouse (genus Tympanuchus ) present a conservation paradox wherein they are performed to augment, restore, or reintroduce populations, but translocated individuals exhibit a diminished ability to contribute to population restoration. For reintroduced populations without immigration, persistence can only be achieved through reproductive contributions by translocated individuals and their progeny. Due to the disruptive nature of translocation (e.g., physiological chronic stress), progeny produced at restoration sites may outperform founder populations in terms of demographics, but this hypothesis has yet to be tested. We reintroduced Columbian Sharp-tailed Grouse ( T. phasianellus columbianus ; CSTG) to north central Nevada from 2013 to 2017 and used integrated population models (IPMs) to evaluate the process of population establishment and estimate latent contributions of progeny hatched at the restoration site to population rate of change ( ⁠ λ ^ "> λ ^ ⁠ ). Specifically, we used annual lek (i.e. communal breeding arenas) counts and demographic data from translocated individuals to build two separate IPMs to estimate λ ^ "> λ ^ ⁠ . While keeping demographic contributions by translocated individuals identical between models, one IPM assumed local progeny performance was demographically similar to translocated individuals (i.e. the baseline-IPM), and the second assumed that local progeny performed demographically similar to non-translocated CSTG (i.e. the informative-IPM). The baseline-IPM predicted strong population declines following the conclusion of translocations and extirpation by 2020, and it failed to predict observed lek counts. Conversely, the informative-IPM predicted population growth rates ( ⁠ λ ^ "> λ ^ = 1.17, 95% credible interval [CI]: 0.74–1.50) that were more similar to field observations. Offspring of translocated individuals likely perform at similar levels to non-translocated populations, and by not accounting for demographic differences between translocated individuals and non-translocated progeny hatched at the restoration site, managers could underestimate population performance and persistence. Thus, translocation practices that maximize the number of offspring immediately recruited into restoration sites are likely to be the most successful.

Nevada↗

USGS2021

Individual variation in temporal dynamics of post-release habitat selection

Translocated animals undergo a phase of behavioral adjustment after being released in a novel environment, initially prioritizing exploration and gradually shifting toward resource exploitation. This transition has been termed post-release behavioral modification. Post-release behavioral modification may also manifest as changes in habitat selection through time, and these temporal dynamics may differ between individuals. We aimed to evaluate how post-release behavioral modification is reflected in temporal dynamics of habitat selection and its variability across individuals using a population of translocated female greater sage-grouse as a case study. Sage-grouse were translocated from Wyoming to North Dakota (USA) during the summers of 2018–2020. We analyzed individual habitat selection as a function of sagebrush cover, herbaceous cover, slope, and distance to roads. Herbaceous cover is a key foraging resource for sage-grouse during summer; thus, we expected a shift from exploration to exploitation to manifest as temporally-varying selection for herbaceous cover. For each individual sage-grouse ( N = 26), we tested two competing models: a null model with no time-dependence and a model with time-dependent selection for herbaceous cover. We performed model selection at the individual level using an information-theoretic approach. Time-dependence was supported for five individuals, unsupported for seven, and the two models were indistinguishable based on AIC c for the remaining fourteen. We found no association between the top-ranked model and individual reproductive status (brood-rearing or not). We showed that temporal dynamics of post-release habitat selection may emerge in some individuals but not in others, and that failing to account for time-dependence may hinder the detection of steady-state habitat selection patterns. These findings demonstrate the need to consider both temporal dynamics and individual variability in habitat selection when conducting post-release monitoring to inform translocation protocols.

