Demography of common toads after local extirpation of
Authors: Bosch J, Fernandez-Beaskoetxez S, Scherer R D, Amburgey S M, Muths E | Date: 2014-09 | Outlet: Amphibia-Reptilia | Format: .PDF
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.
Partitioning the non-consumptive effects of predators on prey with complex life histories
Authors: Davenport M, Hossack BR, Lowe WH | Date: 2014-08 | Outlet: Oecologia 176:149–155
Non-consumptive effects (NCE) of predators on prey can be as strong as consumptive effects and may be driven by numerous mechanisms, including predator characteristics. Previous work has highlighted the importance of predator characteristics in predicting NCEs, but has not addressed how complex life histories of prey could mediate predator NCEs. We conducted a meta-analysis to compare the effects of predator gape limitation (gape-limited or not) and hunting mode (active or sit-and-pursue) on the activity, larval period, and size at metamorphosis on larval aquatic amphibians and invertebrates. Larval prey tended to reduce their activity and require more time to reach metamorphosis in the presence of all predator functional groups, but the responses did not differ from zero. Prey metamorphosed at smaller size in response to non-gape-limited, active predators, but counter to expectations, prey metamorphosed larger when confronted by non-gape-limited, sit-and-pursue predators. These results indicate NCEs on larval prey life history can be strongly influenced by predator functional characteristics. More broadly, our results suggest that understanding predator NCEs would benefit from greater consideration of how prey life-history attributes mediate population and community-level outcomes.
Animal reintroductions: an innovative assessment of survival
Authors: Muths E, Bailey LL, Watry MK | Date: 2014-06 | Outlet: Biological Conservation xx:xxx-xxx
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 2013 Annual Update
Authors: Halstead BJ, Adams MJ, Grant ECH, Hossack BR, Smalling KL, Ball LC | Date: 2014-02-17 | Format: .PDF
Welcome to the 2013 Annual ARMI Update, which provides highlights and significant milestones of this innovative program. This was an especially notable year for ARMI with the release of a landmark publication “Trends in amphibian occupancy in the United States.” Our synthesis and scaling up of 9 years of monitoring data produced the first-ever estimate of how fast frogs, toads and salamanders in the United States are disappearing from their habitats. Our findings received international attention and rekindled the discussion about global amphibian declines. This was not the only topic we addressed this year, as ARMI’s total publication count rose to 460 papers representing our latest research findings on the effects of climate change, land use, diseases, pesticides, and management on amphibian populations.
Full text: armi.usgs.gov/docs/ARMI%202013%20Annual%20Update.pdf
Population declines lead to replicate patterns of internal range structure at the tips of the distribution of the California red-legged frog (Rana draytonii)
Authors: Richmond JQ, Backlin AR, Tatarian PJ, Solvesky BG, Fisher RN | Date: 2014 | Outlet: Biological Conservation | Format: .PDF
Demographic declines and increased isolation of peripheral populations of the threatened California red-legged frog(Rana draytonii)have led to the formation of internal range boundaries at opposite ends of the species’ distribution. While the population genetics of the southern internal boundary has been studied in some detail, similar information is lacking for the northern part of the range. In this study, we used microsatellite and mtDNA data to examine the genetic structuring and diversity of some of the last remaining R. draytonii populations in the northern Sierra Nevada, which collectively form the northern external range boundary. We compared these data to coastal populations in the San Francisco Bay Area, where the species is notably more abundant and still exists throughout much of its historic range. We show that ‘external’ Sierra Nevada populations have lower genetic diversity and are more differentiated from one another than their ‘internal’ Bay Area counterparts. This same pattern was mirrored across the distribution in California, where Sierra Nevada and Bay Area populations had lower allelic variability compared to those previously studied in coastal southern California. This genetic signature of northward range expansion was mirrored in the phylogeography of mtDNA haplotypes; northern Sierra Nevada haplotypes showed greater similarity to haplotypes from the south Coast Ranges than to the more geographically proximate populations in the Bay Area. These data cast new light on the geographic origins of Sierra Nevada R. draytonii populations and highlight the importance of distinguishing the genetic effects of contemporary demographic declines from underlying signatures of historic range expansion when addressing the most immediate threats to population persistence. Because there is no evidence of contemporary gene flow between any of the Sierra Nevada R. draytonii populations, we suggest that management activities should focus on maintaining and creating additional ponds to support breeding within typical dispersal distances of occupied habitat.
