Recognizing Colorado Endangered Species Week
May 10 through May 16, 2020 is Colorado Endangered Species Week. This week is dedicated to the mission of educating the public and working towards the protection of the over 300 plant and animal species that are at risk in Colorado.
Under a blistering July sun, about 35 Colorado Parks and Wildlife (CPW) aquatic biologists, staff and volunteers hiked a steep mountain trail last summer, each loaded with large bags of water filled with 200 or so squirming, black boreal toad tadpoles.
In all, the hikers hauled some 5,600 tadpoles to an alpine wetland on Browns Creek at 9,780 feet, beneath the snow-tipped reaches of Mount White in Chaffee County.
Similar parades of CPW biologists, staff and volunteers have taken place to high-altitude wetlands as the agency pursues several avenues in its efforts to rescue the tiny brownish-black state-endangered toad. Boreal toads once thrived in Browns Creek and other Colorado high-country wetlands, but their numbers have been crashing due to a deadly “chytrid” skin fungus that is threatening amphibians worldwide.
The grueling 6-mile Browns Creek round trip was led by Paul Foutz, CPW native aquatic species biologist and boreal toad specialist, in support of University of Colorado PhD candidate Tim Korpita, who had set up a laboratory on the edge of the wetland. Korpita and several graduate students took possession of the bags of tadpoles and separated the squirming amphibians based on how far developed each was toward metamorphosis into full-grown toadlets.
After placing the tadpoles in tubs in the water, the team of scientists began preparing an experimental probiotic bath they’ve dubbed “Purple Rain” due to its purplish hue. In preparing the bath, they use bacteria native to the local biological community and naturally found on toads to increase the abundance of protective bacteria during a vulnerable life stage of the toads. Scientists hoped the fungus-fighting bacteria would establish on the amphibian skin and protect the toads.
Following hours of swabbing and mixing, the Purple Rain solution was suctioned from dozens of Petri dishes, collected in a large bottle and then carefully poured into the tubs full of tadpoles.
Then the scientists waited. The tadpoles needed to be bathed in the solution for 24 hours before they could be released into the wetlands, a historic boreal toad breeding site that is now absent of toads.
“This is a potential game-changer for boreal toads and amphibians worldwide,” Foutz said as he prepared to release a tub of tadpoles, which had sleek, black heads, long, translucent tails and tiny little legs. “It’s critical we find a cure to this deadly skin fungus that is killing our amphibians.”
The release of tadpoles went on for several days and marked the first large-scale field application of Korpita’s CPW-funded research in the McKenzie Lab at the University of Colorado-Boulder.
Korpita and Dr. Valerie McKenzie and their research team have spent three years investigating the use of bacterial treatments to armor boreal toads against the skin fungus. Similar experiments in a laboratory setting increased toad survival by 40 percent after bathing the toads in the probiotic treatment.
CPW staff and CU researchers will continue to monitor the tadpoles’ development and metamorphosis this coming field season. In July they hope to find yearling toads returning to the wetland, where they will reswab toads and check for the continued presence of the Purple Rain bacteria.
In March, Korpita gave a report on his research and the Purple Rain application at the Browns Creek wetland at the annual statewide Boreal Toad Conservation Team meeting.
He explained the Purple Rain solution had the potential to be more effective than simply dousing the toads in chemical treatments because probiotics are living microbes that take up residence on an amphibians’ skin, enhancing their natural ability to fight deadly fungus. Simple chemical treatments would quickly wash away and leave the toads unprotected.
“The skins of the toads are live, antifungal-producing factories,” Korpita said, “while chemicals would be gone pretty quickly.”
He described the process of swabbing the toads for DNA samples, identifying the bacteria living on the skin, amplifying it and producing a “proportional abundance” of the toad’s own protective bacteria.
He said the Purple Rain treatments were a “potential useful conservation tool” in the wild after multiple years of applications, mostly in Chaffee County.
In a secondary experiment in the Cottonwood Drainage, Korpita found treated individuals to have lower loads of chytrid bacteria than untreated toads, although treatments didn’t completely eliminate it.
“Last summer we learned we definitely can manipulate microbial communities in the field,” Korpita said. “The data shows it quite well.”
Exactly how long the treatments persist in the wild is difficult to determine because it’s hard to recapture treated toads, but the scientists worked diligently to overcome this through survey work in the treated wetlands. This is work they will continue this coming summer.
“We don’t have a great idea of persistence,” Korpita said.
One significant scientific discovery Korpita made through his work was how the microbial community on the skins of pre-metamorphosis toads is dominated by a single bacterial species. This bacteria appears to dominate the skin microbial community in eggs and developing tadpoles, appearing to out-compete even the native bacteria scientists used to treat the tadpoles.
“Now we’re studying why it is so dominant on the skin,” Korpita said.
That’s why timing is key to the application of the Purple Rain solution. If the tadpoles are treated too early, the probiotic solution is ineffective. It’s critical the solution is applied in the very final stages immediately before tadpoles lose their tails and transform into toads.
“At metamorphosis, that bacteria disappears rather quickly, leaving a small window when we can seize a more protected microbial community,” Korpita said. “A probiotic bath a little later in development ended up with a lot more protection on their skins. We saw this data repeated at Browns Creek.”
Unfortunately this lesson learned, revealed that many of the Browns Creek tadpoles were probably treated a little too early. Swab results from upcoming yearling surveys in the summer of 2020 will help confirm that.
Despite the success of the 2019 work, Korpita said questions remain about the direction of the research moving forward.
“Do we pursue a widescale probiotic application now that we know what that looks like now,” Korpita said. “And is it enough to fight off fungus? I think it requires more experimentation.
“Then there’s the question: Is Purple Rain the best bacteria option? There are other antifungal metabolites out there and maybe others out there are more effective. We have a few dozen other options in culture right now in the lab.”
So, the story will continue into the 2020 summer field season, as biologists from CPW join researchers from the McKenzie Lab to see if their stocking was successful, and if yearling toadlets return to the Browns Creek wetland.
Regardless of their findings, the resulting information gathered from years of work by these researchers and biologists will assist future conservation efforts of this state-endangered species.
Do you enjoy learning about conservation in Colorado?
Subscribe to Colorado Outdoors magazine. For more than 80 years, Colorado Outdoors has been the official magazine of Colorado Parks and Wildlife.
Article by Bill Vogrin. Bill is CPW’s public information officer for the Southeast Region. He’s based in Colorado Springs.