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A fungus threatens survival of the only toads that live high in the Rocky Mountains

Biologists devised a treatment they hope will save the boreal toad, but first they must catch the tiny creatures to determine if their plan will work

A yearling boreal toad gets a shower after being found in an alpine wetland above Buena Vista. Biologists are racing to save boreal toads from a fungus that is killing off amphibians across the world. (Nina Riggio, Special to The Colorado Sun)
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BUENA VISTA — Tim Korpita is wearing blue rubber gloves and thigh-high waders, but when someone shouts “Toad!” he lunges like a ninja. 

He takes a giant step over the marsh grasses and is on his stomach at the edge of a slow-moving creek, clutching a tiny, speckled boreal toad between his thumb and index finger. He immediately turns the inch-long creature, checking for a green or pink spot on its inner thigh. 

Nothing. 

Korpita, a University of Colorado doctoral candidate, and Colorado Parks and Wildlife biologists last summer captured 250 boreal toadlets — beyond tadpoles but not quite terrestrial toads — in a high-elevation wetland along Cottonwood Creek. They injected them with a spot of either pink or green dye, visible through amphibian skin when held up to the sunlight. 

Pink was the control group, while the green-tagged toads received antifungal bacterial baths that scientists hoped would protect them from a pathogen killing off boreal toads throughout the Rocky Mountains. The disease is killing amphibians across the globe as biologists race to stop it before it’s too late.

Tim Korpita searches for boreal toads in thick marsh grasses in the Cottonwood Creek drainage above Buena Vista in late June. Korpita treated the toads with a bacterial wash last summer in an effort to protect them from a fungus that is killing amphibians worldwide. (Nina Riggio, Special to The Colorado Sun)

Korpita, 29, and a parks and wildlife crew returned to the mountains above Buena Vista on a recent blue-sky day, hoping to find at least some of their study group.

By lunchtime on toad hunt day, after nearly two hours of peering along the edges of mountain ponds and in the mud-bottomed streams flowing through the bog, the team had found just six yearling toads. They spotted five more that afternoon, gently placing each one in a plastic bag with a clump of moss for moisture.

Of the 11, just two were tagged (one pink, one green), meaning there was little to say about whether a bath last summer in the lavender-tinted wash, dubbed “purple rain,” is saving their lives. 

But this was biologists’ first trek of the summer. Colorado Parks and Wildlife and CU scientists plan to return every two weeks to the Chaffee County marsh to catch the black-and-gray toads and swab their skin for DNA before releasing them back to the pond. Each one, tagged or not, is showered with sterile water to rinse off the mud and placed in a large test tube for exactly one hour to collect a sample of the bacteria on their skin.

Meanwhile, on Korpita’s recent trip to the ponds, he sits under the shade of a pine tree in the middle of the forest and showered the first batch of captured toads. With a cotton swab, he strokes their clean skin for DNA samples. Back at the lab, Korpita will try to determine whether the toads carry the deadly chytrid fungus. And for the toads that received last summer’s fungus-fighting bacteria treatment, Korpita will try to see if it’s still active in their skin and protecting them from the disease. 

The hope is that by summer’s end, Korpita will have captured enough toads that received his bacterial bath to know whether it works in the wild. 

The tedious effort is one of many underway to save boreal toads, the only high-elevation toad in the Rockies. The slow-moving toads — listed as an endangered species in Colorado — can hibernate beneath the snow for six to eight months of the year, at elevations from 7,500 to 12,000 feet.

A team from Colorado Parks and Wildlife and the University of Colorado is trying to catch as many yearling boreal toads as possible this summer to determine whether a fungus-fighting bacterial bath they were given is saving their lives. The toads were bathed in the bacterial wash as toadlets last summer. (Nina Riggio, Special to The Colorado Sun)

Boreal toads were so abundant, from the late 1800s and until the 1960s, that they would sit under Buena Vista lamp posts at night, gobbling up insects that swarmed to the light, according to historical articles reviewed by Parks and Wildlife. They live in Montana, Wyoming, Idaho, Alaska, Utah, Colorado and, until they died off there, New Mexico. 

The first signs of the fungal disease appeared in the 1980s and 1990s, killing off entire populations of the croaking creatures in otherwise-pristine alpine bogs that had been their home for decades. The toads began disappearing from marshes above Gunnison in the 1990s. 

The fungus — which has the scientific name Batrachochytrium dendrobatidis, or Bd — is killing off amphibians all over the world, from Australia to South America to the Korean Peninsula, which, under one theory, is where it originated. High-elevation amphibians, including the boreal toad, are particularly susceptible. 

Chaffee County, though, was so full of boreal toads that biologists wondered if the Cottonwood Creek drainage had some special resistance to the amphibian plague, said Scott Schneider, a biologist with the Colorado Natural Heritage Program, which has been capturing and counting toads for years for the parks and wildlife department. 

Scott Schneider, with the Colorado Natural Heritage Program, has been catching and counting boreal toads for years. He first detected the fungus in Cottonwood Creek toads in 2013. (Nina Riggio, Special to The Colorado Sun)

The bog above Buena Vista was so packed with boreal toads that Schneider could catch them one after another for hours, particularly during breeding season when toads congregate in ponds. One night in 2011, he caught 165 toads. 

The point was to check them for the dreaded fungus, and they all came up clear.

Until 2013. One toad out of dozens collected tested positive for the fungus, which infects skin cells and creates a collection of spores called a “zoosporangia” on a toad’s skin. Then the zoosporangia bursts, sending swimming zoospores into the pond to infect other toads. 