Modeling structured population dynamics using data from unmarked individuals
Authors: Zipkin, EF, Thorson, JT, See, K, Lynch, HJ, Grant, EHC, Kanno, Y, Chandler, RB, Letcher, BH, Royle, JA | Outlet: Ecology
The study of population dynamics requires unbiased, precise estimates of
abundance and vital rates that account for the demographic structure inherent in all wildlife
and plant populations. Traditionally, these estimates have only been available through
approaches that rely on intensive capture–recapture data. We extended recently developed Nmixture
models to demonstrate how demographic parameters and abundance can be estimated
for structured populations using only stage-structured count data. Our modeling framework
can be used to make reliable inferences on abundance as well as recruitment, immigration,
stage-specific survival, and detection rates during sampling. We present a range of simulations
to illustrate the data requirements, including the number of years and locations necessary for
accurate and precise parameter estimates. We apply our modeling framework to a population
of northern dusky salamanders (Desmognathus fuscus) in the mid-Atlantic region (USA) and
find that the population is unexpectedly declining. Our approach represents a valuable
advance in the estimation of population dynamics using multistate data from unmarked
individuals and should additionally be useful in the development of integrated models that
combine data from intensive (e.g., capture–recapture) and extensive (e.g., counts) data
ARMI 2012 Annual Update
Authors: Hossack B, Adams M, Waddle H, Grant E, Fisher R, Battaglin W, Ball L | Format: .PDF
Welcome to the 2012 ARMI Annual Update, which 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 more than 420 peer-reviewed publications since its inception. Some of those publications are highlighted in this fact sheet. Please visit our website (http://armi.usgs.gov) for additional information on ARMI products, to find summaries of research topics, to search for ARMI activities in your area, or to obtain amphibian photographs. This year, we introduced a new feature on the ARMI website called “Trend Data” that provides occupancy and abundance estimates at the project level (armi.usgs.gov/projects/estimates_datasets.php)
. Data can be accessed in tabular format or plotted via an interactive map.
Full text: armi.usgs.gov/docs/ARMI%202012%20Annual%20Update.pdf
ARMI 2011 Annual Update
Authors: Adams M, Muths E, Grant E, Miller DA, Waddle H, Walls S, Ball L | Format: .PDF
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: armi.usgs.gov/docs/ARMI%202011%20Annual%20Update.pdf
Amphibians in the climate vice: loss and restoration of relilience of montane wetland ecosystems of the American West
Authors: Ryan ME, Palen WJ, Adams MJ, Rochefort RM | Date: 2014-05-01 | Outlet: Frontiers in Ecology and the Environment 12:232-240
Wetlands in the remote mountains of the American West are the site of two massive ecological “experiments” spanning the 20th Century. In a kind of biological carpet-bombing following World War II, fish and wildlife managers introduced millions of predatory trout into fishless mountain ponds and lakes across the Western United States. The new top predators, which now occupy 95% of large mountain lakes, have truncated the habitat distributions of native frogs, salamanders, and wetland invertebrates to smaller, more ephemeral ponds where fish do not survive. Now a second “experiment” –anthropogenic climate change – threatens to push from the opposite direction; eliminating many ephemeral habitats and shortening wetland hydroperiods. Caught between climate-induced habitat loss and predation from introduced fish, native mountain lake fauna of the American West – especially amphibians– are at risk of being squeezed out. Targeted fish removals, guided by models of wetlands change, provide new strategies for restoring resilience.
Assessing the terrestrial movement patterns and habitat preferences of the common toad (Bufo bufo) in a montane area of Central Spain
Authors: D Daversa, E Muths, J Bosch | Date: 2012 | Outlet: Journal of Herpetology | Format: .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.