Geology topics

Research about Idaho, Montana

Source-linked reports with geographic coverage including Idaho, Montana.

At least 19 recordsLinked to original sources

USGS2025

Bioaccumulation and trophic transfer of selenium in a large oligotrophic river

In flowing waters with elevated selenium concentrations, fish are often considered to be at risk from selenium toxicity owing to dietary exposure and accumulation in ovary tissues and subsequent deformities in developing larvae. We studied selenium throughout components of the aquatic food webs at geomorphically distinct locations along the oligotrophic Kootenai River (Montana and Idaho, USA), a river with moderately elevated dissolved selenium concentrations (~ 1 µg/L). Components included water, sediment, freshly accrued biofilms, in-situ periphyton, sestonic detritus, aquatic invertebrates, and fish, with spring and fall sampling. Selenium concentrations were similar among the sediment, biofilm, periphyton, and detritus samples with most concentrations ranging between 0.5 to 2.0 (mg/kg dry weight (dw)). Among the aquatic invertebrates, the highest selenium concentrations were observed in Paraleptophlebia sp. mayflies (>15 mg/kg dw) and oligochaetes (>30 mg/kg dw). Selenium in chironomids was higher in the spring than fall, but otherwise, no consistent concentration patterns with season or feeding traits were observed. Fish tissue selenium concentrations were highly variable among species and tissue type. Selenium in fish tissues tended to be highest in livers of rainbow trout and mountain whitefish relative to egg/ovary, muscle, and carcass tissue. With northern pikeminnow, redside shiner, and slimy sculpin, selenium concentrations tended to be highest in ovary tissues. For example, selenium in rainbow trout livers ranged from an average (range) of 37 (4.5 to 151) compared to 8.7 (2.7 to 12.3) in northern pikeminnow livers. Egg/ovary concentrations ranged from a high of 26 (10.7 to 64) in redside shiner in contrast to 12.2 (6.9 to 17) mg/kg dw in slimy sculpin. A drawback of the fish-tissue approach to monitoring and managing selenium risks in freshwaters is the need to kill multiple fish per site and event. Potential alternative monitoring approaches are illustrated using aquatic invertebrates or using the food web monitoring results to derive monitoring targets for selenium in water or invertebrate tissue that could avoid the need to kill fish to assess whether fish protection guidelines are met.

Idaho, Montana↗

USGS2024

Leveraging local wildlife surveys for robust occupancy trend estimation

Natural resource agencies are frequently tasked with monitoring populations of at-risk species to ensure management activities do not negatively affect the viability of wildlife populations. Typically, these monitoring efforts evaluate trends in a population’s abundance, occupancy, or geographic distribution. Often, surveys provide local information, but results are generally not incorporated into broad-scale monitoring efforts that focus on range-wide population changes due to their variable nature in both spatial extent and effort. We investigated whether aggregating these local (hereafter “variable”) surveys can generate enough statistical power to estimate broad-scale population trends using simulations of declining populations of fishers ( Pekania pennati ) over a 10-year time horizon. Our simulations included three population sizes which we refer to as abundant, common, and rare ( N 0 = 700, 350, and 100 individuals, respectively) with each declining at a rapid and moderate pace ( λ = 0.933, and 0.977, respectively). For each population, we simulated variable surveys using an occupancy framework to subsample the population with parameters that mimic combining multiple independent monitoring efforts which vary annually in location, and effort. Regardless of spatial consistency of annual sampling, there was minimal variation in statistical power under both high and low detection probability simulations. However, when sampling effort varied each year, statistical power was lower for most populations and sampling scenarios when compared to consistent sampling effort unless some baseline level of sampling effort was reliably achieved in all years. In many cases, adding low-level consistent baseline sampling to variable surveys resulted in statistical power close to that of consistent sampling efforts. Our results suggest statistical power is driven by annual consistency in the proportion of landscape sampled rather than spatial consistency in sampling locations. This result indicates that current variable surveys could be leveraged and combined to detect population declines for at-risk species at broad-scales if a baseline proportion of landscape is robustly sampled. The level of baseline sampling is highly dependent on population size and magnitudes of population change. In simulations with a common or abundant population experiencing a rapid decline, a baseline survey effort of at least 5% of the landscape in combination with variable surveys resulted in statistical power consistently above the standard threshold of 0.80 for occupancy monitoring. Leveraging existing local efforts to achieve high detection probability and baseline sampling would reduce financial and logistical burdens of broad-scale wildlife monitoring efforts.

