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Papers & Reports Amphibian conservation in the Anthropocene
Authors: Evan HC Grant; Erin Muths; Benedikt R Schmidt; S Petrovan
Date: 2019-08 | Outlet: Biological Conservation 236 (2019) 543–547
Research is necessary to identify patterns in nature, to understand how a system functions, and to make predictions about the future state of an ecosystem. Applied research in conservation biology can identify effective strategies to maintain biodiversity, though many papers end with the conclusion that more research is needed. However, more research does not necessarily lead to solutions. We use the ongoing global decline of amphibians as a salient example to highlight limitations in current conservation research, and to focus on finding solutions which are directly relevant for conservation. While research has been conducted since declines were first detected in the 1990s, outside a few specific examples, little progress in conservation has been achieved. We suggest that the case of amphibian declines is relevant to conservation science in general, as the current paradigm for conservation is that management is planned after research is completed; research and management are not effectively (and not directly) connected. This disconnect illustrates the knowledge-action divide which has been noted recently as a serious deficiency in conservation. Accordingly, we use this introductory paper to the Special Issue (Amphibian conservation in the Anthropocene: Progress and challenges) to describe amphibians as a conservation dilemma, and to make the case for a different, more pragmatic, and more solutions-focused, view of conservation research.
Papers & Reports North-facing slopes and elevation shape asymmetric genetic structure in the range-restricted salamander Plethodon shenandoah
Authors: K P Mulder; N Cortes-Rodriguez; Evan HC Grant; A B Brand; R C Fleischer
Outlet: Ecology and Evolution
Species with narrow environmental preferences are often distributed across fragmented patches of suitable habitat, and dispersal among subpopulations can be difficult to directly observe. Genetic data collected at population centers can help quantify gene flow, which is especially important for vulnerable species with a disjunct range. Plethodon shenandoah is a Federally Endangered salamander known only from three mountaintops in Virginia, USA. To reconstruct the evolutionary history and population connectivity of this species, we generated both mitochondrial and nuclear data using sequence capture for all three populations and found strong population structure that was independent of geographic distance. Both the nuclear markers and mitochondrial genome indicated a deep split between the most southern population and the combined central and northern population. Although there was some mitochondrial haplotype-splitting between the central and northern populations, there was complete admixture in nuclear markers. This is indicative of either a recent split or current male-biased dispersal among mountain isolates. Models of landscape resistance found that dispersal across north-facing slopes at mid-elevation levels best explain the observed genetic structure among populations. These unexpected results highlight the importance of landscape features in understanding and predicting movement and fragmentation of salamanders across space.
Papers & Reports Disentangling effects of invasive species and habitat while accounting for observer error in a long-term amphibian study
Authors: J C Rowe; Adam Duarte; C A Pearl; B McCreary; S Galvan; J T Peterson; M J Adams
Date: 2019-04-02 | Outlet: Ecosphere
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 years 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 taxa 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.
Papers & Reports Drought-mediated extinction of an arid-land amphibian: insights from a spatially explicit dynamic occupancy model
Authors: E R Zylstra; D E Swann; Blake R Hossack; Erin Muths; R J Steidl
Outlet: Ecological Applications 29: e01859
Understanding how natural and anthropogenic processes affect population dynamics of species with patchy distributions is critical to predicting their responses to environmental changes. Despite considerable evidence that demographic rates and dispersal patterns vary temporally in response to an array of biotic and abiotic processes, few applications of metapopulation theory have sought to explore factors that explain spatio-temporal variation in extinction or colonization rates. To facilitate exploring these factors, we extended a spatially explicit model of metapopulation dynamics to create a framework that requires only binary presence-absence data, makes few assumptions about the dispersal process, and accounts for imperfect detection. We apply this framework to 22 years of biannual survey data for lowland leopard frogs, Lithobates yavapaiensis, an amphibian that inhabits arid stream systems in the southwestern U.S. and northern Mexico. Our results highlight the importance of accounting for factors that govern temporal variation in transition probabilities, as both extinction and colonization rates varied with hydrologic conditions. Specifically, local extinctions were more frequent during drought periods, particularly at sites without reliable surface water. Colonization rates increased when larval and dispersal periods were wetter than normal, which increased the probability that potential emigrants metamorphosed and reached neighboring sites. Extirpation of frogs from one watershed during a period of severe drought demonstrated the influence of site-level features, as frogs persisted only in areas where most sites held water consistently and where the amount of sediment deposited from high-elevation wildfires was low. Application of our model provided novel insights into how climate-related processes affected the distribution and population dynamics of an arid-land amphibian. The approach we describe has application to a wide array of species that inhabit patchy environments, can improve our understanding of factors that govern metapopulation dynamics, and can inform strategies for conservation of imperiled species.
