Forecasting population responses to natural and anthropogenic stressors is a fundamental challenge for ecologists, conservation biologists, and wildlife managers. Predicting amphibian population trajectories, in particular, poses an additional challenge because different life-stages (e.g. aquatic larva, terrestrial adults) rely on highly disparate resources, making it difficult to predict the life-stage(s) at which the effects of stressors may manifest. Furthermore, many amphibians breed, forage, and hibernate in spatially disparate habitats. Changes to or degradation of any of these environments or migratory pathways between them may therefore negatively influence one or several life-stages. Effective management of amphibian populations therefore requires considering individual and population responses to natural and anthropogenic pressures (e.g. timber harvest, livestock grazing) across multiple life-stages and a variety of habitats. Yet, assessments of multiple stressors across amphibian life-stages have been largely theoretical or laboratory based, and empirical evidence from natural populations is still lacking.
Field assessments of multiple stressors on amphibian populations are critical and timely, particularly given current trends in species declines. In recent decades, global amphibian populations have been declining at alarming rates, and many species have gone extinct. Human-induced habitat change has been cited as a dominate cause, which can interact with other stressors such as climate warming and disease. In the majority of cases, however, mechanisms underlying declines are considered enigmatic. Developing a better understanding of the individual and interactive factors threating amphibians will therefore be critical to preclude further population declines and species extinctions.
This research investigates the influence of natural and anthropogenic stressors on multiple amphibian life-stages through assessing how habitat disturbance from livestock grazing may interact with disease and climatic variables to influence the behavior and demographics of a declining anuran species, the boreal toad (Anaxyrus boreas boreas). Our overarching research question is: How do disease, livestock grazing, and annual weather patterns influence the behavior, ecology, and demographics of boreal toads across multiple life-stages? We address this question by assessing relevant parameters at the individual level (movement, habitat selection) and the population level (survival, recruitment) using diverse field methods (radio-telemetry, counts, capture-mark-recapture) and analytical tools (resource selection functions, state-space models, survival analysis). Our specific research objectives are to:
- Evaluate adult boreal toad movement and habitat selection in relation to disease and livestock grazing.
- Estimate adult boreal toad annual survival and recruitment in relation to disease, livestock grazing regimes, habitat characteristics, and weather variables.
- Characterize the placement of egg clutches, and estimate tadpole and metamorph survival for boreal toads in relation to disease, predation, livestock grazing, and habitat conditions.
Assessing behavioral responses, quantifying population dynamics, and identifying the life-stage(s) at which the effects of specific stressors manifest will help target management actions and provide valuable information to the several agencies working to improve conservation of boreal toad populations in Wyoming. More broadly, our comprehensive approach to understanding responses of wildlife to various environmental stressors may provide a framework for future studies in diverse systems.
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Gabe Barrile, PhD Student
Wyoming Cooperative Fish and Wildlife Research Unit
Department of Zoology and Physiology
Program in Ecology, University of Wyoming
Dept. 3166, 1000 E. University Avenue
Laramie, WY 82070
Gabe graduated from Bloomsburg University, PA in 2013, majoring in Biology. His undergraduate research focused on life-history trait evolution in Fowler’s toads (Anaxyrus fowleri ) on several Atlantic Coast barrier islands. Additionally, Gabe compared time-budgeting behavior between captive and free-ranging black-handed spider monkeys (Ateles geoffroyi ) on the Osa Peninsula of Costa Rica. After graduation, he taught coastal and marine ecology at the Chincoteague Bay Field Station near Wallops Island, VA.
Funding & Partners
Wyoming Game and Fish Department (Primary)
United States Forest Service
Laramie Audubon Society
Western Ecosystems Technology, Inc.