Idaho, Montana↗

USGS2024

Predicting future grizzly bear habitat use in the Bitterroot Ecosystem under recolonization and reintroduction scenarios

Many conservation actions must be implemented with limited data. This is especially true when planning recovery efforts for extirpated populations, such as grizzly bears ( Ursus arctos ) within the Bitterroot Ecosystem (BE), where strategies for reestablishing a resident population are being evaluated. Here, we applied individual-based movement models developed for a nearby grizzly bear population to predict habitat use in and near the BE, under scenarios of natural recolonization, reintroduction, and a combination. All simulations predicted that habitat use by grizzly bears would be higher in the northern half of the study area. Under the natural recolonization scenario, use was concentrated in Montana, but became more uniform across the northern BE in Idaho over time. Use was more concentrated in east-central Idaho under the reintroduction scenario. Assuming that natural recolonization continues even if bears are reintroduced, use remained widespread across the northern half of the BE and surrounding areas. Predicted habitat maps for the natural recolonization scenario aligned well with outlier and GPS collar data available for grizzly bears in the study area, with Spearman rank correlations of ≥0.93 and mean class values of ≥9.1 (where class 10 was the highest relative predicted use; each class 1–10 represented 10% of the landscape). In total, 52.4% of outlier locations and 79% of GPS collar locations were in class 10 in our predicted habitat maps for natural recolonization. Simulated grizzly bears selected habitats over a much larger landscape than the BE itself under all scenarios, including multiple-use and private lands, similar to existing populations that have expanded beyond recovery zones. This highlights the importance of recognizing and planning for the role of private lands in recovery efforts, including understanding resources needed to prevent and respond to human-grizzly bear conflict and maintain public acceptance of grizzly bears over a large landscape.

Idaho, Montana↗

USGS2024

Evaluation of techniques for estimating the age and growth of known‐age White Sturgeon

Objective Successful conservation and management of fishes require an understanding of their age and growth. However, methods for estimating the age and growth of long-lived fish species are difficult to validate. The Kootenai River basin has a decades-long mark–recapture program for endangered White Sturgeon Acipenser transmontanus . The mark–recapture history information for White Sturgeon allowed for the evaluation of fin rays for age and growth analysis. Methods Age was estimated from pectoral fin rays of known‐age White Sturgeon ( n = 162) to evaluate ageing accuracy and precision. Lengths were back‐calculated using four models and measurements obtained from two fin ray transects (i.e., lateral and posterior). Result Between-reader agreement for White Sturgeon ages was 58.7%. Consensus age agreement with known ages was poor (30.7%) and decreased with age. Among the four back-calculation models, the Fraser–Lee model provided the lowest root mean square error and percent error. Estimates of mean back-calculated lengths at age derived from the Fraser–Lee model were similar between the two measurement transects. Back-calculated lengths at age were similar to known lengths at age. Conclusion Ageing of White Sturgeon using fin rays was unreliable, and accuracy decreased with fish age. Back-calculated lengths at age were accurate using measurements from fin rays of known-age fish. Length estimates from the two measurement transects were similar when using the Fraser–Lee method, suggesting that they may be used interchangeably.

