The Center for Biological Diversity and Southern Utah Wilderness Alliance petitioned the U. S. Fish and Wildlife Service in May 2002 to list a rare southwestern amphibian, the relict leopard frog, as an endangered species under the Endangered Species Act. The Fish and Wildlife Service designated the relict leopard frog as a “Candidate” species for federal listing in July 2002, and is currently drafting a Conservation Agreement and Strategy with state and federal wildlife agencies. The Center filed a lawsuit in 2005 against the Service for failing to make “expeditious progress” in protecting the relict leopard frog and 285 other known imperiled species on the candidate waiting list.

The relict leopard frog was one of the first North American amphibians thought to have become extinct. The last historical collections of the species were in the 1950s and a handful of relict leopard frog populations were only rediscovered in the early 1990s. This extremely endangered amphibian is now restricted to six springs in two separate localities within the Lake Mead National Recreation Area in Nevada. It is estimated that less than 1,100 adult relict leopard frogs remain, putting the species at severe risk of extinction.

The species historically occurred in springs, seeps, and wetlands within the Virgin, Muddy, and Colorado River drainages, in Utah, Nevada, and Arizona. Populations of the extinct “Vegas Valley leopard frog,” which once inhabited springs in the Las Vegas, Nevada area, were considered by many herpetologists to be the same species as the relict leopard frog. The species has been extirpated from 91% of its known historical localities. Since relict leopard frogs were rediscovered in eight springs in the 1990s near Lake Mead and along the Virgin River, frogs have disappeared from two of these sites in the last decade. The species has been extirpated from Utah, Arizona, and from the Muddy River drainage in Nevada, and persists in only a tiny fraction of its known historical range.

Habitat changes due to water development, and agricultural and urban development impacts were responsible for eliminating much of the frog’s original habitat. The damming of the Colorado River and the formation of Lake Mead Lake in 1935, and Lake Mojave in 1951 flooded relict leopard frog habitat, reduced connectivity between the remaining populations, and altered the hydrologic regime necessary to maintain relict leopard frog habitats.

Ross Haley, National Park Service
Ross Haley, National Park Service

The remaining relict leopard frog populations suffer from low genetic variation and are very vulnerable to extinction due to population fragmentation and the small size and isolation of their remaining habitat. The species is also threatened by potential water development along the Muddy and Virgin Rivers; predation and competition by introduced species such as bullfrogs, exotic fish, and crayfish; habitat alteration by invasive plants; the potential for contracting diseases that have hit other leopard frog species in the region; impacts from feral burros; recreational impacts by visitors to Lake Mead; and habitat alteration due to natural erosion and scouring.

graphic Andrew Rodman ©2002
February 9, 2006
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