Search ARMI Database

Complex, interactive ecological constraints regulate species distributions, and understanding these factors is crucial for predicting species persistence. We used occupancy analysis, which corrects for imperfect detection, to test the importance of abiotic and biotic habitat and landscape factors on probability of occupancy by boreal chorus frog (Pseudacris maculata; Agassiz 1850) tadpoles. We hypothesized that hydropattern and predators are primarily important as they affect desiccation and predation risk and can interact in ways difficult to predict. We surveyed 62 wetland sites across an elevational gradient in Colorado, USA and modeled patterns in P. maculata occupancy. Tadpoles were most frequently present in intermediate hydropattern systems with lower desiccation risk and no predatory fish due to occasional drying. P. maculata occupancy had a strong negative relationship with fish presence while tadpoles, odonate larvae and tiger salamanders (Ambystoma mavortium; Baird 1850) frequently co-occurred. Dry seasonal conditions will likely result in fewer intermediate hydropattern ponds available for amphibian breeding. We hypothesize that this will force P. maculata to breed in habitats with fish. As habitats shrink, predators that co-occur with P. maculata are expected to concentrate in the remaining habitat and increase predation risk for developing tadpoles (assuming predators are similarly constricted in their habitat use as amphibians are).

Among the multiple stressors potentially affecting the presence of amphibians across agricultural landscapes, habitat loss and exposure to pesticides are likely primary factors contributing to amphibian decline. Conservation efforts have attempted to restore wetlands lost through landscape modifications with the aim of reducing contaminant loads in surface waters and providing quality habitat to wildlife. However, the benefits of this increased wetland area, perhaps especially for amphibians, may be negated if habitat quality is insufficient to support persistent populations. We examined the presence of pesticides and nutrients in water and sediment as indicators of habitat quality and assessed the accumulation of pesticides in tissue of two native amphibian species Pseudacris maculata (chorus frogs) and Lithobates pipiens (leopard frogs) at six wetlands (3 restored and 3 reference) in Iowa, USA. Restored wetlands are positioned on the landscape to receive subsurface tile drainage water while reference wetlands receive water from overland run-off and shallow groundwater sources. Concentrations of the pesticides frequently detected in water and sediment samples were not different between wetland types. The herbicide atrazine was detected in 100% of the water samples and in some instances at concentrations high enough to potentially cause reproductive effects in leopard frogs. Nutrient concentrations were higher in the restored wetlands but lower than concentrations thought to cause lethality in frogs. Seventeen pesticides were detected in tissue samples with concentrations ranging from https://0.08 to 1,500 µg/kg wet weight. No significant differences in pesticide concentrations were observed between species, although concentrations tended to be higher in leopard frogs compared to chorus frogs, possibly because of differences in life histories. Our results provide information on habitat quality in restored wetlands that will assist state and federal agencies, landowners, and resource managers in identifying and implementing conservation and management actions for these and similar wetlands in agriculturally dominated landscapes.

Estimating demographic parameters like survival or recruitment provides insight into the state and trajectory of populations, but understanding the contexts influencing those parameters, including both biotic and abiotic factors, is particularly important for management and conservation. At a high elevation national park in Central Spain, common toads (Bufo bufo) are apparently taking advantage of the near-extirpation of the midwife toad (Alytes obstetricans), as colonizationinto new breeding ponds is evident.Within this scenario, we expected demographic parameters of common toad populations to be affected favorably by the putative release from competition. However, we found the population growth rate was negative in 4 of 5 years at the long-standing population; survival probability at the long-standing population and newly-colonized breeding ponds was lower than reported for other toads living at high elevations and the probability of recruitment was inadequate to compensate for the survival rate in maintaining a positive trajectory for either of the breeding ponds. We assessed weather covariates and disease for their contribution to the context thatmay be limiting the common toad’s successful use of the niche vacated by the midwife toad.