Idaho, Montana↗

USGS2024

A case study and comparison of mid-winter warming and solar driven wet slab avalanche cycles

Wet slab avalanches are poorly understood and often difficult to forecast. Yet, wet slab avalanches can be destructive and may become more common in a changing climate. As the onset of wet avalanches moves earlier in the winter season due to climate change, understanding snowpack and meteorological characteristics of wet slab avalanches will become increasingly important. In this study, we examined two recent late-January wet slab cycles triggered by warming and solar input in the Rocky Mountains of Idaho and Montana, United States. We posed two questions to help us understand these potentially increasingly frequent, mid-winter wet slab cycles: i) what are the weather and snowpack patterns of two mid-winter wet slab cycles and ii) how did these non-rain-on-snow, mid-winter warming events compare to the historical climate normal? In both locations, a short-lived ridge of high pressure strengthened over the region from late January to early February 2024. Temperatures rapidly increased to 6° C at middle and upper-elevation locations and remained above freezing for 48 to 72 hours. Wet slab avalanches (Montana: n=68, Idaho: n=11) released on a layer of facets resting on a crust formed in late December and slab depths averaged 40 to 150 cm. Avalanches primarily occurred on southeast, south, and southwest aspects at middle and upper elevations. Additionally, positive January monthly temperature trends exist in both locations from 1990 to 2020, and these two cycles from 2024 highlight impacts of midwinter warming events with unstable snowpack conditions. These cycles also highlight how a relatively uncommon mid-winter warming event with low radiative input can produce very large destructive wet slab avalanches. Understanding mid-winter warming events and associated wet slab avalanche cycles will help us prepare and forecast for potentially more common scenarios like this in the future.

Idaho, Montana↗

USGS2023

Tungsten resources of the northern Rocky Mountains, Montana and Idaho— A synthesis and quantitative assessment of skarn-hosted resources

Mineral resource assessments performed by the U.S. Geological Survey provide a synthesis of available information about the location of known and suspected mineral deposits. This study focuses on skarn-hosted tungsten resources in the northern Rocky Mountain region of east-central Idaho and western Montana which have seen moderate tungsten trioxide production in the past from a variety of mineralization styles including skarn, vein and replacement, and wolframite-quartz veins. The area’s geology is dominated by large Cretaceous and Tertiary plutons that are emplaced into a belt of Mesoproterozoic to Permian sedimentary rock and affected by tectonism related to the Sevier and later Laramide orogenies. Known tungsten skarn mineral sites are associated with contacts between Cretaceous plutons and calcareous and argillaceous sedimentary or metasedimentary rocks, including two skarn deposits in Montana (Calvert and Browns Lake) that are consistent with an updated grade and tonnage model. This study (1) delineates permissive tracts where undiscovered tungsten skarn deposits may occur within 1 kilometer of the surface; (2) presents a tungsten mineral site dataset from a variety of public sources; (3) evaluates currently available geochemical, geophysical, and radiometric age data in support of tract delineation; (4) provides probabilistic estimates of the amount of tungsten and tungsten-mineralized rock that could be contained in undiscovered deposits within one major tract; (5) estimates the value of total undiscovered deposits using economic filter analysis; and (6) provides a synthesis of metallogenic controls on regional tungsten skarn and granitoid-related mineral deposits. Two permissive tracts were delineated: the Great Falls tectonic zone (GFTZ)-Cretaceous tract, for which a quantitative assessment was performed, and the Bitterroot tract, which was assessed in a qualitative manner. The quantitative three-part assessment, conducted in August 2019, indicates that undiscovered tungsten resources might exist in skarn-type deposits within the study area. Using a negative binomial function, a mean of 4 undiscovered deposits was calculated from panel estimates. Simulation results that combine an updated grade and tonnage model with estimates of undiscovered deposits include the amounts of ore and contained tungsten trioxide at different levels of uncertainty. A mean of 250,000 metric tons and median of 200,000 metric tons contained tungsten trioxide was calculated for the undiscovered deposits within the GFTZ-Cretaceous tract. The value of undiscovered deposits was estimated using a new economic filter that considers factors such as mine type, deposit depth, deposit geometry, metallurgical recovery rate, cutoff grade, and tract area. A review of the regional Archean to Paleogene geology suggests that ore metal (copper, molybdenum, and tungsten) variations in intrusion-related deposits of Montana and Idaho may be controlled by a number of factors including the age and composition of underlying basement terranes, depth of emplacement, pluton chemistry and degree of fractionation, redox conditions, and aqueous fluid-melt partition coefficients.