Papers & Reports Batrachochytrium slamandrivorans (Bsal) in Appalachia: using scenario building to proactively prepare for a wildlife disease outbreak caused by an invasive amphibian chytrid fungus
Authors: M C Hopkins; M J Adams; P E Super; Deanna H Olson; C R Hickman; P English; L Sprague; I B Maska; A B Pennaz; K A Ludwig
Date: 2018-11-05 | Outlet: U.S. Geological Survey Open-File Report 2018-1150
Batrachochytrium salamandrivorans (Bsal), a pathogenic chytrid fungus, is nonnative to the United States and poses a disease threat to vulnerable amphibian hosts. The Bsal fungus may lead to increases in Threatened, Endangered, and Sensitive status listings at local, state, and federal levels, resulting in financial costs associated with implementing the Endangered Species Act . The U.S. is a global biodiversity hotspot for salamanders, an order of amphibians that is particularly vulnerable to developing a disease called chytridiomycosis when exposed to Bsal. Published Bsal risk assessments for North America have suggested that salamanders within the Appalachian region of the U.S. are at a high risk. In May 2017, a workshop was facilitated by the Department of the Interior?s (DOI) Strategic Sciences Group (SSG). A discussion-based incident-response exercise focused on a hypothetical Bsal disease outbreak in Appalachia was led by U.S. Geological Survey (USGS) staff members. Participants included representatives of the Eastern Band of the Cherokee Indians, the U.S. Fish and Wildlife Service (USFWS), National Park Service, Appalachian Landscape Conservation Cooperative, Tennessee Wildlife Resources Agency, and U.S. Department of Agriculture?s U.S. Forest Service. Scenario-building was utilized to brainstorm cascading consequences (social, economic and ecological) of a Bsal disease outbreak in this region of Appalachia. This report highlights the management and science actions that should could be undertaken to ensure an effective, rapid response to a Bsal introduction to the United States.
Papers & Reports Managing the trifecta of disease, climate, and contaminants: Searching for robust choices under multiple sources of uncertainty
Authors: K L Smalling; Collin A Eagles-Smith; R A Katz; Evan HC Grant
Date: 2019-05-30 | Outlet: Biological Conservation 236: 153-161
Amphibian populations are exposed to multiple stressors, with potential for synergistic effects. These synergies can increase uncertainty in our ability to characterize the effects of each stressor and to understand the degree to which their effects interact to impact population processes. This uncertainty challenges our ability to identify appropriate management alternatives. Finding solutions that are robust to these uncertainties can improve management when knowledge is absent or equivocal and identify critical knowledge gaps. Bayesian Belief Networks (BBNs) are probabilistic graphical models that explicitly account for various sources of uncertainty and are used increasingly by environmental practitioners because of their broad applicability to ecological risk assessments. BBNs allow the user to: 1) generate a conceptual model to link actions to outcomes, 2) use a variety of source data (empirical or expert opinion), 3) explore robust management strategies under uncertainty, 4) use sensitivity analysis to identify opportunities for developing new management actions, and 5) guide the design of data collection for monitoring to improve management decisions. BBNs contribute considerably to environmental research and management because they are transparent and treat uncertainty explicitly. Because of the high level of uncertainty in stressor response, we developed a BBN to conceptually evaluate the effects of potential management actions on amphibian populations exposed to disease, environmental contaminants, and increasingly frequent and severe droughts
Papers & Reports Timing of first and last calls and median calling peaks for Pseudacris crucifer, and of the first call for Hyla chrysoscelis/versicolor, at six wetlands in the St. Croix National Scenic Riverway from 2008-2012
Authors: W J Sadinski; M Roth
Date: 2018-09-06 | Outlet: U.S. Geological Survey data release,