The Des Moines Lobe of central Iowa has undergone drastic land-use changes over the last two centuries, with 90% of the state’s wetlands converted primarily by agricultural practices and urban development. The introduction of tile drainage to improve land for agriculture facilitated this conversion and still contributes to the productivity of this agricultural landscape. Consequently, natural wetland habitat has become rare and fragmented, affecting species with limited mobility, such as amphibians. Amphibians are an important component of these wetland systems where they provide food for other animals and eat copious amounts of insects. However, many amphibian species are at risk world-wide and some are at risk in Iowa.

While loss of habitat is the main reason behind amphibian decline, in the Des Moines Lobe, amphibians are further challenged by an environment potentially compromised by contaminants and their limited mobility exacerbates the effects of habitat fragmentation.

In response to observed ecosystem degradation in environmentally sensitive areas the USDA introduced the Conservation Reserve Enhancement Program (CREP) to target high-priority conservation issues. In the year 2001, the state of Iowa partnered with USDA and developed a CREP to strategically locate and restore wetlands on private land that receive run-off from multiple sub-surface tile drains to help reduce the export of nitrates from agricultural watersheds before the water reaches the Mississippi River and the Gulf of America. Although CREP wetlands are intended primarily to reduce nitrogen to protect drinking water and reduce hypoxia in the Gulf of America, they provide other ecosystem services such as providing wildlife habitat and recreational opportunities. For example, CREP wetlands and their adjoining grass buffers provide forage and cover for waterfowl and upland game.

For complete article, see here: https://www.fort.usgs.gov/science-feature/890

Quantitative evaluations of reintroductions are infrequent and assessments of milestones reached before a project is completed, or abandoned due to lack of funding, are rare. However, such assessments, which are promoted in adaptive management frameworks, are critical. Quantification can provide defensible estimates of biological success, such as the number of survivors from a released cohort, with associated cost per animal. It is unlikely that the global issues of endangered wildlife and population declines will abate, therefore, assurance colonies and reintroductions are likely to become more common. If such endeavors are to be successful biologically or achieve adequate funding, implementation must be more rigorous and accountable. We use a novel application of a multistate, robust design capture-recapture model to estimate survival of reintroduced tadpoles through metamorphosis (i.e., the number of individuals emerging from the pond) and thereby provide a quantitative measure of effort and success for an “in progress” reintroduction of toads. Our data also suggest that tadpoles released at later developmental stages have an increased probability of survival and that eggs laid in the wild hatched at higher rates than eggs laid by captive toads. We illustrate how an interim assessment can identify problems, highlight successes, and provide information for use in adjusting the effort or implementing a Decision-Theoretic adaptive management strategy.

ARMI scientists Evan Grant and Erin Muths, teamed with David Miller (former ARMI post doc and now professor at Pennsylvania State University) to produce the proposal that was selected for Powell Center Support for 2014-2015. The Powell Center is a USGS center that facilitates the development of new and innovative processes by which scientific understanding can be applied to significant and complex issues in a unique setting for analysis and data synthesis.

The proposal moves forward from the recently published paper describing the magnitude of amphibian declines in the U.S. (Adams et al. 2013), and will now examine the mechanisms of decline using a data driven, but model-based, approach. Though focused on North America, the insights will be applicable to other systems and will lay the foundation for a larger, perhaps international, assessment of mechanisms behind global amphibian declines.

The 15 member working group includes not only ARMI scientists and data collected over the last 10 years, but others with long-term data on amphibians including scientists from Canada, Mexico and Europe. The first working group meeting will be held in Fort Collins in January 2014. A hallmark of the Powell Center is that it is "a scientist-driven institution where leveraging existing research efforts produces powerful new insights and moves scientific understanding and its inclusion into management forward at an accelerated pace."

