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Bogs and boreal toads: Hunting for killer fungus

Bob Berwyn
Summit correspondent
Colorado Division of Wildlife researcher Kevin Rogers scans a pond near Dillon Reservoir for chorus frogs. The biologist was leading a training session for a group of prospective boreal toad surveyors. Summit Daily News photo/Bob Berwin.
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A BOG IN SUMMIT COUNTY ” To the few passers-by on the rec path Wednesday, it must have been a strange sight: 10 of us, decked out in shiny new knee-high boots, blue surgical gloves and carrying white five-gallon buckets.

Standing shin-deep and bent over at the waist in a murky pond near Dillon Reservoir, I plunged my arm up to the elbow into the cold water and made a grab for an elusive amphibian.

“Whaddya lose?” asks one cyclist, stopping for a minute under the gray, sputtering skies.

“We’re trying to catch chorus frogs,” I answer, studying the waterlogged strands of decaying grass for jelly-blob egg masses and listening for telltale frog chirps.

“You’ve got to think like a heron,” says Kevin Rogers, a biologist. “Get poised, and then move fast,” he says, explaining the best techniques for catching the fast-moving amphibians.

Rogers, a Colorado Division of Wildlife researcher, wants at least 20 frogs captured from this area to test for a chytrid fungus that’s been tabbed as a key factor in global and local amphibian declines.

Each specimen gets its stomach swabbed 25 times with a sterile cotton swab. The samples are sealed and sent off for DNA testing, and the frogs are released unharmed.

The best time to capture the cold-blooded critters is at night, he says, when you can spot their eyes reflecting the glow of a flashlight just above the surface of the water. He says searchers can also go high-tech, using laser-pointers to triangulate on the gentle croaking, which sounds a little like a finger running along the teeth of comb.

Wednesday’s search ended in a shutout win for the home squad, as chilly weather sent the frogs hustling for deep cover, burrowing into the muck and clumpy grass at the edge of the ponds.

Despite a couple of sightings but no catches, Summit County’s newest toad-tracking team is not discouraged. It’s only spring practice ” the real game begins next week, with methodical surveys for boreal toads in Cucumber Gulch, near Breckenridge.

The goal of the study is to discover if a remnant population persists at a historically documented breeding site and to determine whether the amphibian-killing chytrid fungus is present.

With superb habitat for boreal toads in the dynamic beaver pond complexes, wildlife biologists may even consider Cucumber Gulch as a potential reintroduction site. That is, once they know more about the fungus and whether some strains of toads have a genetically inherited resistance.

Testing chorus frogs for the fungus in the ponds between Frisco and Dillon helps establish the overall presence of the pathogen in the area, Rogers explains, adding that it’s also a good training session for toad hunters, since the chorus frogs are much faster and trickier. By comparison, the boreal toads lumber through the muck and grass ” “You can walk right up to them,” Roger says.

Consistent monitoring over time will show a dynamic picture of how fungus and toad populations change over time and distance. The Summit data, as part of a bigger picture, could show where the wave will move next, potentially giving those areas time for preparation.

The wildlife division has been intensively monitoring boreal toad sites locally and around the state for several years, so some baseline data already exists.

Rogers’ pondside seminar also includes a briefing on methodology and protocol. The emphasis is on making sure that the fungus isn’t inadvertently transported by the researchers (thus the surgical gloves, as well as a boot-bleaching session).

It’s an ongoing concern as biologists try to learn how and why an astounding number of amphibian species have crashed in the span of just a few decades.

With my nose just a few inches from the shimmering water, I study a partly decayed aspen leaf, floating translucently on the glassy surface. Starting as a gentle ripple in the serene reflection, a bigger picture emerges. It becomes more clear how this Summit County hunt for an inch-long frog fits in to an effort to better understand a wave of species extinction sweeping across the world like a biological tsunami.

Why should we care if boreal toads live in Cucumber Gulch, or whether they are dying because of the chytrid fungus? Why are we going to spend hours and hours wading though murky bogs, spending thousands of dollars, to find out?

There are, of course, more-or-less obvious implications of endangered species laws and related land-use regulation tools. That includes day-to-day management of Cucumber Gulch to protect boreal toad habitat.

But it’s not clear how crucial the amphibians are to the ecosystems of high country ponds, Rogers says. They don’t appear to be a critical food source for any predators, nor are their numbers high enough to be a factor in controlling any other species ” ants seem to be the preferred food for boreal toads, he adds.

What we do know is that nearly 32 percent (1,856) of all the world’s known 5,743 amphibian species are considered threatened. By comparison, only about 12 percent of the world’s bird species and 23 percent of mammal species are threatened, according to a recently completed Global Amphibian Assessment.

The ambitious three-year study analyzed data from 520 scientists in more than 60 countries, providing a baseline for monitoring and conservation strategies aimed at stemming the loss of amphibian populations. The peer-reviewed results were published in scientific journals and recognized as an important first step in cataloging an entire class of species on a global scale.

Pinpointing chytrid-free areas and establishing populations of fungus-resistant amphibians in Colorado could be a big part of such a conservation strategy, Rogers says.

The division of wildlife has taken the lead in some areas, establishing an aquatic breeding facility and experimenting with amphibian populations to determine whether genetic resistance is a survival factor. And, Rogers says, an experimental boreal toad reintroduction project on Grand Mesa outside of Grand Junction is one of the very few attempts he knows of worldwide to implement a field conservation strategy.


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