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Brome McCreary

Publications and source records attributed to Brome McCreary.

18 recordsLinked to original sources
USGS2025

Pan-amphibia distribution of the fungal parasite Batrachochytrium dendrobatidis varies with species and temperature

Batrachochytrium dendrobatidis (Bd) is a globally distributed fungal pathogen of amphibians that has contributed to one of the largest disease-related biodiversity losses in wildlife. Bd is regularly viewed through the lens of a global wildlife epizootic because the spread of highly virulent genetic lineages has resulted in well-documented declines and extinctions of multiple amphibian species. However, the current state of Bd occurrence, host range, host impacts, and ecological drivers remains poorly understood outside of the most negatively affected amphibian species and regions. Our objective was to describe the macroecology of Bd occurrence and infection intensity on caudates (salamanders) across the United States and to compare these patterns with better-studied anurans (frogs and toads). We collected swabs from 11,183 amphibians at 609 sites from 54 species across the United States from 2015 to 2017. We analyzed the prevalence and intensity of Bd infection jointly using a Bayesian hurdle model with covariates of site-level temperature and precipitation, as well as individual characteristics and species identification. Bd was distributed widely across sites and species sampled across the spatial extent of the conterminous United States. We found that Bd prevalence and intensity were most strongly influenced by temperature in the month preceding sampling and by differences among taxon groups. We estimated that temperature had a strong and nonlinear influence on both Bd prevalence and intensity with peak infection at intermediate temperatures and lower infection at low and high temperatures. We found Caudate hosts tended to have higher prevalence than Anuran hosts and Anuran hosts tended to have higher intensity at optimal temperatures for Bd infection. Our findings suggest that Bd has an amphibian-wide host range, temperature gradients exert a strong influence on Bd, and enzootic transmission likely encompasses a much larger spatial and species distribution than previously recognized across North America.

conterminous United States↗
USGS2023

Population dynamics of the threatened Oregon spotted frog before and after drought mitigation

Amphibians are among the most sensitive taxa to climate change, and species inhabiting arid and semiarid landscapes at the extremes of their range are especially vulnerable to drought. The Jack Creek, Oregon, USA, population of Oregon spotted frogs ( Rana pretiosa ) faces unique challenges because it occupies the highest elevation site in the species' extant range and one that has been transformed by loss of American beavers ( Castor canadensis ), which historically maintained open water. We evaluated the effects of drought mitigation (addition of excavated ponds) on relationships between local and regional water availability, inactive legacy beaver dams, and Oregon spotted frog population dynamics in the Jack Creek system. We conducted egg mass surveys and capture-mark-recapture sampling at a treatment reach with excavated ponds and 3 reference reaches over 13 years; surveys spanned a period before and after pond excavation at the treatment and 1 primary comparison reference reach. We analyzed data using a combination of robust design capture-mark-recapture estimators and generalized linear mixed models to characterize population dynamics. Adult Oregon spotted frog survival was approximately 19.5% higher at the treatment reach than the primary reference reach during the study period. Annual survival was most strongly associated with late summer vegetation greenness, a proxy for water availability, and males had higher survival than females. Among the 4 study reaches, the treatment reach consistently had higher late summer vegetation greenness, and the hydrology functioned more independently of regional precipitation patterns relative to the reference reaches; however, these dynamics were not linked to pond excavation. Breeding was concentrated in 2 legacy beaver ponds that were deepened by excavation during the study compared to an unexcavated beaver pond, 2 excavated ponds without legacy beaver dams, and 9 reference ponds. These results point to the benefit of enhancing existing beaver structures and indicate that management actions aimed at maintaining surface water for breeding in spring and saturated soils and ponded water for adults in late summer would benefit this unique population of Oregon spotted frogs in the face of drought.