Idaho, Montana↗

USGS2023

Cryptic declines of small, cold-water specialists highlight potential vulnerabilities of headwater streams as climate refugia

Increasing temperatures and climate-driven disturbances like wildfire are a growing threat to many species, including cold-water specialists. Montane areas and cold streams are often considered climate refugia that buffer communities against change. However, climate refugia are often species-specific, and despite growing awareness that life histories and habitat requirements shape responses to change, small or non-game species are often under-represented in monitoring and planning programs. A recent study in Montana, USA, revealed much larger warming-related declines in occupancy for small, non-game slimy sculpin ( Cottus cognatus ) between 1993 and 1995 and 2011–2013 than for two socially valued salmonid fishes that shape regional conservation efforts. To broaden insight into climate change vulnerabilities of headwater stream communities, we analyzed data for Rocky Mountain tailed frogs ( Ascaphus montanus ) that were collected during those same electrofishing surveys for fishes from 241 stream reaches. Tailed frogs occupy small, cold streams and have several life-history traits that make them sensitive to environmental change. We used a Bayesian framework to estimate occupancy, colonization, and extinction dynamics relative to forest canopy, estimated stream temperature, and wildfire effects. Tailed frog occupancy decreased by 19 % from 1993 to 1995 to 2011–2013. Changes in occupancy were linked with increased extinction and reduced colonization where there were fire-driven reductions in canopy cover, and reduced colonization of stream reaches that warmed on average 0.8 °C during the study. Our results highlight extensive extirpations for oft-overlooked species and emphasize the importance of including species with diverse habitat requirements and life histories in conservation planning.

Idaho, Montana↗

USGS2022

Individual characteristics and abiotic factors influence out-migration dynamics of juvenile bull trout

Fragmentation of rivers through anthropogenic modifications poses an imminent threat to the persistence of migratory fish, necessitating direct actions such as trap-and-haul programs to restore and conserve the migratory life-history component in populations of partially migratory species such as bull trout Salvelinus confluentus. We used a PIT-tag system to assess how biological and abiotic factors influence the out-migration dynamics of juvenile bull trout in Graves Creek, Montana, USA. The largest fish within a cohort were more likely to out-migrate at age 1 when compared to smaller fish within the cohort, and this was particularly evident in a high-density year-class (2018), where large bull trout out-migrated an average of 115 days earlier than bull trout in the medium size category, and 181 days earlier than bull trout in the small size category. Relative changes in abiotic factors, including discharge, water temperature, and photoperiod, appeared to act as cues to out-migration, with the direction of change varying by season. These results highlight the complex interplay between individual characteristics, population dynamics, and environmental conditions, which influence out-migration dynamics and can be used to inform management actions to conserve the migratory component in bull trout populations.

Idaho, Montana↗

USGS2022

Temporal variation in capture efficiency underrepresents spring out-migrating Bull Trout in a trap-and-haul program

Trap-and-haul programs can maintain connection among habitats for migratory salmonids in fragmented systems. To conserve diversity within and among life history strategies, downstream trap and transport of juvenile salmonids could ideally mimic the natural, underlying out-migration dynamics of the population. A two-way trap-and-haul program is implemented in the lower Clark Fork River, Montana, to conserve adfluvial Bull Trout Salvelinus confluentus. We used PIT technology to assess whether downstream trapping efforts are effectively capturing variation in the out-migration dynamics of juvenile Bull Trout in Graves Creek, a key spawning and rearing tributary in the system. We tagged 821 juvenile Bull Trout in Graves Creek and used these tagged Bull Trout in conjunction with stationary PIT antennas to monitor out-migration and evaluate efficiency of the downstream trapping program. Capture efficiency in Graves Creek varied substantially from autumn to spring, with 89–96% of autumn out-migrating Bull Trout captured and 5–10% of spring out-migrating Bull Trout captured. Overall, we found that Bull Trout transported during the autumn out-migration periods generally reflect the natural out-migration dynamics of the population; however, Bull Trout that out-migrate in the spring are currently underrepresented in the downstream transport program. By understanding the underlying out-migration dynamics of the Bull Trout population in Graves Creek, management of the downstream trapping efforts can focus on minimizing potential selection for or against out-migrants based on timing and age at out-migration. Minimizing selection will conserve variation within the adfluvial life history strategy and therefore maximize resilience of the adfluvial Bull Trout populations.