Frontiers in Conservation Science↗

USGS2021

Field methods for translocating female greater sage-grouse (Centrocercus urophasianus) with their broods

Greater sage-grouse ( Centrocercus urophasianus ) have experienced considerable range contraction and reduced abundance in response to habitat loss and degradation. Translocation is a conservation action that is often used to reintroduce extirpated populations or augment existing small populations. Translocations have had limited success in restoring viable populations of sage-grouse; a lack of success is attributed to long-distance post-release movements away from release sites, reduced survival, and lack of reproductive success of translocated individuals. Translocating female sage-grouse with their chicks (brood translocation) is a technique aimed at promoting breeding area fidelity and reproduction and may be beneficial to population restoration efforts. Furthermore, the ability to capture, relocate, and release individuals while minimizing translocation-induced loss increases the overall probability of restoration success. Accordingly, we developed a protocol to translocate female sage-grouse and their broods simultaneously, using a delayed-release system that included a custom release box and acclimation pen. We tested our protocol across 2 separate restoration projects in North Dakota and California during 2017–2019 with a total of 38 translocated females and 196 chicks. We successfully released 174/196 chicks (88.8%) from 32/38 (84.2%) broods. Our protocol builds on existing translocation methods used to translocate sage-grouse and will likely prove to be a critical technique in restoring sage-grouse populations.

California, North Dakota, Wyoming↗

USGS2021

Efficacy of manipulating reproduction of common ravens to conserve sensitive prey species: Three case studies

Expansion of human enterprise across western North America has resulted in an increase in availability of anthropogenic resource subsidies for generalist species. This has led to increases in generalists’ population numbers across landscapes that were previously less suitable for their current demographic rates. Of particular concern are growing populations of common ravens ( Corvus corax ; ravens), because predation by ravens is linked to population declines of sensitive species. Ecosystem managers seek management options for mitigating the adverse effects of raven predation where unsustainable predator–prey conflicts exist. We present 3 case studies examining how manipulating reproductive success of ravens influences demographic rates of 2 sensitive prey species. Two case studies examine impacts of removing raven nests or oiling raven eggs on nest survival of greater sage-grouse ( Centrocercus urophasianus ; sage-grouse) within Wyoming and the Great Basin of California and Nevada, USA, respectively. The third case study uses Mojave desert tortoise ( Gopherus agassizii ; tortoise) decoys to examine effects of oiling raven eggs on depredation rates of juvenile tortoises in the Mojave Desert in California. Initial trial years from all 3 case studies were consistent in finding improved vital rates associated with the application of strategies for reducing reproductive success of ravens. Specifically, removal of raven nests resulted in increased nest survival of sage-grouse within treatment areas where predation by ravens was the primary cause of nest failure. In addition, nest survival of sage-grouse and survival of juvenile tortoise decoys was higher following a treatment of oiling the eggs of ravens in their nests at 2 sites within the Great Basin and 4 tortoise conservation areas in the Mojave Desert in California. Along with specialized technologies that can make techniques such as egg-oiling more feasible, these findings support these management practices as important tools for managing ravens, especially in areas where breeding ravens have negative impacts on sensitive prey species.

California, Nevada, Wyoming↗

USGS2020

Population and habitat analyses for greater sage-grouse (Centrocercus urophasianus) in the bi-state distinct population segment—2018 update