Proposal abstract:

Amphibian populations are declining globally at unprecedented rates but statistically rigorous identification of mechanisms is lacking. Identification of reasons underlying large-scale declines is imperative to plan and implement effective conservation efforts. Most research on amphibian population decline has focused on local populations and local factors. However, the ubiquity of declines across species and landscapes suggests that causal factors at a broader scale are also important. Elucidation of the mechanisms driving population change has lagged, mainly because data have been unavailable at continental scales.

We propose to address this need by assembling data to answer questions about broad-scale drivers of amphibian decline. We will examine alterations in timing and availability of surface-water habitat (driven principally by climate change), as first order variables that control the probabilities of breeding, successful metamorphosis, and return rates of amphibians. Climate change (and its influence on shifting temperatures) is also correlated with other agents of decline such as disease and amplification of cyclical population dynamics; we consider these second-order effects.

Furthermore, data on other causal mechanisms are not available at broad-scales. We will use monitoring data (core data from USGS Amphibian Research and Monitoring Initiative, supplemented by data from collaborators in Canada, the U.S., and Mexico) and state-of-the-art statistical techniques to examine broad-scale mechanisms associated with changes in amphibian occupancy.

We will develop hypotheses for climate-induced shifts in occupancy dynamics, and test these hypotheses using a dataset representing many individual projects and regions from across North America. We will formulate the problem in hierarchical Bayesian models to examine multi-scale processes affecting patterns of species occupancy. This analysis of population trends across multiple spatial scales will facilitate the first rigorous quantitative examination of mechanisms affecting occupancy of amphibians across North America, and provide a continent-wide assessment of the contribution of climate-related factors to declines in amphibian populations. Hypotheses and methods developed through this collaborative effort will be useful in other locations experiencing amphibian declines (e.g., Australia, Europe) and our modeling approach will be useful for assessments of other taxa.

Associated PDF: http://dx.plos.org/10.1371/journal.pone.0064347

Welcome to the inaugural issue of ARMI’s Annual Update. This update provides highlights and significant milestones of this innovative program. ARMI is uniquely qualified to provide research and monitoring results that are scalable from local to national levels, and are useful to resource managers. ARMI has produced nearly 400 peer-reviewed publications, including 18 in 2011. Some of those publications are highlighted in this fact sheet. ARMI also has a new Website (http://armi.usgs.gov). You can now use it to explore an up-to-date list of ARMI products, to find summaries of research topics, to search for ARMI activities in your area, and to obtain amphibian photographs. ARMI’s annual meeting was organized by Walt Sadinski, Upper Midwest Environmental Science Center, and held in St Louis, Missouri. We met with local scientists and managers in herpetology and were given a tour of the herpetology collection at the St. Louis Zoo.

Full text: http://armi.usgs.gov/docs/ARMI%202011%20Annual%20Update.pdf (PDF*)

Widespread amphibian declines and habitat fragmentation, coupled with advancements in tracking technology, have sparked increased emphasis on studying movements and the use of terrestrial habitats by amphibians. Peñalara Natural Park, Sierra de Guadarrama, Central Spain, provides habitat for a number of amphibians that use upland sites. In response to increased pressure on habitat in this region by tourism, we used 4 months of radio telemetry data for 17 adult Common Toads (Bufo bufo) to characterize the terrestrial movements, assess the factors influencing these movements, and determine the distribution and cover characteristics of summer refugia for these toads. We found that: a) movements were most pronounced following the breeding season in June and adults made movements of up to 470 m away from breeding sites, b) movements were not influenced by basin size, climatic variables or the sex the individual, c) the amount of terrestrial habitat used by toads ranged from 245 m2 to 2.5 ha, and d) within these areas toads most often used rock piles and juniper patches (Juniper communis nana) as cover during the summer. Our study emphasizes the importance of considering terrestrial landscapes when developing conservation strategies, and we suggest that a buffer of minimal development extending 550 m from the shoreline of each natal pond be considered when conservation plans are developed for Common Toad habitat in Peñalara.