To better understand relations of annual calling phenophases for Pseudacris crucifer, and of the first calls of the season for Hyla chrysoscelis/versicolor, to the timing of the start of the calling season, we compared these dynamics for six wetlands in the St. Croix National Scenic Riverway from 2008 to 2012. We installed an acoustic recorder at each site prior to the start of each calling season and programmed it to record for five minutes at the top of every hour until late summer. We then used the Songscape option in Songscope software to generate annual summaries of all acoustic files recorded at each site. We created contour plots of the summarized median dB values across bandwidths in each recording and then assessed individual calls and calling peaks by visually examining these plots to identify first (and last) calls via the unique call signatures for these two species. We examined individual five-minute recordings aurally and visually as necessary when sound images represented on the contour plots were confounded and to ensure that the calling peaks described below were dates when calling activity was relatively intense. We also determined the daily median dB levels for frequencies across 2900 to 3200 Hz during 2100 to 2300 h, the bandwidth that typically encompassed the primary energy peak in P. crucifer calls and a time period during which P. crucifer typically called most consistently throughout their calling season. We did this for each day from the date when P. crucifer first called during each year to the date when they last called during each year. Because calling activity could vary from one hour to the next, we integrated the area under the curve for the daily median dB levels from 2900 to 3200 Hz during 2100 to 2300 h. We removed dates when overlapping sounds from storms or other sources rendered comparisons to calls of P. crucifer inaccurate. We used the resultant set of integrands to represent the relative sound intensity (as an indicator of calling activity) for P. crucifer across those hours for each date. We then used these integrands to determine the three highest peak calling dates for this species and used the median of those three dates as the overall median peak date for each site in each year.
Papers & Reports The eight-day interval during which amphibians first called annually at individual study wetlands across four study areas.
Authors: W J Sadinski; M Roth
Date: 2018-09-06 | Outlet: U.S. Geological Survey data release,
To help determine when winter conditions were changing to spring conditions annually in our four study areas, we determined the first eight-day interval (in accordance with the scale limitations of satellite data we used to assess the presence of snow) during which the first amphibian of the season called at each of our study wetlands in those areas. To do this, we examined contour plots of summaries of all the acoustic data we collected at that site in a given year to identify the unique call signatures of individual amphibian species by date and time. When necessary due to potential confounding on a contour plot, we also examined relevant individual five-minute recordings aurally and visually to confirm whether a call occurred. When we confirmed the date of the first call we recorded in a given season, we identified the eight-day interval in which that date fell, with the first such interval beginning on January 1 of each year.
Papers & Reports Seasonal median daily water depths for study wetlands in the Tamarac National Wildlife Refuge, the St. Croix National Scenic Riverway, the North Temperate Lakes Long-term Research area, and the Upper Mississippi River study area from 2008-2012
Authors: W J Sadinski; M Roth
Date: 2018-09-06 | Outlet: U.S. Geological Survey data release,
To relate water levels in our study wetlands to temperature, precipitation, wetland water depth, and amphibian calling activity, we installed one pressure logger in the deepest spot we could find in each wetland. Soon after thawing conditions allowed, we drove a plastic pipe (anchor pipe) into the sediments at the deepest location and secured another pipe to it that contained one pressure logger (Global Water Model 14 and 15 [College Station, TX, USA] or Onset Computer Corporation Model U20-001-04 [Bourne, MA, USA]) suspended approximately 2.5 cm above the sediments. We installed additional individual pressure loggers in the upper part of the logger pipes (in air) at select locations to measure barometric pressure for calibrating the submerged loggers’ readings. We measured pressure once per hour and used software supplied by the logger manufacturers to upload and convert data to depth at the end of each season.