“It was devastating,” Schneider said. “We were hoping it was just a false positive. And then the next year we got a bunch of positives back.” 

Since the fungus reached Chaffee County, the highest count from one of Schneider’s many hunts is just 11 toads.

The loss of the boreal toad isn’t just about the toad; it’s about the ecological stability of the forest, said Paul Foutz, native aquatic species biologist for the Southeast Region of Colorado Parks and Wildlife. The toads lived in Colorado before humans, he said. They eat mainly insects, and are food for snakes, birds and small mammals, including weasels. 

“As we remove those little pieces of the puzzle, we have less stability in our ecosystem,” Foutz said. 

Paul Foutz is a native aquatic species biologist for the Colorado Parks and Wildlife Department. This week, he’s helping take nearly 6,000 hatchery-raised tadpoles to Browns Creek. (Nina Riggio, Special to The Colorado Sun)

Korpita’s research, funded by the parks and wildlife department, is just one of several efforts to save the toads. This spring, Colorado Parks and Wildlife took egg sacks from the Cottonwood ponds and brought them to a hatchery in Alamosa, where they hatched into tadpoles.

The hatchery-raised tadpoles — and there are nearly 6,000 of them — will receive antifungal bacterial baths before they are released into the mountains near Nathrop this week. Packed into plastic bags filled with water and carried three miles by backpackers, they are headed for Browns Creek.

The area in Chaffee County once teemed with boreal toads, but now there are none. Scientists haven’t detected the toad-killing pathogen at Browns Creek, which makes it an ideal spot to reintroduce them. Still, they aren’t sure why the toads left the area. 

In a separate effort, the Denver Zoo released 620 boreal toads in remote southwestern Utah in June. The toads, hatched at the zoo, were released in the mountains in the hopes of boosting the population in the wild.

An adult toad, estimated at 5 years old, is captured for testing above Buena Vista at the end of June. Biologists are trying to save the toads from a fungal infection that is killing off amphibians around the world, including salamanders and newts. (Nina Riggio, Special to The Colorado Sun)

Colorado and neighboring states in the 1990s formed the Boreal Toad Recovery Team, which includes the parks and wildlife department, U.S. Forest Service, the National Park Service, the Bureau of Land Management and others. State biologists do not know just how many toads are left, but said the population has gone from abundant to scarce, rapidly.

At this time of year, boreal toads are hiding from snakes, so good luck spotting a yearling in the mud at the edges of an alpine pond. 

“You would maybe see like a mouth and a couple eyes. Probably not their body. Maybe their front legs,” advises Korpita as he scans the wetland. Watch every step, he says, so you don’t accidentally squish one. Or step in a pile of moose droppings.

Korpita’s twin brother, Dan, a P.E. teacher from Massachusetts, is along for the hunt. “I feel like I’m in a lot of good spots where I’d be if I were a toad,” Dan says, after searching for nearly an hour without finding one. 

Then a shout from a pond over the hill. “I heard a happy yowl coming from that way. I hope somebody found a yearling and didn’t just fall in the mud,” Tim Korpita says. 

“We got one, Tim!” someone yells through the bog. 

The yearlings are smaller than usual for this time of year, likely because they hatched later due to a longer winter with deeper snowpack. Their hardiness is what Korpita loves most about the creatures that are the subject of his doctoral thesis.

“It’s so cool how hardy they are to make it through a brutal winter,” he said. “The adaptation to  the high-elevation environment is pretty impressive for a cold-blooded thing. They are under snow for six, seven, eight months.”

A team from the Colorado Department of Parks and Wildlife and the University of Colorado prepare a boreal toad for testing during a late-June survey in an alpine bog above Buena Vista. (Nina Riggio, Special to The Colorado Sun)

Last summer, Korpita camped near the ponds for close to three weeks, occasionally driving out of the mountains to visit his wife. He kept each toad for about two weeks in plastic tubs — a day or two for a soak in the purple bacterial treatment and several more days to see if the fungus-fighting bacteria were staying on their skin.

“The actual treatment is pretty basic — at the right point, dunking in the water with the bacteria that we want,” he said. The best time is when the toadlets are in metamorphosis, turning from tadpoles that swim in water to toads that hop on land.

The bacteria in the wash are naturally found in toads, but in much smaller quantities. The idea is to boost the number of protective bacteria in young toads, giving them a better chance at survival. Boreal toads can live for 10 to 12 years.

The fungus has been around since evolutionary times, Korpita said, but the common scientific theory is that a “hybridization event” occurred in the last several decades that created a particularly virulent strain. It affects not just toads, but salamanders, frogs, newts and other amphibians.

The wash showed promising results in the CU lab, decreased mortality by 40 percent. But whether it will work in the wild, where the bacterial environment is not controlled, is another question, Korpita says. 

There is some indication it does. About a month after bathing the toads last summer, Korpita and a parks and wildlife crew returned and captured 10 toads that had been bathed. Lab tests showed the fungus-fighting bacteria was alive on their skin. 

If the wash works in nature, it could be a “game-changer” for the toads, said Foutz, whose job at parks and wildlife is to protect fish and aquatic species that are native to Colorado. The crew will return to the Chaffee County alpine ponds every other week the rest of the summer to find as many boreal toads as possible. “This is just the first of several trips,” Foutz said. “We hope to find more of them.”

Tim Korpita, a doctoral candidate at the University of Colorado, holds a boreal toad estimated to be 5 years old during a recent survey. Korpita is trying to save boreal toads from a fungus that infects their skin cells and spreads through pond water. (Nina Riggio, special to The Colorado Sun)
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