Tales from the Froglog and others.

Tales from the Froglog and others

What's a Froglog? David B. Wake, a biologist at the University of California, Berkeley, and conference chairman, gathered information from around the world on amphibian declines in a digest given that whimsical title. Highlights from the Froglog and meeting include:

Canada: Richard Wassersug of Dalhousie University in Halifax, Nova Scotia, who has studied frogs in that province for eight years, says several species are on the wane or have not been sighted recently, including leopard frogs and an albino form of the North American species Rana clamitans.

Japan: Masafumi Matsui of Kyoto University notes that several species have declined, but attributes most losses to direct environmental change -- notably the conversion of rice paddies to housing and golf courses.

Norway: Since 1966, biologists have documented losses of the common European toad, Bufo bufo, on islands in the outer regions of Oslo's fjord.

Puerto Rico: Since the mid- to late 1970s, three species of miniature frogs -- Eleutherodactylus japseri, E. karlschmidti and E. enidae -- have apparently disappeared, and one species, E. unicolor, has become rare. In addition, the once common E. coqui, E. richmondi and E. wightmanae have experienced dramatic declines in the last three years, says Margaret Stewart of the State University of New York at Albany.

Southeastern United States: This region shows little evidence of a general population decrease except for areas with obvious habitat destruction. Researchers note several declines, including the population of the large, stream-dwelling salamander Cryptobranchus; the chorus frog, Pseudacris triseriata, is either rare or has vanished in southern coastal areas where it once thrived.

Western United States: This section has suffered serious population losses, particularly in the Rocky Mountains, several areas of California and the Pacific Northwest. The first edition of RIBBIT, a research newsletter on frog, toad and salamander declines in the west, lists several endangered populations, ranging from inhabitants of forests to those that dwell in lowlands and mountains. Threatened mountain-dwelling species include the boreal and Yosemite toads, the cascade frog and the tiger salamander. Waning forest frogs include Ascaphus truei and several types of the leaf-breeding Plethodon. Three lowland frog species may now be extinct -- Rana fisheri, R. onca and R. tarahumarae.

R. Bruce Bury and P. Stephen Corn of the U.S. Fish and Wildlife Service in Fort Collins, Colorado, prepared RIBBIT, relying on data from their own work and several other studies. In their survey of 105 locations in the central Rocky Mountains previously known to contain amphibians, the researchers note that the leopard frog inhabits only four of 33 sites where it once abounded, and the boreal toad is now seen in just 10 of 59 areas it had frequented. Acid rain does not appear to play a major role in the declines, Bury and Corn add. Three other species -- tiger salamanders, wood frogs and chorus frogs -- did not experience major regional losses during their three-year study, which ended in 1988. The scientists recently established Frog Net, an electronic communications system, to gather further information on amphibian declines in the West.

The California red-legged frog and the foothill yellow-legged frog, which live in California lowlands, have both suffered severe declines, in part due to the practice of stocking lakes with fish that eat tadpoles, notes Mark R. Jennings of the California Academy of Sciences in San Francisco. And in some areas of southern Oregon and Washington, the cascade, western spotted and red-legged frogs have virtually vanished, says Andrew R. Blaustein of Oregon State University in Corvallis.