Chytrid Fungus and Amphibian Declines

Chytrid Fungus and Amphibian Declines

The chytrid fungus is devastating frogs in North and South America and in Australia. All continents which have populations of frogs now too have the chytrid fungus. It has been found in more than 40 countries and in 36 states in the United States. The disease can survive from sea level to 20,000 feet in elevation.

Studies show that the chytrid fungus has been around for a long time, but now something has changed to make the fungus lethal. One theory is that climate change, ozone depletion, or pollutants could increase the animals’ vulnerability to this disease. Add to these factors habitat destruction, introduction of exotic species, and over exploitation—and you have, as reported in National Geographic Magazine, what University of California Berkeley biologist David Wake calls “…death by a thousand cuts.”

There is much focus on finding ways to save more species in the wild, but for those under imminent threat, an international effort called Amphibian Ark is underway to keep captive populations of some 500 amphibian species that would otherwise become extinct—in zoos, in aquariums, and other refuges—to be reintroduced at some future time if the threats can be mitigated. To learn more about Amphibian Ark, click here.

Whatever the cause, the declines are especially alarming because amphibians are an indicator species, an early warning system of environmental health, due to their sensitivity to air and water pollutants and changes in environmental conditions such as climate change and increases in ultraviolet radiation. And the far north is not exempt. Along the coast of Alaska, boreal toads—Alaska’s only toad species—have gone from abundant to almost non-existent in less than ten years. The cause remains uncertain, but biologists have found boreal toads in southeast Alaska and in other states that died from the chytrid fungus.

So far, wood frogs remain common in Alaska and many parts of North America. In Rocky Mountain National Park for example, wood frogs carry the chytrid fungus, but they still maintain a strong population. However, the formerly abundant leopard frogs have completely disappeared from that area. And in 2002, a dead wood frog was found with the chytrid fungus in Kenai National Wildlife Refuge on the Alaska coast.

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