Prevalence of the amphibian chytrid fungus on Buenos Aires National Wildlife Refuge is low. Very few bullfrogs (a carrier of Bd) on the refuge test positive and very few Chiricahua Leopard Frogs test positive (only at sites off of the refuge). Bullfrogs have been nearly eradicated from the refuge, but because they carry the disease, there is potential for bullfrogs to act as a vector, carrying the disease to the Chiricahua Leopard Frogs which are an endangered species if they move back onto the refuge.

Breeding is limited by energetic or environmental constraints and long-lived species sometimes skip breeding opportunities. Environmental conditions may vary considerably across the geographic and elevational range of a species and species that can respond through variation in life history strategies are likely to maintain populations at the extremes of their ranges. The decision to skip breeding enables animals to adjust life history to circumstances, and plasticity in behavior allows implementation of adjustments. Elevational patterns suggest that breeding may be limited physiologically at high elevations (e.g., greater probability of skipped breeding; resources and environmental conditions more variable) in contrast to low elevations (probability of skipping breeding lower; resources and environmental conditions more predictable). We estimated the probabilities of survival and skipped breeding in a high-elevation population of Common Toads and compared estimates to existing data for Common Toads at low elevations, and to another toad species inhabiting a similar high elevation environment. Female Common Toads at high elevations tend to have high probabilities of skipping breeding and survival relative to data for Common Toads at low elevations, and appear to use a similar strategy of skipping breeding in response to similar environmental constraints as other toads at high elevations. We provide evidence of variability in this aspect of life history for Common Toads. Understanding variation in life history within widely distributed species is critical. Knowing that certain life history strategies are employed on a continuum informs conservation efforts, especially as impacts of climate change are likely to be different depending on elevation.

Though a third of amphibian species worldwide are thought to be imperiled, existing assessments simply categorize extinction risk, providing little information on the rate of population losses. We conducted the first analysis of the rate of change in the probability that amphibians occupy ponds and other comparable habitat features across the United States. We found that overall occupancy by amphibians declined 3.7% annually from 2002 to 2011. Species that are Red-listed by the International Union for Conservation of Nature (IUCN) declined an average of 11.6% annually. All subsets of data examined had a declining trend including species in the IUCN Least Concern category. This analysis suggests that amphibian declines may be more widespread and severe than previously realized.

More than 25 years ago, scientists began to identify unexplained declines in amphibian populations around the world. Much has been learned since then, but amphibian declines have not abated and the interactions among the various threats to amphibians are not clear. Amphibian decline is a problem of local, national, and international scope that can affect ecosystem function, biodiversity, and commerce. This fact sheet provides a snapshot of the state of the amphibians and introduces examples to illustrate the range of issues in the United States.

This story first appeared at http://www.fort.usgs.gov/Blackrock/ as a science feature for the Fort Collins Science Center.

 Amphibian decline is a problem of global importance, with over 40 percent of species considered at risk. This phenomenon is not limited to the tropics or to other countries; amphibian species in the United States are also declining, contributing to the larger global phenomenon. For example, in Wyoming, the Wyoming toad has been extirpated in the wild and the boreal toad is a species of special concern. Habitat loss (especially of wetlands) and disease are two examples of perturbations contributing to amphibian decline. 

Wetlands harbor a variety of wildlife from large ungulates to amphibians the size of a U.S. quarter. Because many amphibians depend on wetlands for breeding, feeding, and rearing young, the availability of wetlands is important to maintaining amphibian diversity and presence across suitable habitat.

Amphibian Research in Wyoming In northwestern Wyoming, scientist Erin Muths (U.S. Geological Survey, Fort Collins Science Center) has been leading a team of researchers investigating amphibian decline at a study site on the Blackrock Ranger Station compound on the Bridger-Teton National Forest. The work began in 2003, when Dr. Muths and David Pilliod (USGS Forest and Range Ecosystem Science Center) were awarded competitive funding from the USGS Amphibian Research and Monitoring Initiative (ARMI). The research team of Dr. Muths, Dr. Pilliod, and Drs. Steve Corn and Blake Hossack (USGS Northern Rocky Mountain Science Center) collaborates with the U.S. Forest Service (USFS) and other entities to study population demographics and disease ecology for the four species of amphibians that reside on the USFS Blackrock compound.