Executive Summary The Bi-State Distinct Population Segment (Bi-State DPS) of greater sage-grouse ( Centrocercus urophasianus , hereinafter “sage-grouse”) represents a genetically distinct and geographically isolated population that straddles the border between Nevada and California. The primary threat to these sage-grouse populations is the expansion of single-leaf pinyon ( Pinus monophylla ) and Utah juniper ( Juniperus osteosperma ) into sagebrush ecosystems, which fragments and reduces population connectivity and survival. Other important threats include low water availability during brood-rearing, particularly during drought, and increased predation by common ravens ( Corvus corax ), a generalist predator often associated with anthropogenic resource subsidies. Although the Bi-State DPS occurs at high elevations relative to sage-grouse range-wide, changes in historical wildfire cycles and the conversion of native shrubs to invasive annual grasslands still threaten these populations. The Bi-State DPS has undergone multiple federal status assessments and associated litigation. For example, in October of 2013, the Bi-State DPS was proposed for listing as threatened under the Endangered Species Act of 1973 by the U.S. Fish and Wildlife Service (USFWS), then withdrawn in April 2015. The withdrawal decision was challenged, and in May 2018, a Federal district court ordered the withdrawal decision to be vacated, and USFWS was required to re-open the October 2013 listing evaluation. In response, the U.S. Geological Survey (USGS), with State and Federal collaborators, embarked on a multipronged analysis to provide current and best available science regarding population status of sage-grouse within the Bi-State DPS. Using data from a long-term monitoring program, we carried out four analytical study objectives, and here, we provide preliminary results of these analyses. First, we used integrated population modeling (IPM) to predict annual population abundance and annual finite rate of population change for the Bi-State DPS, as a whole, and for each subpopulation between 1995 and 2018. Because sage-grouse exhibit population cycles (periodic increases and decreases in abundance across approximately 6- to 10-year wavelengths), we estimated trends across three nested temporal scales that represent one (11 years), two (18 years), and three (24 years) complete population cycles. These estimates of relatively long-term averaged population change account for temporal (that is, interannual) variation. Our model predicted population abundance for the Bi-State DPS during 2018 at 3,305 individuals (2,247–4,683), with the majority occupying Bodie Hills and Long Valley. The model also predicted cyclic dynamics in abundance through time with evidence of 24-year population growth and slight trends of decline over the past 18 years. Specifically, across the Bi-State DPS as a whole, we estimated annual average at 0.99, 0.99, and 1.02 over the one, two, and three population cycles, which equated to a 10.5 percent, 16.6 percent decrease, and 60.0 percent increase in abundance over the 11-, 18-, and 24-year cycles. Estimated abundance in 2018 had not reached numbers lower than those predicted during 1995. However, we found spatial variation in population trends across the three cycles. Bodie Hills subpopulation comprised the greatest (1,521) and exhibited average annual greater than 1.0 across all periods resulting in average annual increases of 7 percent. This relatively large subpopulation has grown 5 times larger than what was predicted in 1995 while experiencing cyclical dynamics within that period. Conversely, other smaller subpopulations within the Bi-State DPS exhibited average annual equal to or less than 1.0 resulting in estimated 10-year risks of extirpation ranging from 2.0 to 76.1 percent. In general, evidence of decline among smaller subpopulations was greatest for the most recent period (2008–18) compared to a period that encompassed three full population cycles (24-year). This difference coincides with an intense period of drought that began in 2012. For comparative purposes as part of this first objective, we conducted a similar analysis for populations of sage-grouse within Nevada and California but outside the Bi-State DPS. We developed a region-wide and distance-weighted IPM using lek count from Nevada Department of Wildlife (NDOW) and California Department of Fish and Wildlife (CDFW) databases and with telemetry data collected by USGS across 12 sage-grouse subpopulations. Our models predicted similar patterns in population cycling outside the Bi-State DPS but with much stronger evidence of long-term declines across 24 years. Specifically, median averaged across each year of the 11-, 18-, and 24-year periods resulted in average annual values of 0.94, 0.97, and 0.99, respectively. These values equate to 41.0 percent, 38.5 percent, and 21.3 percent declines over the corresponding periods. Second, we used lek count data in a state-space modeling framework to compare trends in population abundance across different spatial scales (that is, leks versus Bi-State DPS). This hierarchical framework allowed us to disentangle declines associated with climate conditions as opposed to other local level factors that might signal the need for management intervention. Specifically, we identified 7 leks that were both declining and recently decoupled from larger spatial scale trends, typically governed by climatic conditions (referred to as soft or hard signals). The goal of this analysis was to provide an early warning system that might have implications for conservation actions at local scales. Third, we developed phenological (spring, summer–fall, and winter) and reproductive life stage (nesting, early brood-rearing, and late-brood rearing) based resource selection functions using various environmental covariates. We report rankings of variable importance for each season and life stage, developed maps of habitat selection indices (HSI), binned categories representing low, moderate, and high classes of quality (where any category greater than or equal to low indicated selected habitat) for each phenological season and life stage, and produced composite maps by selected phenological and reproductive stage to estimate annual habitat. Fourth, we used for each lek within the Bi-State DPS to carry out a spatial analysis that quantified substantial changes in the distribution of occupied habitat across long- (24-year) and short- (11-year) term periods. Owing to differences among available datasets, the long-term analysis primarily reflected spatial shifts among subpopulations comprising the majority of the Bi-State DPS (that is, Bodie Hills and Long Valley) while the short-term analysis also quantified changes among subpopulations along the periphery. Over long and short-term periods, the overall distribution of occupied habitat (as measured by 99 percent utilization distributions intersecting any quantified habitat) was reduced by 20,573 ha and 55,492 ha, respectively. Occupied core areas (as measured by 50 percent utilization distributions intersecting any quantified habitat) over long-term periods were solely located in Bodie Hills and Long Valley. Although nearly all subpopulations experienced contractions in occupied overall and core distribution, Bodie Hills experienced spatial expansion that occurred with concomitant spatial contraction at Long Valley over both periods. Subpopulations at the northern (Pine Nuts), central (Sagehen) and southern (White-Mountains) extents of the Bi-State DPS also experienced spatial contraction over the short-term period. These findings, coupled with those of population trends, indicate long-term patterns in redistribution of sage-grouse from Long Valley and peripheral subpopulations to Bodie Hills. That is, sage-grouse subpopulations at the periphery are declining while the largest population at the core is increasing, which could have meaningful impacts on overall metapopulation persistence. We provide evidence for loss of occupied habitat (reduced distribution) given local extirpation of subpopulations. Fifth, we calculated percentages of selected phenological, life stage, and annual habitat that each subpopulation contributed to the Bi-State DPS. We then intersected these maps with a composite estimate of occupied habitat from the fourth objective and calculated percentages of selected habitat likely occupied by sage-grouse that each subpopulation contributed to the Bi-State DPS. These values provide evidence for loss of occupied habitat and subsequent reductions in spatial distribution given reductions in abundance and, in some cases, extirpation of leks within subpopulations. Lastly, we carried out an initial in-depth analysis of selection for irrigated pastures and wet meadows during the brood-rearing stage for the Long Valley subpopulation. We chose this subpopulation because it represents a population core, representing 26.5 percent of total sage-grouse within the Bi-State DPS, and has exhibited long-term declines in abundance and distribution. This subpopulation is highly sensitive to precipitation and other factors that influence water availability. Models predicted higher use of the interior portions of irrigated pastures and wet meadows during late brood-rearing period, which represented a potentially risky use of habitat that was exacerbated during periods of low moisture (for example, drought, reduced water delivery, or both). Sage-grouse typically used edges of riparian areas and pastures, largely because the interior of these mesic areas consisted of considerably less overhead concealment cover (for example, shrubs) that likely resulted in a higher risk of mortality. We found that a lack of water delivery to pastures in the form of overwinter precipitation or diversion ditches increased the movements of sage-grouse to the interior of pastures. Although further investigation of water delivery impacts on chick survival are warrented, our initial findings regarding resource selection may explain recent declines in population growth at Long Valley.

