Effects of Weather on Survival in Populations of Boreal Toads in Colorado

Scherer, Rick D.; Muths, Erin; Lambert, Brad A.

doi:10.1670/07-257.1

Cited by 26 publications

(26 citation statements)

References 2 publications

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“…As predicted, survival rates were higher in the Bd ‐negative (77%, DC), compared to the Bd ‐positive (52%, BR), population. Previous work shows similar survival rates for male and female boreal toads (Scherer, Muths & Lambert 2008; Muths, Scherer & Lambert 2010), such that results from this study (male data only) may be applicable to other boreal toad populations.…”

Section: Discussionsupporting

confidence: 73%

Compensatory effects of recruitment and survival when amphibian populations are perturbed by disease

Muths

Scherer

Pilliod

2011

Journal of Applied Ecology

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107

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Summary1. The need to increase our understanding of factors that regulate animal population dynamics has been catalysed by recent, observed declines in wildlife populations worldwide. Reliable estimates of demographic parameters are critical for addressing basic and applied ecological questions and understanding the response of parameters to perturbations (e.g. disease, habitat loss, climate change). However, to fully assess the impact of perturbation on population dynamics, all parameters contributing to the response of the target population must be estimated. 2. We applied the reverse-time model of Pradel in Program mark to 6 years of capture-recapture data from two populations of Anaxyrus boreas (boreal toad) populations, one with disease and one without. We then assessed a priori hypotheses about differences in survival and recruitment relative to local environmental conditions and the presence of disease. 3. We further explored the relative contribution of survival probability and recruitment rate to population growth and investigated how shifts in these parameters can alter population dynamics when a population is perturbed. 4. High recruitment rates (0AE41) are probably compensating for low survival probability (range 0AE51-0AE54) in the population challenged by an emerging pathogen, resulting in a relatively slow rate of decline. In contrast, the population with no evidence of disease had high survival probability (range 0AE75-0AE78) but lower recruitment rates (0AE25). 5. Synthesis and applications. We suggest that the relationship between survival and recruitment may be compensatory, providing evidence that populations challenged with disease are not necessarily doomed to extinction. A better understanding of these interactions may help to explain, and be used to predict, population regulation and persistence for wildlife threatened with disease. Further, reliable estimates of population parameters such as recruitment and survival can guide the formulation and implementation of conservation actions such as repatriations or habitat management aimed to improve recruitment.

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Section: Discussionsupporting

confidence: 73%

Compensatory effects of recruitment and survival when amphibian populations are perturbed by disease

Muths

Scherer

Pilliod

2011

Journal of Applied Ecology

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107

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“…6 and 34, but see ref. 35), these results suggest that under certain circumstances, a warming climate may be helpful to some amphibian populations, particularly those that live in harsh conditions at the edge of their thermal tolerances. A reduced winter severity could benefit high and low elevation populations of R. luteiventris alike, although failures in recruitment due to drying of breeding habitat may overwhelm positive effects of warmer winters in some populations, especially at lower elevations and latitudes.…”

Section: Discussionmentioning

confidence: 85%

Decreased winter severity increases viability of a montane frog population

McCaffery

Maxell

2010

Proc. Natl. Acad. Sci. U.S.A.

