National Geographic : 1993 Apr
Earth Almanac Why Are Frogs and Toads Knee-deep in Trouble? he sleepy croaking of pond music is growing faint. Frogs and their kin are mysteriously vanishing, and scientists suspect human alteration of ecosystems is partly responsible. On five conti nents 19 countries have found mas sive die-offs among amphibians. "Frogs are good indicators of environmental change. With highly permeable skin, they are very suscep tible to toxic substances on land and in water," says James Vial, interna tional coordinator of the Declining Amphibian Populations Task Force. Costa Rica's golden toads once gathered to mate en masse (above) but have not been seen since 1989. Decreasing rainfall may be a factor. Discovered in 1973, one of two species of Australian gastric brood ing frog vanished seven years later; the other disappeared in 1985. The female swallowed her fertilized eggs and incubated them in her stomach until the froglets hopped out (far right). While brooding, she stopped HYLAANDERSONII, DOUGWECHSLER,ANIMALSANIMALS producing stomach acid-an ability that interests ulcer researchers. Its numbers plunging, the north ern leopard frog (bottom left) suffers as wetlands are drained in North American prairies. Habitat loss threatens the Pine Barrens tree frog (left) in New Jersey. Scientists are examining sus pected causes. With support from RHEOBATRACHUSSILUS, M. J . TYLER, AUSTRALASIAN NATURETRANSPARENCIES the National Geographic Society, Andrew Blaustein of Oregon State University is investigating whether increased ultraviolet radiation due to ozone depletion is killing western toads in the Cascade Range. Last year he found 2.5 million eggs; 95 percent of the embryos were dead.