Oregon↗
USGS2022

Late season movement and habitat use by Oregon spotted frog (Rana pretiosa) in a large reservoir in Oregon, USA

Dam-created reservoirs are common landscape features that can provide habitat for amphibians, but their water level fluctuations and nonnative predators can differ markedly from more natural habitats. We compared fall movement and habitat use by the Oregon Spotted Frog ( Rana pretiosa ) in the reservoir pool with nearby river and pond habitats at Crane Prairie Reservoir in central Oregon, USA. Movement rate of frogs in the river and ponds declined as water temperature cooled. Reservoir frogs moved further than those in the river or ponds, and their movement rate increased as water temperature cooled. Most frog locations across all site types were in aquatic herbaceous vegetation. We did not find shifts in habitat between early and late fall. Increased movement and the lack of habitat shift in our reservoir frogs deeper into fall contrast with R. pretiosa in non-reservoir sites in this study and others. Consistent use of vegetation by reservoir frogs throughout the fall could indicate cover use in presence of fish predators. Our study provides additional detail on the range of habitats used by R. pretiosa in fall and suggests areas for further work to improve survival in constructed sites with abundant fish predators.

Oregon↗
USGS2021

Demography of the Oregon spotted frog along a hydrologically modified river

Altered flow regimes can contribute to dissociation between life history strategies and environmental conditions, leading to reduced persistence reported for many wildlife populations inhabiting regulated rivers. The Oregon spotted frog ( Rana pretiosa ) is a threatened species occurring in floodplains, ponds, and wetlands in the Pacific Northwest with a core range in Oregon, USA. All life stages of R. pretiosa are reliant on aquatic habitats, and inundation patterns across the phenological timeline can have implications for population success. We conducted capture–mark–recapture (CMR) sampling of adult and subadult R. pretiosa at three sites along the Deschutes River downstream from two dams that regulate flows. We related the seasonal extent of inundated habitat at each site to monthly survival probabilities using a robust design CMR model. We also developed matrix projection models to simulate population dynamics into the future under current river flows. Monthly survival was strongly associated with the extent and variability of inundated habitat, suggesting some within-season fluctuations at higher water levels could be beneficial. Seasonal survival was lowest in the winter for all three sites, owing to limited water availability and the greater number of months within this season relative to other seasons. Population growth for the two river-connected sites was most strongly linked to adult survival, whereas population growth at the river-disconnected site was most strongly tied to survival in juvenile stages. This research identifies population effects of seasonally limited water and highlights conservation potential of enhancing survival of particularly influential life stages.

Oregon↗
USGS2021

Monitoring wetland water quality related to livestock grazing in amphibian habitats

Land use alteration such as livestock grazing can affect water quality in habitats of at-risk wildlife species. Data from managed wetlands are needed to understand levels of exposure for aquatic life stages and monitor grazing-related changes afield. We quantified spatial and temporal variation in water quality in wetlands occupied by threatened Oregon spotted frog ( Rana pretiosa ) at Klamath Marsh National Wildlife Refuge in Oregon, United States (US). We used analyses for censored data to evaluate the importance of habitat type and grazing history in predicting concentrations of nutrients, turbidity, fecal indicator bacteria (FIB; total coliforms, Escherichia coli ( E. coli ), and enterococci), and estrogenicity, an indicator of estrogenic activity. Nutrients (orthophosphate and ammonia) and enterococci varied over time and space, while E. coli , total coliforms, turbidity, and estrogenicity were more strongly associated with local livestock grazing metrics. Turbidity was correlated with several grazing-related constituents and may be particularly useful for monitoring water quality in landscapes with livestock use. Concentrations of orthophosphate and estrogenicity were elevated at several sites relative to published health benchmarks, and their potential effects on Rana pretiosa warrant further investigation. Our data provided an initial assessment of potential exposure of amphibians to grazing-related constituents in western US wetlands. Increased monitoring of surface water quality and amphibian population status in combination with controlled laboratory toxicity studies could help inform future research and targeted management strategies for wetlands with both grazing and amphibians of conservation concern.