Idaho, Montana↗

USGS2022

Nutrient restoration of a large, impounded, ultra-oligotrophic western river to recover declining native fishes

Declines in many fish populations in large, western rivers have been primarily attributed to the anthropogenic reduction of nutrient inputs and subsequent impacts to the food web. The largest known river fertilization program was implemented starting in 2005 on the Kootenai River in northern Idaho to restore resident fisheries. Annual electrofishing surveys were conducted at multiple sites in Idaho and Montana before and during nutrient addition to evaluate assemblage and population-level responses. Although few responses in fish assemblage structure were observed, the addition of liquid ammonium polyphosphate fertilizer (3 μg/L) to the Kootenai River increased fish abundance and biomass over the 20-km stretch of river downstream of the treatment site. Increases were most notable in Largescale Suckers Catostomus macrocheilus, Mountain Whitefish Prosopium williamsoni , and Rainbow Trout Oncorhynchus mykiss populations, although increases in catch and biomass were detected for nearly all fish species . The Kootenai River is approximately 30 times larger in discharge than other rivers that have been experimentally fertilized and provides compelling evidence that the mitigation of nutrient declines in rivers of similar size can result in positive influences on the fish populations where primary and secondary production are limiting growth, survival, and recruitment. However, results from our study also highlight the importance of completing evaluations across varying levels of biological organization (e.g., assemblage and population) and over biologically relevant timeframes.

Idaho, Montana↗

USGS2022

Hydroclimatic conditions, wildfire, and species assemblages influence co-occurrence of bull trout and tailed frogs in northern Rocky Mountain streams

Although bull trout ( Salvelinus confluentus ) and tailed frogs ( Ascaphus montanus ) have co-existed in forested Pacific Northwest streams for millennia, these iconic cold-water specialists are experiencing rapid environmental change caused by a warming climate and enhanced wildfire activity. Our goal was to inform future conservation by examining the habitat associations of each species and conditions that facilitate co-occupancy. We repurposed data from previous studies in the northern Rocky Mountains to assess the efficacy of bull trout electrofishing surveys for determining the occurrence of tailed frogs and the predictive capacity of habitat covariates derived from in-stream measurements and geospatial sources to model distributions of both species. Electrofishing reliably detected frog presence (89.2% rate). Both species were strongly associated with stream temperature and flow regime characteristics, and less responsive to riparian canopy cover, slope, and other salmonids. Tailed frogs were also sensitive to wildfire, with occupancy probability peaking around 80 years after a fire. Co-occupancy was most probable in locations with low-to-moderate frequencies of high winter flow events, few other salmonids, a low base-flow index, and intermediate years since fire. The distributions of these species appear to be sensitive to environmental conditions that are changing this century in forests of the northern Rocky Mountains. The amplification of climate-driven effects after wildfire may prove to be particularly problematic in the future. Habitat differences between these two species, considered to be headwater specialists, suggest that conservation measures designed for one may not fully protect the other. Additional studies involving future climate and wildfire scenarios are needed to assess broader conservation strategies and the potential to identify refuge streams where both species are likely to persist, or complementary streams where each could exist separately into the future.