California, Nevada↗

USGS2018

An integrated population model for greater Sage-Grouse (Centrocercus urophasianus) in the bi-state distinct population segment, California and Nevada, 2003–17

The Bi-State Distinct Population Segment (DPS) of greater sage-grouse ( Centrocercus urophasianus , hereinafter “sage-grouse”) occupies parts of Alpine, Mono, and Inyo Counties in California, and parts of Douglas, Esmeralda, Lyon, Carson City, and Mineral Counties in Nevada and was proposed for listing as threatened under the Endangered Species Act (ESA) by the U.S. Fish and Wildlife Service (USFWS) in October 2013. In April 2015, the USFWS determined that the Bi-State DPS did not warrant listing under the ESA, but monitoring continued for assessment of long-term population stability (U.S. Fish and Wildlife Service, 2015a). Threats to this population include geographic isolation, expansion of single-leaf pinyon ( Pinus monophylla ) and Utah juniper ( Juniperus osteosperma ), anthropogenic activities, changes in historical wildfire cycles and the conversion of native shrubs to invasive annual grasslands, and recent changes in predator communities. As part of a broad long-term monitoring program, we used an integrated population model to estimate finite rate of population change (λ) of each subpopulation within the Bi-State DPS from 2003 to 2017. Since 2012, the Bi-State DPS experienced multiple years of drought conditions associated with periods of population decline across multiple populations. The 14-year average (λ) for the Bi-State DPS is 0.98 (95 percent CRI=0.70–1.31). Three subpopulations (Mount Grant, Fales, Bodie Hills) showed continued evidence of stability and growth as the average λ exceeded 1.0. Moreover, we implemented the first year of an experimental pre-nesting female and brood translocation program to bolster a critically low population of sage-grouse in Parker Meadows, California. Finally, we report summary statistics describing sage-grouse movements and relative abundance of avian predators across all years of the study.

