Date: 6/24/08
Contact: C. Doug Nielsen
Phone: (702) 486-5127, ext. 3500

AMPHIBIANS IN THE DESERT

In case you missed it, 2008 is a leap year – the perfect criterion for making it the “Year of the Frog.” And that’s just what wildlife conservationists from around the world have done in creating a coordinated public awareness campaign to inform people around the globe about the plight of amphibians.

Populations of frogs, toads, newts and salamanders are declining worldwide. Estimates are that one third of all amphibians worldwide, and two-thirds of those in the United States, are considered to be in trouble. Ten percent of the U.S. species are severely at risk. The majority of the problems creating this situation are anthropogenic, or human-caused. Habitat loss is one of the top factors, and relates to the draining and alteration of wetlands. Other factors include pesticide use and the spread of invasive species, as well as the non-human factors of climate fluctuation and disease. Recently, a disease known as Bd, or chytrid fungus, has been found to be causing large casualties in amphibian populations.

Amphibians are especially vulnerable to changes in their environment because their skin is highly permeable. This adaptation allows them to regulate fluids into and out of their bodies, but also it allows for the easy entry of contaminants. So as the environment changes, biologists first see the effects in amphibians.

The same is true for life in the Nevada desert. Frogs are not the type of animal you would expect to see in a desert environment, but they’re here, along with a number of toads. How do you tell the difference between frogs and toads? The Audubon Society makes it easy with these descriptions: Frogs are water dwellers with long legs and slimy skin, and toads are short, squat, land dwellers with dry, warty skin.

Some of the frogs and toads that can be seen in Southern Nevada include the Pacific Tree frog or Chorus Frog, Great Basin Spadefoot toad, Woodhouse’s toad, Relict Leopard frog, Amargosa toad, Columbia Spotted frog, Southwestern toad, Red-spotted toad and the Great Plains toad. Those who would like to know what these critters look like will find an identification guide on the Nevada Department of Wildlife website at www.ndow.org/wild/animals/facts/nvfrogs_toads.pdf.

Brian Hobbs, a native fish and amphibian biologist for NDOW, recently completed surveys for Amargosa toads near the town of Beatty about 120 miles north of Las Vegas. This toad only occurs in the Oasis Valley along a 10-mile stretch of the Amargosa River and some adjacent upland springs. Hobbs was joined by other biologists and even a few volunteers. While Hobbs and company had trouble with the toads not coming out on cool and windy nights, their counts were successful nonetheless. Hobbs said, the population is holding steady, even doing slightly better than it was ten years ago.

The protected toad, like every other living thing in the desert, “would benefit from some more rain,” he said. Hobbs and other biologists are hoping that the Amargosa toad won’t end up like the now extinct Vegas Valley leopard frog. Loss of spring related habitat to ongoing construction in the valley played a significant role in that frog’s extinction. Biologists also believe that the American bullfrog squeezed the leopard frog out. The non-native bullfrog has loudly announced its presence here since it was introduced into the Las Vegas valley sometime in the last century, invading wetlands and preying upon native species.

The relict leopard frog still persists in the area, but its range has diminished. Once common from southwestern Utah to below the Hoover Dam, the relict leopard frog now exists only at five geothermal spring wetlands and is a protected species.

If frogs, toads and other amphibians continue to decline in Nevada and worldwide, it will affect the delicate ecology of the wetland areas where they live. These animals are in the middle of the food web, which means that they consume a large number of invertebrates, as well as being a food source for snakes, birds, and other animals. Interestingly, tadpoles consume algae and sediment, which can affect water quality.

“There is no one thing causing declines in amphibians and usually there are several things acting at the same time on the same population,” Hobbs said. “It is also important to note that amphibians are very resilient and populations can recover once the threats are removed or at least ameliorated to some extent.”

The Nevada Department of Wildlife (NDOW) protects, restores and manages fish and wildlife, and promotes fishing, hunting, and boating safety. NDOW's wildlife and habitat conservation efforts are primarily funded by sportsmen's license and conservation fees and a federal surcharge on hunting and fishing gear. Support wildlife and habitat conservation in Nevada by purchasing a hunting, fishing, or combination license. For more information, visit www.ndow.org.