The Blackrock research site focused initially on an oxbow pond separated from the Buffalo Fork River by levees, where boreal toads (Anaxyrus boreas), Columbia spotted frogs (Rana luteivensis), chorus frogs (Pseudacris maculata), and tiger salamanders (Ambystoma tigrinum) were breeding. However, natural and human-made changes to the immediate landscape have caused concomitant changes to breeding habitat and increased the scope of the research.

 Construction on Wyoming Highway 26/U.S. Highway 287, which disturbed existing wetlands, included establishing a mitigation site (as required by federal and state laws). The mitigation site, located on the USFS Blackrock compound near the existing research site, may prove more valuable to amphibians than first thought. Heavy, late-spring runoff in 2011 and 2012 breached the levees between the oxbow and the river. These natural events are thought to have wiped out amphibian breeding efforts at the oxbow, leaving reproduction at the mitigation site as the only viable effort in these years. As a result, after only two years since establishment, two of the four species of amphibians that bred in the oxbow are using the mitigation site to breed.

 In the Rocky Mountains, the timing of amphibian reproduction is linked to the timing of snowmelt and subsequent spring runoff. These springtime events are likely to be affected by climate change, which in turn can influence wetland availability and persistence. Wetlands (both natural and constructed, like those established through mitigation efforts) are vital to the reproduction and persistence of amphibians across the landscape. Understanding climate dynamics in relation to wetland availability is an important component of managing landscapes that provide habitat for a wide diversity of wildlife, from large ungulates to toads to macroinvertebrates. 

Collaboration Is Key:

Collaborative research among USGS scientists, the Northern Rockies Conservation Cooperative, and the USFS has been funded for 3 years by the Wyoming Highway Department (WYDOT). This research effort will assess mitigation sites and natural sites to compare differences in habitat (physical site characteristics), demographics of the amphibian species, insect communities, disease presence and impact, and amphibian occupancy across the immediate landscape. Our goals are to track multiple populations of amphibians over time to better understand population-level host-pathogen dynamics, assess potential shifts in occupancy across the landscape, and determine the efficacy of the mitigation efforts at Blackrock. Results of the investigation will support Forest Service management of the amphibians and help refine protocols for future mitigation efforts required of WYDOT.

USGS research over the last 10 years has contributed to our understanding of site characteristics and the population dynamics of the boreal toad, providing information that is critical to the expanded project detailed above. For example, our previous data indicate that the boreal toad population at Blackrock is declining at 5–6 percent per year, and that disease due to the amphibian chytrid fungus (Batrachochytrium dendrobatidis) is contributing to this decline (Muths et al. 2008, Pilliod et al. 2010, Murphy et al. 2009, 2011). This fungal disease is not unique to Wyoming but is affecting amphibian populations worldwide. However, we’ve also shown that the Blackrock toad population is not crashing as has been the fate of some other boreal toad populations in the western United States (e.g., Muths et al. 2003). In fact, at some level the population is compensating for poor survival by increasing recruitment (Muths et al. 2011).

In addition, the value of our early data on boreal toads and chorus frogs will be increased by complementary data on salamanders and Columbia spotted frogs. Including other amphibian species will allow us to unravel connections among species and examine disease resistance, the roles of species as vectors, and competition.

In a larger context, understanding how amphibians (1) use previous natural habitat and mitigation sites and (2) shift demographically in response to disease will inform their conservation. As climate change affects amphibian habitat, especially wetlands, detailed information about assemblages of amphibians in their natural habitat becomes even more important. The USGS research team’s work at the Blackrock site is poised to contribute to these efforts.

