Fungal Enemy Could Explain Worldwide Amphibian Die-off

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Fungal Enemy Could Explain Worldwide Amphibian Die-off

August 27, 2001 8:15 CDT

A large group of scientists now believes that a development of a new form of

fungus could explain the mystery of amphibian die-offs throughout the world.

Amphibians on six continents - Africa, South America, Central America, North

America, Europe, and Australia and Oceania - have been reported as infected

by the amphibian chytrid fungus.

Amphibians like frogs, toads, salamanders, and newts, act as sentinels for

global environmental degradation, and over the past 30 years, amphibian

population declines have been reported worldwide. This is the first wildlife

disease to be detected on a global scale that affects an entire class of

vertebrates and is associated with mass mortalities, population declines,

and species extinctions, according to Daszak of the Institute of

Ecology, University of Georgia. International efforts are ongoing to

determine how extensive and virulent the chytrid fungus is.

The fungal disease chytridiomycosis was first described in 1998 from the

study of adult amphibians collected at sites of mass deaths in Australia and

Panama from 1993 to 1998. In the meantime, to protect remaining amphibians,

countries and zones within countries should be classified as free of or

infected with chytridiomycosis, said an international group of amphibian

experts last August after a workshop in Australia.

A case detection and recovery is going on in Colorado as state wildlife

biologists use tiny high-tech transmitter locators to help boreal toads

fight the deadly fungus. Colorado amphibian researchers have found that the

chytrid fungus can be blamed for the decline of boreal toads usually found

around the state's beaver dams and meadows. For decades, their disappearance

left Colorado biologists baffled. The devastating losses apparently began in

the late 1970s and continued through the early 1980s. During that period,

Colorado Division of Wildlife biologists estimated that as much as 85

percent of the state's boreal toad population was wiped out.

Unlike many species whose decline could be related to the loss of habitat,

there were no obvious changes in many of the places boreal toads inhabited.

But between 1986 and 1988, the number of known boreal toad breeding sites

fell from 59 to 10. Then in 1999, while working with Dr. Green at the

National Wildlife Health Center, Colorado Division of Wildlife researcher

Mark found the existence of a chytrid in Colorado and linked it to the

toads. " Normally these chytrid fungi just live off of dead plant material

and are fairly common, " said. " But apparently they have evolved into a

new species of fungus that attacks living amphibian flesh. By the mid-80s it

appeared that (the toads) were well on their way to extinction, but now

we're finding a couple of new sites every year, " said. " Part of the

reason is our intensified surveying efforts, so whether or not they will

survive in the wild is still in question. "

While the toads have not really made a comeback, the populations seem to

have stabilized, says. This spring and early summer, was able to

find toads at 56 sites, which led him to believe that their chances of

long-term survival are improving. Meanwhile, Colorado biologists have

established a breeding population of more than 1,000 toads at the Mumma

Endangered Species Hatchery in the San Valley that will be used to

repopulate areas that once supported boreal toad populations. " We have

captured toads from 18 different sites to guarantee genetic diversity, " said

Craig Fetkavich, a Colorado biologist who is overseeing the effort. Boreal

toads don't reach sexual maturity for four-to-six years, Fetkavich said, so

he is now in the process of artificially manipulating the hours of sunlight

the toads receive to see if it is possible to speed up the age at which they

can start producing young.

When that happens, potential sites will first be tested for the presence of

chytrid fungus. Those sites that are clean will be used to reintroduce the

toads, which will be monitored to evaluate their recovery. Right now it

appears that the fungus is not wiping out amphibian populations but only

suppressing them. The ability of the toads to develop a natural defensive

mechanism to combat the fungus remains to be seen.

Source: ENN

Cosmiverse Staff Writer