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Conserving Columbia spotted frogs in Nevada.

Columbia spotted frogs (Rana luteiventris) in the Great Basin of Nevada have been a candidate for Endangered Species Act protection since 1993. Most populations in this region are small and highly fragmented, and are highly vulnerable to changes in their environment. Development of water sources, poor grazing practices, certain mining activities, and the introduction of non-native species have contributed to habitat degradation and fragmentation. Emerging fungal diseases such as chytridiomycosis and the spread of parasites also threaten some populations, as do the effects of climate change (such as drought) and random events like wildfires. The potential for listing the Columbia spotted frog as a threatened or endangered species prompted an array of interests to develop a multi-party conservation agreement and strategy in order to make listing unnecessary.

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Columbia spotted frogs are found at scattered locations from southeast Alaska down through British Columbia, eastern Washington and Oregon, as well as in northern Idaho, Montana, Wyoming, Utah, and Nevada. In Nevada, populations occur in three distinct areas: the Toiyabe Mountain Range in Nye County (Toiyabe subpopulation), the Ruby Mountain and Jarbidge-Independence Ranges in Elko County (Northeast subpopulation), and the Deep Creek drainage in White Pine County, Nevada, and Toole County, Utah (West Desert population). The West Desert population is managed by the Utah Division of Wildlife Resources and the U.S. Fish and Wildlife Service's Utah Fish and Wildlife Office.

Columbia spotted frogs are closely associated with clear, slow-moving or ponded surface waters with little shade and relatively constant water temperatures. Reproducing populations occur in habitats characterized by springs, floating vegetation, and larger bodies of pooled water (e.g., oxbows, lakes, stock ponds, beaver-created ponds, seeps in wet meadows, backwaters). In colder portions of their range, Columbia spotted frogs will use areas where water does not freeze, such as spring heads and undercut streambanks with overhanging vegetation. Females usually lay egg masses in the warmest areas of a pond, typically in shallow water, and clutch sizes vary in size from 150 to 2,400 eggs. Successful egg production and metamorphosis into adult frogs are susceptible to habitat variables such as temperature, depth and pH of water, the amount of cover, and the presence of predators.

Adult Columbia spotted frogs measure 2 to 3 inches (5 to 8 centimeters) from snout to vent, with females being larger than males. They are light brown, dark brown, or gray dorsally, with small spots. Ventral coloration can differ among populations and may range from yellow to salmon; however, very young individuals may have very pale, almost white ventral surfaces. The head may have a dark mask with a light stripe on the upper jaw, and the eyes are turned slightly upward. Male frogs have swollen thumbs with darkened bases.

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Conservation Agreement and Strategy

A 10-year Conservation Agreement and Strategy (CAS) was signed in September 2003 for both the Northeast and the Toiyabe subpopulations of the Columbia spotted frog in Nevada. Signatories included the Bureau of Land Management, Nevada Department of Wildlife, Nevada Natural Heritage Program, Nye County, U.S. Fish and Wildlife Service, U.S. Forest Service, and the University of Nevada--Cooperative Extension. The partners agreed to conduct inventories to establish distribution and abundance, assess threats, maintain legal protection for the frog, implement conservation actions identified in the agreement, conduct research to support conservation of the species, and increase public awareness of, and appreciation for, the Columbia spotted frog.

The conservation agreements and strategies identify actions that federal, state, and local agencies will take to reduce threats, improve degraded habitat, and restore natural functions associated with riparian systems. While directly improving frog habitat, these actions will also benefit other aquatic species and improve natural hydrological functions.

By the end of 2007, 8 percent of the tasks listed in the Northeast CAS were completed and an additional 74 percent of the tasks had been initiated at some level. Additionally, 22 percent of the identified tasks listed in the Toiyabe Mountains CAS were completed and an additional 68 percent of the tasks had been initiated at some level. For example, the availability of adequate habitat was identified as a limiting factor for the Toiyabe Mountains subpopulation. In response, a habitat enhancement project completed in the fall of 2004 included the construction or improvement of 22 ponds in Indian Valley Creek. A variety of designs were used to create breeding, rearing, and over-wintering habitat. Biologists are monitoring the effectiveness of this habitat enhancement project.

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Since the CASs were signed, annual egg mass surveys have been conducted and mark-recapture surveys have been performed during the summer. These surveys are a collaborative effort of all signatories to the agreements. Data gathered during the annual surveys will be used to track population trends, assess threats, determine the effectiveness of habitat restoration projects, and provide information on survival, growth, and movement of Columbia spotted frogs in the Great Basin. If the agreements are successful, it may become unnecessary to list these frogs as threatened or endangered.

Chad Mellison(chad_mellison@fws. gov; 775-861-6300) is a fish and wildlife biologist in the Service's Nevada Fish and Wildlife Office in Rena
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Author:Mellison, Chad
Publication:Endangered Species Update
Date:Jan 1, 2008
Words:852
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