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Water Quality
Amphibian Study
Little is known about anuran (i.e., frog and toad) species diversity in the Wash. We do know that a variety of anurans are found in wet areas throughout Clark County including the bullfrog (Rana catesbeiana), Woodhouse’s toad (Bufo woodhousii), Arizona toad (B. microscaphus), red-spotted toad (B. punctatus), relict leopard frog (R. onca), pacific treefrog (Hyla regilla), and spadefoot toads (Scaphiopus sp.). Species like the relict leopard frog have only recently been “rediscovered” in Clark County, and there is considerable interest in this animal because it has been proposed for listing under the Endangered Species Act.
The last known studies of anurans in the Wash were conducted in the 1970s. The purpose of this study was to investigate the current diversity of anurans along the Wash using a visual encounter survey methodology. This baseline inventory will help fill a 30-year gap in monitoring and study of anuran species diversity in the Wash. After the baseline data has been analyzed, we will have the tools we need to make decisions that incorporate specific management actions, which could reduce threats to these species and to propose site-specific conservation actions if needed.
The amphibian study was implemented in April 2004 and completed in October 2005. Visual encounter surveys (VES) were used to determine the presence of amphibians in the Wash. Studies such as these have been used in this region to survey for amphibian populations. These surveys were conducted at night when adult anurans are more easily detected. Surveys consisted of visual and audio searches of aquatic habitats close to shorelines and terrestrial habitat within several meters of water. These surveys were generally conducted by two individuals using both headlamps and high intensity flood-lights.
Audio searches for calling individuals were used to identify breeding sites. Surveys were conducted approximately three to five nights of each month. This allowed the potential for detection of early breeding anurans, such as the pacific treefrog, and other species that may not breed until the summer monsoons, such as spadefoot toads.
Visual encounter surveys revealed the presence of two anurans using the Wash. They are the bullfrog and the Woodhouse’s toad.
Additional Information: Distributional changes and population status of amphibians in the Eastern Mojave Desert
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