References Corn, P.S., E. Muths, and D.S. Pilliod. 2011. Long-term observations of boreal toads at an ARMI apex site. Pages 101–104 in Andersen, C., ed. Questioning Greater Yellowstone’s future: Climate, land use, and invasive species. Proceedings of the 10th Biennial Scientific Conference on the Greater Yellowstone Ecosystem. October 11–13, 2010, Yellowstone National Park. Yellowstone National Park, WY, and Laramie, WY: Yellowstone Center for Resources and University of Wyoming William D. Ruckelshaus Institute of Environment and Natural Resources.

Murphy, P.J., S. St-Hilaire, S. Bruer, P.S. Corn, and C.R. Peterson. 2009. Distribution and pathogenicity of Batrachochytrium dendrobatidis in boreal toads from the Grand Teton area of western Wyoming. EcoHealth 6: 109–120.

Murphy, P.J., S. St-Hilaire and P.S. Corn. 2011. Temperature hydric environment, and prior pathogen exposure alter the experimental severity of chytridiomycosis in boreal toads. Diseases of Aquatic Organisms 95: 31–42, doi: 10.3354/dao02336.

Muths, E., P.S. Corn, A.P. Pessier and D.E. Green. 2003. Evidence for disease related amphibian decline in Colorado. Biological Conservation110 (2003): 357–365.

Muths, E., D.S. Pilliod, and L. Livo. 2008. Distribution and environmental limitations of an amphibian pathogen in the Rocky Mountains, USA. Biological Conservation 141: 1484–1492.

Muths, E., D.S. Pilliod, and R.D. Scherer. 2011. Compensatory effects of recruitment and survival on population persistence. Journal of Applied Ecology48: 873–879.

Pilliod, D.S., E. Muths, R.D. Scherer, P.E. Bartelt, P.S. Corn, B.R. Hossack, B.A. Lambert, R. McCaffery, and C. Gaughan. 2010. Effects of amphibian chytrid fungus on individual survival probability in wild boreal toads. Conservation Biology24: 1259 –1267

The ability to track individual animals is crucial in many field studies and often requires applying marks to captured individuals. Toe clipping has historically been a standard marking method for wild amphibian populations, but more recent marking methods include visual implant elastomer and photo identification. Unfortunately, few studies have investigated the influence and effectiveness of marking methods for recently metamorphosed individuals and as a result little is known about this life-history phase for most amphibians. Our focus was to explore survival probabilities and mark retention and migration in postmetamorphic Boreal Chorus Frogs (Psuedacris maculata) in a laboratory setting. Three treatments were assigned randomly among 147 individuals: frogs were either marked with visual implant elastomer, toe clipped, or left unmarked as controls. Growth and mortality were recorded for one year and resulting data were analyzed using known-fate models in Program MARK. Model selection results suggested that survival probabilities of frogs varied with time and showed some variation among marking treatments. We found that frogs with multiple toes clipped on the same foot had lower survival probabilities than individuals in other treatments, but individuals can be marked by clipping a single toe on two different feet without any mark loss or negative survival effects. Individuals treated with visual implant elastomer had a mark migration rate of 4% and mark loss rate of 6% and also showed very little negative survival impacts relative to control individuals.

This is the 2011 annual report for the Amphibian Research and Monitoring Initiative. It includes publication updates and a summary of amphibian monitoring trends.

Habitat fragmentation and the associated reduction in connectivity between habitat patches are commonly cited causes of genetic differentiation and reduced genetic variation in animal populations. We used eight microsatellite markers to investigate genetic structure and levels of genetic diversity in a relict population of wood frogs (Lithobates sylvatica) in Rocky Mountain National Park, Colorado. We also estimated migration rates among subpopulations, tested for a pattern of isolation-by-distance, and looked for evidence of a recent population bottleneck. The results from the clustering algorithm in Program STRUCTURE indicated the population is partitioned into two genetic clusters (subpopulations), and an estimate of FST (FST = 0.0675, P-value < 0.0001) also supports the genetic differentiation of the two clusters. Migration rates among the two subpopulations were small. Though we found support for a pattern of genetic isolation-by-distance, other processes also may have affected levels of genetic differentiation. Genetic variability in the population is low relative to other studies. However, we found no evidence that a recent bottleneck was responsible for the low variation. Conservation of the population of wood frogs would be improved by increasing the spatial distribution of the population and improving gene flow between the subpopulations. Construction or restoration of wetlands in the landscape between the clusters has the potential to address each of these objectives.

