The eastern boreal toad population in the high elevations of Colorado and other Rocky Mountain states may be in decline, but it will not be granted protected status under the national Endangered Species Act.

The U.S. Fish and Wildlife Service, operating under the umbrella of the Department of the Interior, announced Thursday its rejection of 25 species from threatened or endangered listing, including the subalpine amphibian. Within the federal agency’s Mountain-Prairie Region, the Great Sand Dunes tiger beetle and Northern Rocky Mountain fisher were under review for protection as well, but were also left unlisted.

Distinguished by its wart-covered skin, the roughly 4-inch adult toad that takes to marshes, streams and glacial ponds requires several widely distributed populations throughout its variety of wet habitats to avoid extinction. But a harmful fungus known as chytrid is threatening the survival of amphibians worldwide, and this subspecies of the western toad in particular.

“The Service anticipates the eastern population will continue to maintain self-sustaining populations across its range for the next 50 years,” stated a Fish and Wildlife Service news release. “Because of these findings, the Service found the eastern population of boreal toad is not warranted for listing under the ESA.”

The decision reverses a positive initial finding made by the agency following a three-month research study in 2012 after a consortium of wildlife advocacy groups led by the Center for Biological Diversity petitioned the listing. A subsequent yearlong analysis found a large percentage of the boreal toad population has moderate-to-high resiliency to the often fatal disease caused by the fungus, and thus “has a very low risk of extinction.”

The petitioners, who also requested a number of other species designations that were denied and are still awaiting verdicts on more, firmly contest the recommendation.

“The decision not to protect that toad is just ridiculous,” said Noah Greenwald, endangered species director for the Center for Biological Diversity. “It’s really clearly endangered, because of chytrid fungus and habitat destruction. U.S. Fish and Wildlife even stated chytrid has already taken out something like half the population. It just doesn’t make any sense.”

A Fish and Wildlife Service Mountain-Prairie Region spokeswoman explained that all endangered listing decisions are made using a standardized species status assessment — a science-based analytical approach that evaluates probable future scenarios of environmental conditions and conservation efforts. A worst-case scenario population model employed by the agency suggested “a greater-than-95 percent probability of persistence.”

“I fully, fully believe that model, it’s state of the art,” said Harry Crockett, Colorado Parks and Wildlife’s statewide native aquatic species coordinator. “If the Fish and Wildlife Service is asking if the species is in danger of extinction or extinction in this part of the range specifically, then the answer is no. That does not say that things are going to be peachy, it means we still have a lot of work to do.”

Reintroductions of boreal toads raised in captivity, he said, on top of habitat restoration, are other strategies. Creating increased tolerance to chytrid in both wild and farmed populations with what is basically a probiotic vaccine could also help the population. After more than two decades of fieldwork on the species with other states, as well as university researchers, Fish and Wildlife, the Bureau of Land Management and the U.S. Forest Service, Crockett said results are promising in improving toad survival and perhaps even expansion.

The great unknown, as both the advocacy groups and state wildlife agencies point out, remains what impact climate change may have on at-risk species like the boreal toad. For example, seasonal shifts from warming temperatures or reduced snowpack could diminish the vital wetlands areas where the toad breeds and further hurt its ability to persist in viable numbers. Conversely, wetter winters could raise the chance of the deadly fungus living longer and spreading further — no one can say for certain.

“The possible effects of climate change, there’s going to be effects, but it’s kind of equivocal on what they’ll be,” said Crockett. “We’ve looked at climate models that predict it might increase their active season by as much as a month, which could actually help the toads. On the other hand, less precipitation could certainly hurt them.”

It’s these questions the wildlife nonprofits plan to examine and pose as they consider suing the Fish and Wildlife Service over the decisions on the boreal toad and several other species denied protection this week. Waiting to see how the amphibian performs in the coming years before again petitioning for endangered status could be another course of action.

“We definitely could challenge the decision in court,” said Jenny Loda, a wildlife biologist and attorney specializing in amphibians and reptiles for the Center for Biological Diversity. “We need to look a lot more at the background for how the decision was made. The Fish and Wildlife Service is pretty bogged down and underfunded, and has a lot of other species to work on — both currently listed and others being considered for listing. I don’t think it’s too likely they’ll suddenly list it on its own.”