Evaluating breeding and metamorph occupancy and vernal pool management effects for wood frogs using a hierarchical model

Authors

  • Adam W. Green,

    Corresponding author
    • Department of Fish, Wildlife and Conservation Biology, Colorado State University, Fort Collins, CO, USA
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  • Mevin B. Hooten,

    1. Department of Fish, Wildlife and Conservation Biology, Colorado State University, Fort Collins, CO, USA
    2. US Geological Survey, Colorado Cooperative Fish and Wildlife Research Unit, 1484 Campus Delivery, Colorado State University, Fort Collins, CO, USA
    3. Department of Statistics, Colorado State University, Fort Collins, CO, USA
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  • Evan H. Campbell Grant,

    1. US Geological Survey, Patuxent Wildlife Research Center, S.O. Conte Anadromous Fish Laboratory, Turners Falls, MA, USA
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  • Larissa L. Bailey

    1. Department of Fish, Wildlife and Conservation Biology, Colorado State University, Fort Collins, CO, USA
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Correspondence author. E-mail: awgreen@colostate.edu

Summary

  1. World-wide declines in amphibian populations are often attributed to loss of habitat and exploitation; additionally, climate change may play an important role in future declines. Despite protection of habitat, amphibians relying on temporary habitats, such as vernal pools, may need active management to maintain their populations under forecasts of warming temperatures and more variable precipitation. However, few studies have examined the factors influencing where these species choose to breed (breeding occurrence) and the conditional likelihood of successful metamorphosis, while accounting for imperfect detection.

  2. We developed an occupancy model and estimated parameters within a Bayesian framework to investigate the factors influencing probabilities of wood frog Lithobates sylvatica breeding and successful metamorphosis at Patuxent Research Refuge, Maryland, USA. Our objectives were to obtain estimates of breeding occurrence and metamorph occupancy and evaluate the success of current management actions.

  3. The probabilities of wood frog breeding and successful metamorphosis varied by year and were positively related to the pond's typical hydroperiod length and annual precipitation. Contrary to our predictions, previous occupancy states had little effect on breeding and metamorph occupancy probabilities, which is likely to be due to high correlation of occupancy with hydroperiod length. Additionally, we did not observe a relationship between breeding occupancy probabilities and the spatial arrangement of pools. Although sample sizes were small, management actions resulted in an increase in both breeding and metamorph occupancy probabilities.

  4. Synthesis and applications. We demonstrate that management actions targeting short-hydroperiod pools favourably influence both components of breeding success. However, continued monitoring is needed to determine whether managed pools remain suitable for wood frogs. With predicted changes in climate and a positive relationship between breeding occupancy and winter precipitation, a proactive focus on active management of vernal pools may provide a means to maintain wood frog populations in the future.

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