Understanding the relationship between climate-driven habitat conditions and survival is key to preserving biodiversity in the face of rapid climate change. Hydroperiod—the length of time water is in a wetland—is a critical limiting habitat variable for amphibians as larvae must metamorphose before ponds dry. Changes in precipitation and temperature patterns are affecting hydroperiod globally, but the impact of these changes on amphibian persistence is poorly understood. We studied Boreal Chorus Frog (Pseudacris maculata) tadpole response to simulated hydroperiods (i.e. water level reductions) in the laboratory using individuals collected from ponds spanning a range of natural hydroperiods (Colorado Front Range, USA). To assess the effects of experimental hydroperiod reduction, we measured mortality, time to metamorphosis, and size at metamorphosis. We found that tadpoles grew at rates reflecting the hydroperiods of their native ponds, regardless of experimental treatment. Tadpoles from permanent ponds metamorphosed faster than those from ephemeral ponds across all experimental treatments, a pattern which may represent a predation selection gradient or countergradient variation in developmental rates. Size at metamorphosis did not vary across experimental treatments. Mortality was low overall but varied by pond of origin. Our results suggest that adaptation to local hydroperiod and/or predation and temperature conditions is important in P. maculata. Moreover, the lack of a plastic response to reduced hydroperiods suggests that P. maculata may not be able to metamorphose quickly enough to escape drying ponds. These results have important implications for amphibian persistence in ponds predicted to dry more quickly due to rapid climate change.

Variation in the occurrence and abundance of species across landscapes has traditionally been attributed to processes at fine spatial scales (i.e., local conditions), but processes that operate across larger spatial scales such as seasonal migration or dispersal are also important. Recognition of the importance of processes that operate at broad, as well as fine, scales is growing. We evaluated hypothesized relationships between the probability of occupancy in wetlands by wood frogs (Lithobates sylvaticus) and boreal chorus frogs (Pseudacris maculata) during the breeding season and attributes of the landscape measured at three spatial scales in Rocky Mountain National Park, Colorado. We also used cost-based buffers and least-cost distances to derive estimates of landscape attributes at the broader spatial scales represented by seasonal movement and dispersal. Occupancy by breeding wood frogs was associated positively with the amount of streamside habitat adjacent to a wetland and associated negatively with the cost-based distance to the nearest occupied wetland. Occupancy by boreal chorus frogs was associated positively with the number of neighboring, occupied wetlands. We found little evidence that occupancy was correlated with fine-scale attributes measured at the wetlands.

Much attention has been given to the conservation of small populations, those that are small because of decline and those that are naturally small. Small populations are of particular interest because ecological theory suggests that they are vulnerable to the deleterious effects of environmental, demographic, and genetic stochasticity as well as natural and human induced catastrophes. However, testing theory and developing applicable conservation measures for small populations is hampered by sparse data. This lack of information is frequently driven by computational issues with small data sets that can be confounded by the impacts of stressors. We present estimates of demographic parameters from a small population of boreal toads that has been surveyed since 2001 using capture-recapture methods. Estimates of annual adult survival probability are high relative to other boreal toad populations, while estimates of recruitment rate are low. Despite using simple models, clear patterns emerged from the analyses suggesting that population size is constrained by low recruitment of adults and is declining slowly. These patterns provide insights that are useful in developing management directions for this small population and this study serves as an example of the potential for small populations to yield robust and useful information despite sample size constraints.