Endangered toads gaining traction in Colorado mountain wetlands: "A really big deal"

Wildlife biologists recently discovered rare toads are naturally repopulating in a high mountain lake where captively raised tadpoles were transplanted for several years.

Staff from the Colorado Parks and Wildlife found boreal toad tadpoles in a marsh above the town of Pitkin in July. 

"This is a really special day. We have been reintroducing toads at this site since 2018, and this is the first time that we have observed wild reproduction occurring" as a result of the transplanting program, CPW Southwest Region Native Aquatic Species Biologist Dan Cammack stated in a press release. "It's a really big deal."  

It's only the second location in Colorado where the toads populations are on the rise. The other is near Cameron Pass. Officials confirmed natural breeding there a decade ago.

The boreal toad is a native to Colorado's wetlands. But the amphibian's numbers have been decimated the last 20 years by habitat loss and more significantly by the chytrid fungus. 

The National Institute of Health calls chytrid fungus "one of the biggest threats facing amphibian species and population survival worldwide." The most recent data suggests the skin disease has led to the extinction of 90 species of amphibians and to population decline in another 500. Its spread is believed to be the result of global live animal trade.

Wildlife officials estimate there may be as few as 800 wild adult boreal toads left in Colorado.     

The boreal toad is presently listed as an endangered species by the states of Colorado and New Mexico and is a protected species in Wyoming.  

CPW has stocked an estimated 20,000 tadpoles at the Pitkin site in the last six years. Six years is the approximate time a female boreal toad requires to reach reproductive maturity.   

This year's discovery of wild tadpoles gives Cammack confidence the Pitkin toads will continue to reproduce in the future.

"For years, we have been watching multiple age classes thrive at this site, so we had high hopes this was going to become a self-sustaining breeding population and a successful translocation," he said. "This is the first year we've seen breeding occurring in this wetland, and it is evidence of that success.

"This day is a culmination of a lot of dedicated people's efforts, including multiple biologists, technicians and hatchery personnel. Everyone who has been involved in this project has poured their heart and soul into it. That's what it takes to get here."

The majority of tadpoles were raised at CPW's Native Aquatic Species Restoration Facility near Alamosa. The effort started with a collection of boreal toad eggs collected in the wild.

The Alamosa facility opened in 2000. A dozen endangered fish species are captively bred and raised here alongside the boreal toads. CPW claims it is the only facility of this type on the continent. 

Ninety-five boreal toads from the Alamosa facility were given to the Denver Zoo Conservation Alliance in 2021. The zoo has successfully bred and raised its own brood of tadpoles. 

A month before Cammack's visit to the Pitkin area, DZCA contributed its own batch of boreal tadpoles with those from CPW. Staff in June poured 2,200 boreal tadpoles into a marshy area near Creede, a site CPW chose for reintroduction after a wildfire in 2013. It was the zoo's second batch of tadpoles; the first went into the waters near Pitkin in 2022. 

The Denver Zoo Conservation Alliance has 18 years of experience raising other endangered amphibians. It became the first zoo in the Northern Hemisphere to successfully breed critically endangered Lake Titicaca frogs, and has since provided more than 250 healthy frogs to zoos and aquariums in the U.S. and Europe. In 2021, the organization successfully bred critically endangered Panamanian golden frogs as part of the Association of Zoos and Aquarium's Species Survival Plan. 

Jake Zubie, a zoo spokesman, called the boreal toads "an intrinsic part of the food web and important to the biodiversity of their habitat." He said amphibians in general are important bioindicators for the overall health of an ecosystem.

Cammack called them resilient. 

"We are up at 11,500 feet, at timberline practically. They gut out big winters covered by multiple feet of snow and experience only three to four months of warm growing season," he stated. "They are an integral part of the landscape, as far as I'm concerned. They were ubiquitous once in Colorado in this habitat. With chytrid fungus now being the primary cause of decline, we don't have that many populations of boreal toad remaining. For us to get something else going here is really important."