Oregon↗
USGS2021

An updated assessment of status and trend in the distribution of the Cascades frog (Rana cascadae) in Oregon, USA

Conservation efforts need reliable information concerning the status of a species and their trends to help identify which species are in most need of assistance. We completed a comparative evaluation of the occurrence of breeding for Cascades Frog ( Rana cascadae ), an amphibian that is being considered for federal protection under the U.S. Endangered Species Act. Specifically, in 2018–2019 we resurveyed 67 sites that were surveyed approximately 15 y prior and fit occupancy models to quantify the distribution of R. cascadae breeding in the Cascade Range, Oregon, USA. Furthermore, we conducted a simulation exercise to assess the power of sampling designs to detect declines in R. cascadae breeding at these sites. Our analysis of field data combined with our simulation results suggests that if there was a decline in the proportion of sites used for R. cascadae breeding in Oregon, it was likely a < 20% decline across our study period. Our results confirm that while R. cascadae detection probabilities are high, methods that allow the sampling process to be explicitly modeled are necessary to reliably track the status of the species. This study demonstrates the usefulness of investing in baseline information and data quality standards to increase capacity to make similar comparisons for other species in a timeframe that meet the needs of land managers and policy makers.

Oregon↗
USGS2020

Estimation of metademographic rates and landscape connectivity for a conservation-reliant anuran

Context Amphibian conservation efforts commonly assume populations are tied to waterbodies that collectively function as a metapopulation. This assumption is rarely evaluated, and there is a need to understand the degree of connectivity among patches to appropriately define, manage, and conserve biological populations. Objectives Our objectives were to quantify local persistence, colonization, and recruitment (metademographic rates) in relation to habitat attributes, evaluate the influence of the spatial arrangement of patches on landscape-scale population dynamics, and estimate the scale at which metapopulation dynamics are occurring for Oregon spotted frog ( Rana pretiosa ). Methods We collected R. pretiosa detection/non-detection data and habitat information from 93 sites spread throughout the species’ extant range in Oregon, USA, 2010–2018. We developed a spatial multistate dynamic occupancy model to analyze these data. Results The proportion of sites occupied by R. pretiosa was relatively stable despite regular turnover in site occupancy. Connectivity was greatest when the distance between sites was within 4.49–7.70 km, and the results suggested that populations within 1 km are at the appropriate spatial scale for effective population management. Rana pretiosa metademographic rates were strongly tied to water availability, vegetation characteristics, and beaver dams. Conclusions Our analysis provides critical information to identify the appropriate spatial scale for effective population management, estimates the distance at which populations are connected, and quantifies the effects of hypothesized threats to species at a landscape scale. We believe this model will prove to be useful to inform conservation and management strategies for multiple species.

Oregon↗
USGS2019

Disentangling effects of invasive species and habitat while accounting for observer error in a long-term amphibian study

The invasive American bullfrog ( Lithobates catesbeianus ) and a variety of non‐native sport fish commonly co‐occur in lowland lentic habitats of the western United States. Both invasive taxa are implicated in declines of native amphibians in this region, but few long‐term studies of communities exist. Further, field studies of invasive–native interactions are complicated by confounding habitat modifications and observation errors. We surveyed amphibians and measured habitat characteristics for 12 yr across 38 wetland sites within the Willamette Valley, Oregon, USA. We assessed the influence of invasive species, habitat, and their interactions on the distributions of five native amphibian species using a multispecies dynamic occupancy model that accounted for false‐negative and false‐positive detections. In general, habitat characteristics—such as within‐pond vegetation cover, surrounding forest, and drought severity—were important for local persistence of native species when bullfrogs co‐occurred. We also found evidence of a cumulative negative effect of bullfrogs and non‐native fish (families Centrarchidae and Ictaluridae) on northern red‐legged frog ( Rana aurora ) local persistence that was mediated by the dominance of invasive reed canarygrass ( Phalaris arundinacea ). Non‐native fish and bullfrogs had variable effects on native amphibian species, but neither invasive taxon appears to be causing declines in occupied sites within our study area. Moreover, species relationships with habitat differed when invaders were present, indicating that certain habitats may increase persistence of native amphibians in the invaded landscape.

Oregon↗
USGS2018

Effect of cattle exclosures on Columbia Spotted Frog abundance

Livestock grazing is an important land use in the western USA and can have positive or negative effects on amphibians. Columbia Spotted Frog ( Rana luteiventris ) often use ponds that provide water for cattle. We conducted a long-term manipulative study on US Forest Service land in northeastern Oregon to determine the effects of full and partial exclosures that limited cattle access to ponds used by frogs. We found weak evidence of a short-term increase in abundance that did not differ between full and partial exclosures and that diminished with continuing exclusion of cattle. The benefit of exclosures was small relative to the overall decline in breeding numbers that we documented. This suggests that some protection can provide a short-term boost to populations.