Idaho, Montana↗

USGS2022

Exposure of cultural resources to 21st-century climate change: Towards a risk management plan

Anthropogenic climate change during the 21st century presents a significant challenge to the protection of cultural resources (CRs) on federal lands that encompass ∼ 28% of the U.S. In particular, CRs on this land base may be adversely affected by a wide range of climate-change hazards, including damage by sea-level rise, enhanced deterioration by increasing temperature and precipitation, and destruction by more-frequent and severe wildfire. Most current measures to manage the impacts of hazards on CRs use vulnerability assessments, but because these require that all CRs be treated as having an equal chance of being affected by climate-change hazards (i.e., equal exposure) across large landscapes, the cost and resources required for such analyses are overwhelming to land management agencies. Projections of changes in many hazards, however, show that the probability of hazard occurrence will be unevenly distributed on the landscape. Incorporating this information into a risk assessment thus allows CR managers to prioritize their efforts on assessing impacts to CRs in those areas where the probability of the hazard is greatest, thus increasing efficiency. We provide several heuristic examples of implementing the first part of a CR risk assessment by using 21st-century projections of several hazards most likely to adversely affect CRs on nine National Forests (NFs) managed by the U.S. Forest Service in northern Idaho and Montana. Overlaying the projected distribution of hazards on these NFs with the distribution of CRs identifies CR exposure that, with information on their vulnerability, is required to determine risk. Additional policy and field studies will be needed to determine how to prioritize those CRs that are most at risk according to their significance as well as identify how impacts can be reduced and managed through adaptation planning and implementation. Adaptation will follow the iterative risk management process particularly by improving projection resolution. Finer scale, process-based modeling informed by the highest priority CRs would also provide a means to assess various adaptation options that might change the estimated risk and increase the odds of CRs being as little affected as possible.

Idaho, Montana↗

USGS2021

Factors influencing distributional shifts and abundance at the range core of a climate-sensitive mammal

Species are frequently responding to contemporary climate change by shifting to higher elevations and poleward to track suitable climate space. However, depending on local conditions and species’ sensitivity, the nature of these shifts can be highly variable and difficult to predict. Here, we examine how the American pika ( Ochotona princeps ), a philopatric, montane lagomorph, responds to climatic gradients at three spatial scales. Using mixed-effects modeling in an information-theoretic approach, we evaluated a priori model suites regarding predictors of site occupancy, relative abundance, and elevational-range retraction across 760 talus patches, nested within 64 watersheds across the Northern Rocky Mountains of North America, during 2017–2020. The top environmental predictors differed across these response metrics. Warmer temperatures in summer and winter were associated with lower occupancy, lower relative abundances, and greater elevational retraction across watersheds. Occupancy was also strongly influenced by habitat patch size, but only when combined with climate metrics such as actual evapotranspiration. Using a second analytical approach, acute heat stress and summer precipitation best explained retraction residuals (i.e., the relative extent of retraction given the original elevational range of occupancy). Despite the study domain occurring near the species’ geographic-range center, where populations might have higher abundances and be at lower risk of climate-related stress, 33.9% of patches showed evidence of recent extirpations. Pika-extirpated sites averaged 1.44℃ warmer in summer than did occupied sites. Additionally, the minimum elevation of pika occupancy has retracted upslope in 69% of watersheds (mean: 281 m). Our results emphasize the nuance associated with evaluating species’ range dynamics in response to climate gradients, variability, and temperature exceedances, especially in regions where species occupy gradients of conditions that may constitute multiple range edges. Furthermore, this study highlights the importance of evaluating diverse drivers across response metrics to improve the predictive accuracy of widely used, correlative models.

Idaho, Montana↗

USGS2021

Improving inferences about private land conservation by accounting for incomplete reporting

Private lands provide key habitat for imperiled species and are core components of function protected area networks; yet, their incorporation into national and regional conservation planning has been challenging. Identifying locations where private landowners are likely to participate in conservation initiatives can help avoid conflict and clarify trade-offs between ecological benefits and sociopolitical costs. Empirical, spatially explicit assessment of the factors associated with conservation on private land is an emerging tool for identifying future conservation opportunities. However, most data on private land conservation are voluntarily reported and incomplete, which complicates these assessments. We used a novel application of occupancy models to analyze the occurrence of conservation easements on private land. We compared multiple formulations of occupancy models with a logistic regression model to predict the locations of conservation easements based on a spatially explicit social-ecological systems framework. We combined a simulation experiment with a case study of easement data in Idaho and Montana (United States) to illustrate the utility of the occupancy framework for modeling conservation on private land. Occupancy models that explicitly accounted for variation in reporting produced estimates of predictors that were substantially less biased than estimates produced by logistic regression under all simulated conditions. Occupancy models produced estimates for the 6 predictors we evaluated in our case study that were larger in magnitude, but less certain than those produced by logistic regression. These results suggest that occupancy models result in qualitatively different inferences regarding the effects of predictors on conservation easement occurrence than logistic regression and highlight the importance of integrating variable and incomplete reporting of participation in empirical analysis of conservation initiatives. Failure to do so can lead to emphasizing the wrong social, institutional, and environmental factors that enable conservation and underestimating conservation opportunities in landscapes where social norms or institutional constraints inhibit reporting.

