Demography and habitat use of boreal toads (Anaxyrus boreas) and other amphibians in northern Wyoming (Blackrock).

Amphibian decline is a problem of global importance, with over 40% of species considered at risk. This phenomenon is not limited to the tropics or to other countries. Amphibian species in the U.S. are also declining, contributing to the larger, global phenomenon. For example, in the State of Wyoming, the Wyoming toad has been extirpated in the wild and the boreal toad is a species of special concern. Understanding biotic and abiotic factors that influence amphibian persistence is critical for amphibian conservation. This work in northern Wyoming has focused on demography, habitat alteration and creation, and disease in the context of multiple amphibian populations. One of the foci has been to identify the capacity for mitigation wetlands (those created to offset losses due to, for example, road construction) to serve as habitat for amphibians. Four species of amphibians native to Wyoming, including the boreal toad, reside in this region. Our previous research indicates that the toad population at Blackrock is declining at 5-6% per year and that disease due to the amphibian chytrid fungus is contributing to this decline. Our demographic work at this site began in 2003, focusing solely on the boreal toad. Additional funding in 2012 allowed us to increase the scope of the project and assess chorus frog, salamander and Columbia spotted frog populations, invertebrate assemblages, work to quantify the use of mitigation sites by amphibians, and to expand efforts to include sites on Togwotee Pass a short distance away from Blackrock. Because most previous studies of amphibian use of created wetlands have taken place in the eastern United States, this project, incorporating demographic and disease dynamics as well as community composition and mitigation effects of created wetlands, is unique and provides a case study in the Intermountain West. By 2015, all four native amphibian species were observed at one of the created wetlands, and all of them, including the boreal toad, were breeding (evidenced by breeding behavior, eggs or tadpoles).

两栖动物种群衰退是具有全球重要性的环境议题，目前全球超40%的两栖动物物种被列为受威胁物种。这一现象并非仅局限于热带地区或特定国家，美国境内的两栖动物种群同样面临衰退，这亦是全球两栖动物衰退现象的重要组成部分。以怀俄明州为例，怀俄明蟾蜍（Wyoming toad）已在野外彻底灭绝，而北方蟾蜍（boreal toad）则被列为特殊关注物种。阐明影响两栖动物存续的生物与非生物因子，对于两栖动物保护工作至关重要。本研究以怀俄明州北部的多种群两栖动物为对象，围绕种群动态、栖息地改造与营造及疫病相关问题三个核心方向展开，其中一项关键研究目标为评估补偿湿地——即用于抵消道路建设等人类活动导致的栖息地丧失而人工营造的湿地——作为两栖动物栖息地的可行性。该区域分布有怀俄明州本土的4种两栖动物，其中便包括北方蟾蜍（boreal toad）。我们此前的研究显示，布莱克罗克（Blackrock）区域的北方蟾蜍种群正以每年5%-6%的速率衰退，而两栖动物壶菌（amphibian chytrid fungus）引发的疫病正是该衰退的重要诱因之一。本研究在该区域的种群动态监测工作始于2003年，最初仅针对北方蟾蜍开展。2012年新增的项目资金使得我们得以拓展研究范围：新增对鸣蟾（chorus frog）、蝾螈（salamander）及哥伦比亚斑点蛙（Columbia spotted frog）的种群调查，同时开展无脊椎动物群落组成研究、量化两栖动物对补偿湿地的利用情况，并将研究区域扩展至距离布莱克罗克不远的托格蒂山口（Togwotee Pass）。由于此前绝大多数关于两栖动物利用人工营造湿地的研究均集中于美国东部地区，本研究同时涵盖种群动态、疫病动态、群落组成及人工营造湿地的补偿效应，因此具有独特性，可为美国西部山间区域提供优质的研究案例。截至2015年，研究人员在其中一处人工营造湿地中观测到全部4种本土两栖动物，且包括北方蟾蜍在内的所有物种均出现繁殖行为（可通过繁殖活动、卵群或蝌蚪个体予以证实）。