Studying amphibian declining numbers

They may have outlived dinosaurs, but amphibians increasingly struggle for survival in the 21st century.
More than 30 percent of species are listed as threatened or endangered. While scientists work to pinpoint causes for the decline, some suggest that amphibians — like canaries in a mine shaft — sound an ominous early warning for the rest of us.
Among those monitoring amphibians worldwide are WSU researchers Paul Verrell and Peter Ritson. Verrell, associate professor in the School of Biological Sciences, said concern about amphibian decline initially surfaced in 1989.
(Paul Verrell with some of the frogs, lizards and turtles in his office. Photo by Becky Phillips, WSU Today.)  
 It soon became apparent that amphibians were not only disappearing in cities and agricultural areas, but also on mountain tops and other pristine areas apparently unaffected by human habitation.
In response, the International Union for Conservation of Nature (IUCN) Global Amphibian Assessment (GAA) was launched — with the goal of collecting data on all described species of amphibians. The IUCN regularly publishes a “red list” that shows the level of threat to each species.
Surveying populations
“Of the 5,915 identified (amphibian) species in 2007, 1,800 of them were judged to be threatened,” said Verrell.
(Peter Ritson, WSU Vancouver, and one of his interns on the amphibian census project. Photos by Steph Earnest, WSU Vancouver.)
“Fifty-three of those species are native to the United States. And only one species found in western parts of Washington state is a candidate for future listing — the Oregon Spotted Frog.”
Ritson, instructor of environmental science at WSU Vancouver, has a personal interest in those frogs. He is conducting a census of the amphibian population in Clark County — one of the fastest growing counties in the state. His primary focus is on loss of habitat in the area.
Sponsored by the Washington Department of Fish and Wildlife, Ritson hopes to establish a regional database for the five remaining native pond-breeding species.
Volunteers, whom he trained to identify amphibian egg masses, are surveying wetland habitats to determine
numbers of the western toad, northern red-legged frog, northwestern salamander, long-toed salamander and Pacific chorus frog.
“Higher emphasis is being placed on the western toad due to its unexplained declines and disappearances from lowland areas,” said Ritson. See more at
Information collected ultimately will help guide management decisions including future land-use strategies. According to Verrell’s research, those strategies should include more judicious use of herbicides and pesticides in wetland settings — including residential ponds.
He says that amphibians, with their permeable skins, are highly sensitive to changes in both terrestrial and aquatic environments and thereby act as valuable indicator species for threats to other animals.
Verrell has shown that even minute concentrations of herbicides such as Roundup ™ and atrazine can be toxic to larval frogs and salamanders, directly or indirectly leading to death. He concedes that “although we can test precisely in a lab, predicting risk in a (natural) environment is really very difficult.”
Global warming a factor
Yet environmental contamination is only one cause for amphibian decline. There is a long list of synergistic culprits ranging from habitat destruction, hunting and introduction of alien species to higher levels of UV radiation, diseases and more.
One current theory suggests that large-scale global warming has led to changes favoring the growth of a fungal disease called chytrid (Batrachochytrium dendrobatidis) — implicated in widespread death of amphibians.
“We have good evidence of amphibian decline and growing evidence for the causes,” said Verrell. “Now we need to act to reverse or at least halt this decline.”
Organizations such as the Amphibian Ark and GAA are hoping to do just that. Captive breeding and reintroduction programs are just some of the ways biologists are working to save the more than 6,000 amphibian species from extinction.
Leaping lizards!
There really are leaping lizards … and flying  snakes and frogs. But you won’t find them sailing around the wheat fields of eastern Washington or anywhere else in the U.S. Instead, they dwell high in the trees of dense southeast Asian tropical jungles.
According to Paul Verrell, associate professor in the School of Biological Sciences, the draco lizard “flies” with very long ribs that extend beyond the boundary of the body.
The ribs are draped with membranes that spread open like wings as the reptile leaps from tree to tree. Wallace’s flying frog also uses the same type of “parachute technology” — webbing between the toes and skin flaps along the sides. The frogs can sail up to 50 feet or more, their landing cushioned by large, spongy toe pads.
Flying snakes, which can grow up to 4 feet in length, are actually gliders. The most sophisticated of the lot, Verrell explained that these creatures propel themselves from trees and then flatten their bodies (top to bottom) into a concave shape that traps air.
As they undulate back and forth, they can actually turn and maneuver to a greater extent than even mammalian flying squirrels. Flying snakes can travel up to 330 feet in the air as they strive to avoid predators or search for prey.
For photos and more information, visit
For more information on Verrell’s research visit

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