Wetlands Ecology and Management↗
USGS2018

Late-season movement and habitat use by Oregon spotted frogs (Rana pretiosa) in Oregon, USA

Many amphibians use multiple habitats across seasons. Information on seasonal habitat use, movement between seasonal habitat types, and habitats that may be particularly valuable is important to conservation and management. We used radio-telemetry to study late-season movement and habitat use by Oregon Spotted Frog ( Rana pretiosa ) at nine sites from four populations along the Cascade Mountains in Oregon. Movement rates declined with date and were the lowest at the end of tracking in December and January. Frogs across our sites used vegetated shallows in late summer and early fall. In fall, frogs used a range of habitat types, and at several sites moved to distinctive habitats such as springs, interstices in lava rock, and semi-terrestrial beaver channels. Distance between first and last tracking location was <250 m for 84.5% (49/58) of frogs, ranged up to 1145 m, and was greater for frogs in ditch habitats than those not in ditches. Distinctive features like springs or semi-terrestrial retreats can host multiple frogs and may represent particularly valuable wintering habitat for R. pretiosa in some sites in their Oregon range.

Oregon↗
USGS2014

Short-term occupancy and abundance dynamics of the Oregon spotted frog (Rana pretiosa) across its core range

The Oregon spotted frog ( Rana pretiosa ) occupies only a fraction of its original range and is listed as Threatened under the Endangered Species Act. We surveyed 93 sites in a rotating frame design (2010&ndash;13) in the Klamath and Deschutes Basins, Oregon, which encompass most of the species&rsquo; core extant range. Oregon spotted frogs are declining in abundance and probability of site occupancy. We did not find an association between the probability that Oregon spotted frogs disappear from a site (local extinction) and any of the variables hypothesized to affect Oregon spotted frog occupancy. This 4-year study provides baseline data, but the 4-year period was too short to draw firm conclusions. Further study is essential to understand how habitat changes and management practices relate to the status and trends of this species.

Oregon↗
USGS2013

Habitat and co-occurrence of native and invasive crayfish in the Pacific Northwest, USA

Biological invasions can have dramatic effects on freshwater ecosystems and introduced crayfish can be particularly impacting. We document crayfish distribution in three large hydrographic basins (Rogue, Umpqua, Willamette/Columbia) in the Pacific Northwest USA. We used occupancy analyses to investigate habitat relationships and evidence for displacement of native Pacifastacus leniusculus (Dana, 1852) by two invaders. We found invasive Procambarus clarkii (Girard, 1852), in 51 of 283 sites and in all three hydrographic basins. We found invasive Orconectes n. neglectus (Faxon, 1885) at 68% of sites in the Rogue basin and provide first documentation of their broad distribution in the Umpqua basin. We found P. clarkii in both lentic and lotic habitats, and it was positively associated with manmade sites. P. leniusculus was positively associated with lotic habitats and negatively related to manmade sites. In the Rogue and Umpqua basins, O. n. neglectus and P. leniusculus were similar in their habitat associations. We did not find a negative relationship in site occupancy between O. n. neglectus and P. leniusculus. Our data suggest that P. clarkii has potential to locally displace P. leniusculus. There is still time for preventive measures to limit the spread of the invasive crayfish in this region.

Aquatic Invasions↗
USGS2011

Non-native species impacts on pond occupancy by an anuran

Non‐native fish and bullfrogs ( Lithobates catesbeianus ) are frequently cited as contributing to the decline of ranid frogs in the western United States, so we hypothesized that non‐native species, habitat, or a combination of these relate to the probability of local extinction for northern red‐legged frogs ( Rana aurora ) in Oregon, USA. We also hypothesized that the probability of colonization relates to land use, wetland size, or riparian forest. In a 5‐yr study, we found no support for an effect of non‐native species on northern red‐legged frogs. Instead, probability of local extinction decreased with the extent of emergent vegetation and riparian forest. This finding suggests that managers consider the role of habitat when confronting non‐native species problems.

