Toadally extinct? Not if zoos can help it.

Puerto Rico's crested toads, Peltophyrne lemus, have had a tough time adapting. Only two populations of this species remain on Earth -- one north and another south of a mountainous divide. In recent years, biologists have spotted only about 25 of the northern toads, says Robert R. Johnson of Canada's Metro Toronto Zoo. Even the genetically distinct southern population of up to 3,000 crested toads may face extinction, he says. In hopes of restoring the toads' natural abundance, Johnson is directing a species survival effort -- the only such program that the American Association of Zoological Parks and Aquariums has undertaken for amphibians.

Johnson is currently drawing up reintroduction plans for some 600 captive-bred tadpoles being nurtured at seven zoos, including his own -- all the offspring from a single northern P. lemur couple. "We're trying to breed every [captive] animal that we have," he says. Of nine pairings tried, only the one couple, at the Cincinnati Zoo, succeeded in producing young. In about two weeks, Johnson will fly their thumbnail-sized toadlets "home" -- to a concrete, walk-in cattle trough, the last known breeding site for Puerto Rico's northern crested toads.

How the newcomers will fare is anybody's guess. Cattle still water at these troughs, Johnson notes. Moreover, "spraying of nearby pastureland for cattle ticks may result in high levels of pesticides in field runoff [of rains], which is the only source of water for the troughs," he says. Wild toads also suffer predation by lizards, birds, mongooses and rats. As a result, Johnson says, the success of captive-release programs "must be considered in a time frame of perhaps 10 or more years and after a number of releases."