Year of the Frog

Three White\'s Tree Frogs, sitting on a stone
A behind-the-scenes visit to the National Zoo in Washington, D.C. allowed us to come face to face with these White’s Tree Frogs, which are housed in the zoo’s Reptile Discovery Center. They look a little bit like buddha statues, and when I saw three of them sitting all together like this, I laughed.

Photo copyright Bennett S. Garvin.

But there’s not a lot of reason to laugh about frogs these days, because many of the world’s amphibians are threatened species. For the last thirty years or so, scientists have noticed a drastic decline in frog populations worldwide. During that time period, as many as 122 species of frogs may have become extinct.

The causes of the extinctions and population declines were considered to be loss of habitat due to human development, pollution, invasive plant and animal species that crowded out the native frogs, and climate change. But in the 1990s, scientists discovered a fungus that may be repsonsible. This Chytrid Fungus, and it causes a disease called chytridiomycosis in amphibians. In short, many of the animals are dying because they’re sick.

Some scientists think that the chytrid fungus originated in Southern Africa and was transmitted unknowingly by the frog trade. Since the 1930s, frogs such as the African clawed frog have been used in biomedical research and testing. Frogs were collected in the wild and shipped to laboratories around the world. And they took the chytrid fungus with them. Some of these frogs escaped from captivity and infected the local amphibian populations, which had little or no resistance to the fungus.

This is not to say that habitat loss and pollution issues aren’t issues. Animals such as frogs are often viewed as environmental indicators; that is, anything that is wrong with the environment will show up first in frogs and other small animals. Water pollution is thought to be one factor responsible for a number of frog mutations found in recent years. Scientists don’t know the whole story yet; they think that high levels of UV radiation and parasites may also be causal factors.

Zoos and aquariums around the world are attempting to address the problem of amphibian decline by breeding many of the frog species in captivity. Frogs aren’t the only animals affected — so are salamanders, newts, and caecilians, animals that resemble large worms. One of the species currently being bred in captivity is thePanamanian Golden Frog. If you are so inclined, you may help the conservation effort of the National Zoo by adopting a Panamanian Golden Frog.