Oregon↗
USGS2011

Invasive crayfish in the Pacific Northwest

Invasive species directly threaten freshwater biodiversity, particularly in regions of high aquatic richness like the Pacific Northwest (PNW). Crayfish are among the most impactful of aquatic invasive species. Invasive crayfish are considered ecosystem engineers due to their ability to alter basic wetland properties, such as reducing vegetation and bank integrity and increasing turbidity. In areas where invasion is advanced, crayfish pose major economic and ecological problems. Crayfish have been widely introduced for aquaculture and can become established in a wide range of habitat conditions. They also may be spread by anglers who use them as bait. Several non-native crayfish are established in the PNW, but the extent of their invasion is not well known. At least two groups are known from scattered sites in the PNW, and both have proven problematic for native species in other parts of the world: Red swamp crayfish ( Procambarus clarkii ) and several members of the genus Orconectes . Both groups are native to areas of the eastern United States. Both are identified globally as invasives of high concern and appear on the Oregon Department of Fish and Wildlife's "10 Most Unwanted" and the U.S. Forest Service's "Primary Species of Concern" lists for stream systems in the PNW. Despite the presence of introduced crayfish in the PNW and their high potential for negative effects, the scope of their invasion and effects on aquatic systems are not well known. The U.S. Geological Survey (USGS), along with local groups and state agencies, is working to clarify crayfish distribution and to outline which basins may not yet be invaded. Other goals are to improve understanding of habitat associations of invasive crayfish and their potential effects on native crayfish.

Pacific Northwest↗
USGS2010

Columbia spotted frog (Rana luteiventris) in southeastern Oregon: A survey of historical localities, 2009

The Columbia spotted frog (Rana luteiventris) occupies a large range in western North America and is comprised of at least three genetic units. Concern exists regarding the status of the Great Basin populations in Oregon, Idaho, and Nevada. We surveyed target and nearby alternate sites on public lands in southeastern Oregon where there was evidence that Columbia spotted frogs were historically present. We found the species at 59.5 percent (25 of 42) of target or nearby alternate sites. They were in 15 of 23 permanent streams and 8 of 13 intermittent streams. Our surveys do not provide evidence of widespread population losses in our sites. Interpretation of status of Columbia spotted frogs in this study is limited by a lack of precision in some of the historical locations and by our inability to determine if locations where only adults were indicated in the historical record once had breeding populations. Our results support the need for continued investigation of these populations.

Open-File Report↗
USGS2009

Short-term effect of cattle exclosures on Columbia Spotted Frog (Rana luteiventris) populations and habitat in northeastern Oregon

Livestock grazing is a common land use across the western United States, but concerns have been raised regarding its potential to affect amphibian populations. We studied the short-term effects of full and partial livestock grazing exclosures on Rana luteiventris (Columbia Spotted Frog) populations using a controlled manipulative field experiment with pre- and posttreatment data (2002–2006). Despite a significant increase in vegetation height within grazing exclosures, we did not find treatment effects for egg mass counts, larval survival, or size at metamorphosis 1–2 years following grazing exclosure installation. Water samples taken in late summer showed concentrations of nitrite, nitrate, ammonia, and orthophosphate that were low or near detection limits across all ponds and years. The results of this experiment do not support a hypothesis that limiting cattle access to breeding ponds will help conserve R. luteiventris populations in our study area. Further research is needed to evaluate regional variation and long-term effects of grazing exclosures on R. luteiventris populations.

Journal of Herpetology↗
USGS2008

A Protocol for Aging Anurans Using Skeletochronology

Age distribution information can be an important part of understanding the biology of any population. Age estimates collected from the annual growth rings found in tooth and bone cross sections, often referred to as Lines of Arrested Growth (LAGs), have been used in the study of various animals. In this manual, we describe in detail all necessary steps required to obtain estimates of age from anuran bone cross sections via skeletochronological assessment. We include comprehensive descriptions of how to fix and decalcify toe specimens (phalanges), process a phalange prior to embedding, embed the phalange in paraffin, section the phalange using a microtome, stain and mount the cross sections of the phalange and read the LAGs to obtain age estimates.

Open-File Report↗