Papers & Reports Daily calling activity for Pseudacris crucifer at site SC4DAI2 in the St. Croix National Scenic Riverway from 2008 to 2012, as indicated by the results of integrating daily median dB values across 2900 to 3200 Hz and 2100 to 2300 h
Authors: W J Sadinski; M Roth
Date: 2018-09-06 | Outlet: U.S. Geological Survey data release,
To describe calling activity of Pseudacris crucifer in relation to temperature, precipitation, and wetland water levels, we programmed an acoustic recorder (Wildlife Acoustics) to sample seasonal amphibian calls remotely at study site SC4DAI2 in the St. Croix National Scenic Riverway from 2008 to 2012. We programmed the recorder to sample for five minutes at the top of every hour of every day from late winter/early spring through late summer. We used the Songscape option in Songscope software to generate annual summaries of all of our acoustic samples from SC4DAI2. These summaries included a median dB level for each prescribed frequency within each recording. Pseudacris crucifer, the spring peeper, inhabited SC4DAI2 and typically called over several weeks each year, depending upon weather conditions and surface-water availability. Most of the energy in their individual calls occurred between 2900 and 3200 Hz, which provided a unique acoustic signature compared with the other anurans that called from the site. We used this information as part of a case study to better understand how the daily calling activity of P. crucifer varied relative to air temperature, precipitation, and water depth at SC4DAI2 across years. We first determined the daily median dB levels for frequencies across 2900 to 3200 Hz during 2100 to 2300 h, a time period during which P. crucifer typically called throughout their calling season. We did this for each day from the date when P. crucifer first called each year to the date when they last called each year and considered any day in this range as one during which they potentially could call. Because calling activity could vary from one hour to the next, we integrated the area under the curve for the daily median dB levels from 2900 to 3200 Hz during 2100 to 2300 h. We removed dates when overlapping sounds from storms or other sources rendered comparisons to calls of P. crucifer inaccurate. We used the resultant set of integrands to represent the relative sound intensity (as an indicator of calling activity) for P. crucifer across those hours for each date. Those integrands are contained in this data set. These data enabled us to then compare daily integrand values with daily measurements of air temperature, precipitation totals, and water depth.
Papers & Reports Challenges in complementing data from ground-based sensors with satellite-derived products to measure ecological changes in relation to climate?lessons from temperate wetland-upland landscapes
Authors: A L Gallant; W J Sadinski; J Brown; G B Senay; M R Roth
Date: 2018-03-16 | Outlet: Sensors 18(3)880
Assessing climate-related ecological changes across spatiotemporal scales meaningful to resource managers is challenging because no one method reliably produces essential data at both fine and broad scales. We recently confronted such challenges while integrating data from ground- and satellite-based sensors for an assessment of four wetland-rich study areas in the U.S. Midwest. We examined relations between temperature and precipitation and a set of variables measured on the ground at individual wetlands and another set measured via satellite sensors within surrounding 4 km2 landscape blocks. At the block scale, we used evapotranspiration and vegetation greenness as remotely sensed proxies for water availability and to estimate seasonal photosynthetic activity. We used sensors on the ground to coincidentally measure surface-water availability and amphibian calling activity at individual wetlands within blocks. Responses of landscape blocks generally paralleled changes in conditions measured on the ground, but the latter were more dynamic, and changes in ecological conditions on the ground that were critical for biota were not always apparent in measurements of related parameters in blocks. Here, we evaluate the effectiveness of decisions and assumptions we made in applying the remotely sensed data for the assessment and the value of integrating observations across scales, sensors, and disciplines.
Papers & Reports Multi-year data from satellite- and ground-based sensors show details and scale matter in assessing climate's effects on wetland surface water, amphibians, and landscape conditions
Authors: W J Sadinski; A L Gallant; M Roth; J Brown; G Senay; W Brininger; P M Jones; J Stoker
Date: 2018-09-07 | Outlet: PLoS ONE 13(9): e0201951
Long-term, interdisciplinary studies of relations between climate and ecological conditions on wetland-upland landscapes have been lacking, especially studies integrated across scales meaningful for adaptive resource management. We collected data in situ at individual wetlands, and via satellite for surrounding 4-km2 landscape blocks, to assess relations between annual weather dynamics, snow duration, phenology, wetland surface-water availability, amphibian presence and calling activity, greenness, and evapotranspiration in four U.S. conservation areas from 2008 to 2012. Amid recent decades of relatively warm growing seasons, 2012 and 2010 were the first and second warmest seasons, respectively, dating back to 1895. Accordingly, we observed the earliest starts of springtime biological activity during those two years. In all years, early-season amphibians first called soon after daily mean air temperatures were ? 0°C and snow had mostly melted. Similarly, satellite-based indicators suggested seasonal leaf-out happened soon after snowmelt and temperature thresholds for plant growth had occurred. Daily fluctuations in weather and water levels were related to amphibian calling activity, including decoupling the timing of the onset of calling at the start of season from the onset of calling events later in the season. Within-season variation in temperature and precipitation also was related to vegetation greenness and evapotranspiration, but more at monthly and seasonal scales. Wetland water levels were moderately to strongly associated with precipitation and early or intermittent wetland drying likely reduced amphibian reproduction success in some years, even though Pseudacris crucifer occupied sites at consistently high levels. Notably, satellite-based indicators of landscape water availability did not suggest such consequential, intra-seasonal variability in wetland surface-water availability. Our cross-disciplinary data show how temperature and precipitation interacted to affect key ecological relations and outcomes on our study landscapes. These results demonstrate the value of multi-year studies and the importance of scale for understanding actual climate-related effects in these areas.
