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Once-common toads still in decline

Bob Berwyn

SUMMIT COUNTY ” Although federal biologists decided for now to keep boreal toads off the endangered species list, a recent amphibian conservation summit in Washington, D.C. ended with a slate of proposals to mitigate human impacts on amphibian species.

Boreal toads, once common across the Rockies, have disappeared at a rapid rate in the past few decades. Summit County still harbors several breeding populations, monitored carefully by Colorado wildlife experts.

This summer, researchers combed wetlands in Breckenridge for signs of the elusive amphibians, but found only two toads in an area where they were once common, according to longtime residents.



In other parts of the state, biologists have made progress toward re-establishing boreal toads even in areas where a killer fungus is present. Some strains of boreal toads apparently have some built-in genetic resistance to the fungus. Those animals could help boost populations in suitable habitats.

The D.C. conference was convened by the Species Survival Commission of the World Conservation Union, with scientists declaring that, “It is morally irresponsible to document amphibian declines and extinctions without also designing and promoting a response to this global crisis.”



Nearly one-third of the world’s amphibian species are facing extinction. That compares with a rate of one in every eight species of birds and one of every four mammal species. The scientists said that at least 122 amphibian species have gone extinct since 1980, with about 43 percent of all amphibious species having experienced population declines during that time.

While attention in Colorado has focused on the killer fungus as the primary threat to boreal toads, habitat destruction is still seen as the main problem worldwide, said to Jim Collins, chair of the Declining Amphibian Population Task Force.

“Amphibians often occur in relatively small areas and are more susceptible to extinction due to habitat loss or degradation than most other vertebrates,” Collins said. “The extinctions show a weakness in current strategies for biodiversity conservation. Habitat conservation is essential but not sufficient. Existing protected areas alone are not sufficient to protect amphibians from a growing array of threats.”



The fungus is quickly spreading across new regions and scientists are calling it “the worst infectious disease ever recorded among vertebrates in terms of the number of species impacted, and its propensity to drive them to extinction.”

In other toad news …

At the end of September, researchers at Vanderbilt University in Tennessee announced that chemicals in frog skins are powerful blockers of HIV infection. The findings could potentially lead to topical treatments to prevent transmission of HIV ” and underscore the importance of preserving the planet’s biodiversity, according to conservation biologists.

“We need to protect these species long enough for us to understand their medicinal cabinet,” said Louise Rollins-Smith, Ph.D., associate professor of microbiology and immunology at Vanderbilt in an interview with the Environmental News Service. Rollins-Smith has been studying antimicrobial defenses of frogs for six years.

Frogs secrete large amounts of anti-microbial peptides, small protein-like molecules, when their skin is injured or in response to alarms. The peptides fight pathogens like bacteria, fungi and viruses.

The Vanderbilt researchers found 15 different peptides in a variety of frog species that show potential for their ability to block HIV infection without harming T-cells. The peptides appear to selectively kill the virus by inserting themselves into the outer HIV membrane and causing the virus particle to fall apart, the researchers explained.

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