Idaho, Montana↗

USGS2020

Reptiles under the conservation umbrella of the greater sage‐grouse

In conservation paradigms, management actions for umbrella species also benefit co‐occurring species because of overlapping ranges and similar habitat associations. The greater sage‐grouse ( Centrocercus urophasianus ) is an umbrella species because it occurs across vast sagebrush ecosystems of western North America and is the recipient of extensive habitat conservation and restoration efforts that might benefit sympatric species. Biologists' understanding of how non‐target species might benefit from sage‐grouse conservation is, however, limited. Reptiles, in particular, are of interest in this regard because of their relatively high diversity in shrublands and grasslands where sage‐grouse are found. Using spatial overlap of species distributions, land cover similarity statistics, and a literature review, we quantified which reptile species may benefit from the protection of intact sage‐grouse habitat and which may be affected by recent (since about 1990) habitat restoration actions targeting sage‐grouse. Of 190 reptile species in the United States and Canadian provinces where greater sage‐grouse occur, 70 (37%) occur within the range of the bird. Of these 70 species, about a third (11 snake and 11 lizard species) have >10% of their distribution area within the sage‐grouse range. Land cover similarity indices revealed that 14 of the 22 species (8 snake and 6 lizard species) had relatively similar land cover associations to those of sage‐grouse, suggesting greater potential to be protected under the sage‐grouse conservation umbrella and greater potential to be affected, either positively or negatively, by habitat management actions intended for sage‐grouse. Conversely, the remaining 8 species are less likely to be protected because of less overlap with sage‐grouse habitat and thus uncertain effects of sage‐grouse habitat management actions. Our analyses of treatment databases indicated that from 1990 to 2014 there were at least 6,400 treatments implemented on public land that covered approximately 4 million ha within the range of the sage‐grouse and, of that, >1.5 million ha were intended to at least partially benefit sage‐grouse. Whereas our results suggest that conservation of intact sagebrush vegetation communities could benefit ≥14 reptiles, a greater number than previously estimated, additional research on each species' response to habitat restoration actions is needed to assess broader claims of multi‐taxa benefits when it comes to manipulative sage‐grouse habitat management. Published 2020. This article is a U.S. Government work and is in the public domain in the USA.

Idaho, Montana↗

USGS2018

Geologic map of the central Beaverhead Mountains, Lemhi County, Idaho, and Beaverhead County, Montana