Papers & Reports Compounding effects of climate change reduce population viability of a montane amphibian
Authors: A M Kissel; W J Palen; M E Ryan; M J Adams
Date: 2018-12-27 | Outlet: Ecological Applications
Anthropogenic climate change presents challenges and opportunities to the growth, reproduction, and survival of individuals throughout their life cycles. Demographic compensation among life-history stages has the potential to buffer populations from decline, but alternatively, compounding negative effects can lead to accelerated population decline and extinction. In montane ecosystems of the US Pacific Northwest, increasing temperatures are resulting in a transition from snow-dominated to rain-dominated precipitation events, reducing snowpack. For ectotherms such as amphibians, warmer winters can reduce the frequency of critical minimum temperatures and increase the length of summer growing seasons, benefiting post-metamorphic stages, but may also increase metabolic costs during winter months, which could decrease survival. Lower snowpack levels also result in wetlands that dry sooner or more frequently in the summer, increasing larval desiccation risk. To evaluate how these challenges and opportunities compound within a species? life history, we collected demographic data on Cascades frog (Rana cascadae) in Olympic National Park in Washington state to parameterize stage-based stochastic matrix population models under current and future (A1B, 2040s and 2080s) environmental conditions. We estimated the proportion of reproductive effort lost each year due to drying using watershed-specific hydrologic models, and coupled this with an analysis that relates 15-years of R. cascadae abundance data with a suite of climate variables. We estimated the current population growth (λs) to be 0.98 (95% CI: 0.97-0.99), but predict that λs will decline under continued climate warming, resulting in a 62% chance of extinction by the 2080s because of compounding negative effects on early and late life history stages. By the 2080s, our models predict that larval mortality will increase by 17% as a result of increased pond drying, and adult survival will decrease by 7% as winter length and summer precipitation continue to decrease. We find that reduced larval survival drives initial declines in the 2040s, but further declines in the 2080s are compounded by decreases in adult survival. Our results demonstrate the need to understand the potential for compounding or compensatory effects within different life history stages to exacerbate or buffer the effects of climate change on population growth rates through time.
Papers & Reports Multistate occupancy modeling improves understanding of amphibian breeding dynamics in the Greater Yellowstone Area
Authors: W R Gould; A M Ray,; L L Bailey; D Thoma,; R Daley; K Legg
Outlet: Ecological Applications
Papers & Reports Time-to-detection Occupancy Modeling: An Efficient Method for Analyzing the Occurrence of Amphibians and Reptiles
Authors: Brian J Halstead; Patrick M Kleeman; Jonathan P Rose
Date: 2018-11-27 | Outlet: Journal of Herpetology 52:416-425
Occupancy models provide a reliable measure of species distributions while accounting for imperfect detectability. The cost of accounting for false absences is that occupancy surveys typically require repeated visits to a site or multiple-observer techniques. More efficient methods of estimating detection probabilities would allow more sites to be surveyed for the same effort, resulting in more information about the ecological processes leading to occupancy. Time-to-detection surveys allow the estimation of detection probability based on a single site visit by one observer, and therefore might be an efficient technique for herpetological occupancy studies. We evaluated the use of time-to-detection surveys to estimate the occupancy of pond-breeding amphibians at Point Reyes National Seashore, California, USA, including variables that affected detection rates and the probability of occurrence. We found that detection times were short enough and occupancy high enough to reliably estimate the probability of occurrence of three pond-breeding amphibians at Point Reyes National Seashore, and that survey and site conditions had species-specific effects on detection rates. In particular, relative abundance was negatively related to the time to initial detection of all species, and pond area was positively related to time to initial detection for Sierran Treefrogs (Hyliola sierra) and Rough-skinned Newts (Taricha granulosa). Rough-skinned newt time to initial detection also was affected by date, with lowest initial detection time in early summer. California Red-legged Frog (Rana draytonii) time to detection was lowest in ponds with a mean depth of 0.6 m, and higher in shallower and deeper ponds. Probability of occurrence of Sierran Treefrogs and Rough-skinned Newts was negatively related to the presence of fish and pond area. Rarely detected species required constraints on priors to fit time-to-detection models. Time-to-detection surveys can provide an efficient method of estimating detection probabilities and accounting for false absences in occupancy studies of reptiles and amphibians.
