Something is killing frogs all over the world. The list of suspects includes acid rain, pollution, and vanishing wetlands. But the real killer may be none of the above. A team of biologists suspects that a previously unknown fungus may be at least partly responsible for the global decline of frogs.
Last year researchers discovered that a microbial parasite was infecting the skin of dying frogs in Panama. A similar microbe turned up in Australia, but no one could positively identify it. Now D. Earl Green, of the National Institutes of Health, and Karen Lips, a biologist currently at Southern Illinois University, along with researchers in Australia, have announced that the frog-killing parasite is a fungus.
To date the researchers have found the fungus in about 30 frog species from Australia, Central America, and the United States and have shown that it kills frogs in laboratory trials. The fungus attacks the frogs' skin, says Green. Since frogs drink and breathe through their skin, the fungus may be suffocating and dehydrating them.
The fungus, apparently a new species of aquatic chytrid fungi, has yet to be named. Chytrid fungi have not previously been found to parasitize vertebrates, says Green, but some live freely in water or soil and attack plants and insects. The fungus may have been newly introduced to frog habitats, or environmental changes may have made the frogs susceptible to a parasite they had previously resisted. "Maybe the fungus got stuck on a shoe or a camera tripod of an American tourist, or even in the digestive systems of birds, and was brought in. It's not certain," says Green. "But we do know that the disease is spreading by as much as 19 miles a year in Panama."