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

Abstract/Summary

1. Worldwide 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 seasonal 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.<br />
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.<br />
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 due to high correlation of occupancy with hydroperiod. Though sample sizes were small, management actions resulted in an increase in both breeding and metamorph occupancy probabilities.<br />
4. Synthesis and applications. We demonstrate that management actions targeting short-hydroperiod pools favorably influence both components of breeding success. Still, continued monitoring is needed to determine whether managed pools remain suitable for wood frogs. With predicted changes in climate and a positive relationship between <br />
breeding occupancy and winter precipitation, a proactive focus on active management of vernal pools may provide a means to maintain wood frog populations into the future.

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