Papers & Reports Aquatic macroinvertebrate community response to wetland mitigation in the Greater Yellowstone Ecosystem
Authors: L K Swartz; Blake R Hossack; Erin Muths; R L Newell; W H Lowe
Date: 2019 | Outlet: Freshwater Biology 64: 942-953
Papers & Reports Effects of Persistent Energy-related Brine Contamination on Amphibian Abundance in National Wildlife Refuge Wetlands
Authors: Blake R Hossack; K L Smalling; Chauncey W Anderson; T Preston; I M Cozzarelli,; R K Honeycutt
Date: 2018 | Outlet: Biological Conservation 228:36–43
Papers & Reports Estimating the probability of movement and partitioning seasonal survival in an amphibian metapopulation
Authors: Erin Muths; L L Bailey; Brad A Lambert; S Schneider
Date: 2018-12 | Outlet: Ecosphere
Movement of individuals has been described as one of the best studied, but least understood concepts in ecology. The magnitude of movements, routes, and probability of movement, has significant application to conservation. Information about movement can inform efforts to model species persistence and is particularly applicable in situations where specific threats (e.g., disease) may depend on the movement of hosts and potential vectors. We estimated the probability of movement (breeding dispersal and permanent emigration) in a metapopulation of 16 breeding sites for boreal toads (Anaxyrus boreas boreas). We used a multi-state mark-recapture approach unique in its complexity (16 sites over 18 years) to address questions related to these movements and variation in resident survival. We found that individuals had a 1-2% probability of dispersing in a particular year and that approximately 10-20% of marked individuals were transient and observed in the metapopulation only once. Resident survival probabilities differed by season, with 71-90% survival from emergence from hibernation through early post-breeding and > 97% survival from mid/late active season through hibernation. Movement-related probabilities are needed to predict species range expansions and contractions, estimate population and metapopulation dynamics, understand host-pathogen and native-invasive species interactions, and to evaluate the relative effects of proposed management actions.
Papers & Reports Late-season movement and habitat use by Oregon Spotted Frog (Rana pretiosa in Oregon, USA
Authors: C A Pearl; B McCreary; J C Rowe; M J Adams
Date: 2018-09-27 | Outlet: Copeia
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 9 sites from 4 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 specialized 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. DistinctiveSpecialized 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.
Authors: P E Howell; Brent H Sigafus; Blake R Hossack; Erin Muths
Outlet: Southwestern Naturalist 64:69-72
Invasive species are a major threat to the persistence of native species, particularly in systems where ephemeral aquatic habitats have been converted to or replaced by permanent water and predators such as fish have been introduced. Within the Altar Valley, Arizona, USA, the invasive American bullfrog (Lithobates [=Rana] catesbeianus) has been successfully eradicated to help recover Chiricahua leopard frogs (Lithobates chiricahuensis). However, other non-native predators including sunfish (Lepomis spp) are present in some permanent water bodies. During four consecutive years (2014-2017) we detected both the federally-threatened Chiricahua leopard frog and sunfish at one permanent water body in the Altar Valley. This suggests that despite the potential negative effect of predatory fish on amphibians, there may be conditions where the Chiricahua leopard frog may be able to co-occur with this non-native predator. A better understanding of rare situations of co-occurrence with non-native predators may contribute to our understanding of why co-occurrence happens in some but not all systems and whether conservation strategies can be developed in situations where complete eradication of non-native predators is infeasible.