Open-File Report↗

USGS2018

Post-release breeding of translocated sharp-tailed grouse and an absence of artificial insemination effects

Context: Translocation has become a widely used method to restore wildlife populations following extirpation. For some species, such as lekking grouse, which breed at traditional mating grounds, reproduction is linked to culturally established geographic locations. Cultural centres are lost upon extirpation, making restoration into otherwise rehabilitated habitats especially challenging. The process by which species with culturally dependent reproduction sometimes become re-established is poorly understood and merits investigation to improve conservation strategies. Aims: We reintroduced CSTG to vacant habitat in north-central Nevada, USA, from 2013 to 2017, with concordant goals of promoting females to nest and males to lek. We tested the utility of performing artificial insemination (AI) on females before translocation and we conducted paternity analyses to understand male reproduction. Methods: We monitored females for the effects of AI on nest initiation, nest survival and egg fertility. We used post-hatch extra-embryonic membranes and other tissues to evaluate paternity of chicks produced at the restoration site. Key results: Artificial insemination had no effect on female survival or nest initiation, and did not fertilise any eggs within nine sampled clutches ( n = 102 eggs). Most paternity was attributable to male residents that had survived for ≥1 year at the restoration site before the arrival of translocated females. Conclusions: Artificial insemination neither aided nor harmed female reproduction. A small number of translocated, resident adult males sired reproduction following female release. Implications: The presence of resident males at restoration sites may be more likely to result in post-translocation reproduction than is pre-translocation AI. Restoring CSTG to vacant habitat should focus on translocating females into suitable nesting habitat while simultaneously ensuring that reproductively capable males are available within or adjacent to the nesting habitat.

Wildlife Research↗

USGS2016

Survival of translocated sharp-tailed grouse: Temporal threshold and age effects

Context: The Columbian sharp-tailed grouse ( Tympanuchus phasianellus columbianus) is a subspecies of conservation concern in the western United States, currently occupying ≤10% of its historic range. Land and management agencies are employing translocation techniques to restore Columbian sharp-tailed grouse (CSTG) populations. However, establishing self-sustaining populations by translocating grouse often is unsuccessful, owing, in part, to low survivorship of translocated grouse following release. Aims: We measured and modelled patterns of CSTG mortality for 150 days following translocation into historic range, to better understand patterns and causes of success or failure in conservation efforts to re-establish grouse populations. Methods: We conducted two independent multi-year translocations and evaluated individual and temporal factors associated with CSTG survival up to 150 days following their release. Both translocations were reintroduction attempts in Nevada, USA, to establish viable populations of CSTG into their historic range. Key results: We observed a clear temporal threshold in survival probability, with CSTG mortality substantially higher during the first 50 days following release than during the subsequent 100 days. Additionally, translocated yearling grouse exhibited higher overall survival (0.669 ± 0.062) than did adults (0.420 ± 0.052) across the 150-day period and higher survival than adults both before and after the 50-day temporal threshold. Conclusions: Translocated CSTG are especially vulnerable to mortality for 50 days following release, whereas translocated yearling grouse are more resistant to mortality than are adult grouse. On the basis of the likelihood of survival, yearling CSTG are better candidates for population restoration through translocation than are adult grouse. Implications: Management actions that ameliorate mortality factors for 50 days following translocation and translocations that employ yearling grouse will increase the likelihood of population establishment.

Idaho, Nevada↗