This geologic map of the central Beaverhead Mountains portrays a complex geologic history of depositional basin development interspersed with deformational events. Generalized geology for young basins, compiled from sources on both sides of the range, is combined with newly mapped bedrock geology to better integrate geologic development of the map area. Successive extensional basins were obliquely oriented across deformed strata of each preceding basin and of the Paleoproterozoic basement. Strata deposited in these basins include (1) thick fine-grained arkosic strata of the Mesoproterozoic Lemhi basin deposited on Paleoproterozoic basement with shoreline exposed on the east side of the map, (2) siliciclastic and carbonate strata of the Late Neoproterozoic-early Paleozoic miogeocline that were deposited in deeper environments to the west and interfingered with cratonal basin deposits to the east, and (3) generally coarse deposits in several nested, fault-bounded Eocene to Holocene basins. Syndepositional structural disruption including tilting and angular unconformities is present within strata and between stratigraphic packages formed during the different basin-filling events. Cretaceous, east-northeast-directed thrust faults inverted Mesoproterozoic and Neoproterozoic-Paleozoic basins and stacked strata from diverse stratigraphic packages and different depositional settings. The thrust plates rotated as they impinged on the Paleoproterozoic arch on the east side of the map, resulting in complex fault geometries that present as thrust faults to oblique reverse and tear (or ramp) fault along different fault segments. Cenozoic extension caused successive normal-fault basins of several orientations. Eocene volcanic rocks are preserved in fault-bounded depositional basins formed during the onset of Cenozoic extension. Eocene basins were obliquely overprinted by Oligocene-Miocene normal-fault basins. Holocene basins developed during steep normal faulting that formed the present Basin and Range topography. This geologic map of the central Beaverhead Mountains is mapped at 1:24,000 scale and printable at 1:50,000 scale. These data were collected between 1997 and 2017 and synthesized to provide significant new stratigraphic and structural data and interpretations.

Idaho, Montana↗

USGS2018

Long-term population dynamics and conservation risk of migratory bull trout in the upper Columbia River basin

We used redd count data from 88 bull trout (Salvelinus confluentus) populations in the upper Columbia River basin to quantify local and regional patterns in population dynamics, including adult abundance, long-term trend, and population synchrony. We further used this information to assess conservation risk of metapopulations using eight population dynamic metrics associated with persistence. Local population abundances were generally low (<20 redds annually) and the majority of trends were either stable (85%) or declining (13%). Evidence of synchrony among populations was apparent but not related to fluvial distance between streams. Variability in annual abundances was 1.4–2.5 times lower in metapopulations than local populations, indicating moderate portfolio effects across the regional stock complex. Importantly, most metrics of conservation risk were uncorrelated with one another, emphasizing that multiple statistics describing population dynamics at various scales are needed for monitoring and assessing recovery. We provide a composite description of conservation risk based on local and regional population dynamics that can help inform conservation management decisions for bull trout and other freshwater fishes.

Idaho, Montana↗

USGS2016

Movement and survival of an amphibian in relation to sediment and culvert design

Habitat disturbance from stream culverts can affect aquatic organisms by increasing sedimentation or forming barriers to movement. Land managers are replacing many culverts to reduce these negative effects, primarily for stream fishes. However, these management actions are likely to have broad implications for many organisms, including amphibians in small streams. To assess the effects of culverts on movement and survival of the Idaho giant salamander ( Dicamptodon aterrimus ), we used capture-mark-recapture surveys and measured sediment in streams with 2 culvert types (i.e., unimproved culverts, improved culverts) and in streams without culverts (i.e., reference streams). We predicted culverts would increase stream sediment levels, limit movement, and reduce survival of Idaho giant salamanders. We also determined the effect of sediment levels on survival of salamanders because although sediment is often associated with distribution and abundance of stream amphibians, links with vital rates remain unclear. To estimate survival, we used a spatial Cormack–Jolly–Seber (CJS) model that explicitly incorporated information on movement, eliminating bias in apparent survival estimated from traditional (i.e., non-spatial) CJS models caused by permanent emigration beyond the study area. To demonstrate the importance of using spatial data in studies of wildlife populations, we compared estimates from the spatial CJS to estimates of apparent survival from a traditional CJS model. Although high levels of sediment reduced survival of salamanders, culvert type was unrelated to sediment levels or true survival of salamanders. Across all streams, we documented only 15 movement events between study reaches. All movement events were downstream, and they occurred disproportionately in 1 stream, which precluded measuring the effect of culvert design on movement. Although movement was low overall, the variance among streams was high enough to bias estimates of apparent survival compared to true survival. Our results suggest that where sedimentation occurs from roads and culverts, survival of the Idaho giant salamander could be reduced. Though culverts clearly do not completely block downstream movements of Idaho giant salamanders, the degree to which culvert improvements affect movements under roads in comparison to unimproved culverts remains unclear, especially for rare, but potentially important, upstream movements.

Idaho, Montana↗