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Many proximate causes of global amphibian declines have been well documented, but the role that climate change has played and will play in this crisis remains ambiguous for many species. Breeding phenology and disease outbreaks have been associated with warming temperatures, but, to date, few studies have evaluated effects of climate change on individual vital rates and subsequent population dynamics of amphibians. We evaluated relationships among local climate variables, annual survival and fecundity, and population growth rates from a 9-year demographic study of Columbia spotted frogs (Rana luteiventris) in the Bitterroot Mountains of Montana. We documented an increase in survival and breeding probability as severity of winter decreased. Therefore, a warming climate with less severe winters is likely to promote population viability in this montane frog population. More generally, amphibians and other ectotherms inhabiting alpine or boreal habitats at or near their thermal ecological limits may benefit from the milder winters provided by a warming climate as long as suitable habitats remain intact. A more thorough understanding of how climate change is expected to benefit or harm amphibian populations at different latitudes and elevations is essential for determining the best strategies to conserve viable populations and allow for gene flow and shifts in geographic range.amphibian | climate change | demography | Rana luteiventris | snowpack A mphibian populations are declining around the globe at an alarming rate (1-3), and climate change now figures prominently as a potential interactive driver of some of these declines (4-6). A shift to earlier breeding phenology has been documented in a number of species (7-11), but this shift is not universal across species and has not been tied to population-level consequences. Other work has associated climatic conditions with disease-related declines in the Neotropics (4, 5), yet no mechanisms have been definitively linked to these correlations (12, 13). Reading et al. (14) showed a decrease in adult female body condition and survival in a population of common toads (Bufo bufo) that corresponded with an increase in average annual temperatures. However, these demographic changes were not explicitly linked to changes in population size over time. Kiesecker et al. (15) showed that disease, UV-B, and climate change could interact to increase embryo mortality in western toad (Bufo boreas) populations, yet these populations have not declined. This increased premetamorphic mortality may not be sufficient to cause otherwise increasing populations to decline in the long term. Alternatively, it may be that conditions in short-term or laboratory-based studies are not always representative of long-term patterns in natural populations. To determine mechanisms of population change, we first need to know which vital rates are affected by changes in climate, and then how these changes affect population dynamics.The effects of climate change on growth and survival are particularly relev...

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“…We visited 3 breeding sites in the Middle Cottonwood Creek drainage and South Cottonwood Creek drainage in the southern Rocky Mountains, Colorado, USA (Fig. ; Scherer et al ) from 1999 to 2013. The study area was situated within dense subalpine forest dominated by Engelmann spruce ( Picea engelmannii ), Rocky Mountain subalpine fir ( Abies bifolia ), and quaking aspen ( Populus tremuloides ) with an understory of willow ( Salix sp.)…”

Section: Study Areamentioning

confidence: 99%

Influence of demography and environment on persistence in toad populations

et al. 2016

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Effective conservation of rare species requires an understanding of how potential threats affect population dynamics. Unfortunately, information about population demographics prior to threats (i.e., baseline data) is lacking for many species. Perturbations, caused by climate change, disease, or other stressors can lead to population declines and heightened conservation concerns. Boreal toads (Anaxyrus boreas boreas) have undergone rangewide declines due mostly to the amphibian chytrid fungus Batrachochytrium dendrobatidis (Bd), with only a few sizable populations remaining in the southern Rocky Mountains, USA, that are disease‐free. Despite the apparent region‐wide occurrence of Bd, our focal populations in central Colorado were disease free over a 14‐year capture‐mark‐recapture study until the recent discovery of Bd at one of the sites. We used recapture data and the Pradel reverse‐time model to assess the influence of environmental and site‐specific conditions on survival and recruitment. We then forecast changes in the toad populations with 2 growth models; one using an average lambda value to initiate the projection, and one using the most recent value to capture potential effects of the incursion of disease into the system. Adult survival was consistently high at the 3 sites, whereas recruitment was more variable and markedly low at 1 site. We found that active season moisture, active season length, and breeding shallows were important factors in estimating recruitment. Population growth models indicated a slight increase at 1 site but decreasing trends at the 2 other sites, possibly influenced by low recruitment. Insight into declining species management can be gained from information on survival and recruitment and how site‐specific environmental factors influence these demographic parameters. Our data are particularly useful because they provide baseline data on demographics in populations before a disease outbreak and enhance our ability to detect changes in population parameters potentially caused by the disease. © 2016 The Wildlife Society.

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Effects of Weather on Survival in Populations of Boreal Toads in Colorado

Cited by 26 publications

References 2 publications

Compensatory effects of recruitment and survival when amphibian populations are perturbed by disease

Compensatory effects of recruitment and survival when amphibian populations are perturbed by disease

Decreased winter severity increases viability of a montane frog population

Influence of demography and environment on persistence in toad populations

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