A Colorado push to euthanize mountain lions and bears as a predator-control experiment to revive declining deer is facing a barrage of criticism from scientists and conservation groups as state commissioners prepare for a Wednesday vote.

The latest to challenge Colorado Parks and Wildlife’s $4.5 million scheme are Colorado State University wildlife biologists who contend the proposed killing contradicts the agency’s own science. They accuse CPW officials of kowtowing to hunters who favor sacrificing lions and bears to increase deer-hunting opportunities.

“We find it surprising that CPW’s own research clearly indicates that the most likely limiting factors for mule deer are food limitation, habitat loss and human-induced disturbance – not predators,” CSU biologists Joel Berger, Kevin Crooks and Barry Noon wrote in a Saturday letter to CPW commissioners.

The biologists point to vast deer habitat in Colorado that has been fragmented by roads, damaged by oil and gas drilling and rendered inhospitable for wildlife by other development.

“We do not understand why compelling scientific findings based on research conducted in Colorado by CPW researchers is not being used to better inform management actions to benefit mule deer,” they wrote. “This seems both illogical and a waste of public funds. The scientific consensus is clear and compelling – predator control is a costly and ineffective management tool to increase mule deer populations.”

Colorado wildlife commissioners are scheduled to vote Wednesday on predator-control tests in the Arkansas River Basin near Salida and in the Piceance Basin near Rifle that would entail killing up to 15 more mountain lions and 25 more bears a year.

If the commissioners vote yes, state wildlife crews would use cage traps, culvert traps, foot snares and hunting dogs to immobilize mountain lions and bears. Those caught would be shot.

The state’s proposal says killings would carefully target bears and lions in areas where predators may be the primary problem for deer. Colorado’s deer population has fallen 110,000 short of the 560,000 deer that wildlife managers deem optimal.

CPW officials declined to comment on the CSU letter. They also declined to discuss their proposal. An agency spokeswoman referred to a 19-page Friday memo, sent by four agency researchers to wildlife commissioners, in response to a previous letter of opposition from scholars and scientists.

“CPW is well-aware of the importance of predators in ecological systems … and our track record demonstrates our appreciation for the value and role of these species (e.g., the reintroductions of Canada lynx and black-footed ferrets). We are proposing brief manipulations of thriving predator populations in order to gather valuable information for the future management of both predator and prey,” the memo says. “CPW recognizes the public’s interest in wildlife and its responsibility to manage wildlife for the use and enjoyment of all the people of this state and its visitors. CPW believes these research projects are entirely consistent with that responsibility. … CPW simply seeks additional information regarding the interaction of predator and prey species in Colorado, which it believes will be of value for consideration as part of future science-based management decisions.”

State wildlife officials this year did not oppose plans to allow up to 15,000 new oil and gas wells in the heart of critical deer habitat in northwestern Colorado, even though agency researchers have acknowledged oil and gas development hurts deer. A regional CPW manager recommended restricted winter activity. But national conservation and hunting groups did raise concerns about the impact on deer of those federal Bureau of Land Management oil and gas plans, which cover areas where lions and bears may be euthanized.

The Humane Society has led opposition to Colorado’s push for predator control.

“Colorado’s mountain lions and black bears are being threatened by the very agency we trust to protect these iconic native carnivores,” Humane Society state director Aubyn Royall said. “We want CPW to spend time and money on repairing mule deer habitat, addressing the primary cause of mule deer population decline — rather than spend millions on predator management.”

On Thursday, state commissioners received another letter of opposition from a coalition of wildlife conservation groups including the Cougar Fund, the Boulder Bear Coalition, the Center for Biological Diversity, the Endangered Species Coalition, the Audubon Society, WildEarth Guardians and the Sierra Club.

Faced with declining deer, CPW managers in recent years cut the number of deer hunting licenses they issue to fewer than 7,000 for the two areas where bears and lions would be killed. That’s down from more than 28,350 a decade ago.

CPW officials did not respond to questions about the revenue impact of dwindling deer.

The agency faces a fundamental problem because it relies heavily on revenues from fishing and hunting licenses to survive within state government, said CSU’s Noon, who with Crooks has collaborated with CPW researchers on past projects.

“CPW’s management objective should be to sustain all of the native wildlife species of Colorado. The species most at-risk are large-bodied mammalian predators,” Noon said. “I understand why CPW views their constituency as fishermen and hunters because most of their revenue comes from licenses. They should receive much more significant state funding. Today, they’re too dependent on the sale of licenses in order to carry out their operations. It’s something that should be taken up by the state legislature.”

Killing lions and bears to try to help deer is expected to alter the ecological balance across the 3,971 square miles where this predator control would be tested, but the killing probably would not have a significant statewide population impact.

Yet Colorado wildlife managers lack solid estimates for the statewide mountain lion and bear populations. They’ve said there is no way to know whether bear and lion numbers are increasing or decreasing because these animals are hard to count and surveys are costly. CPW officials have estimated Colorado has 17,000 bears, based mostly on extrapolations, with the lion population at around 4,500.

Hunters play a role, killing up to 1,364 bears and 467 mountain lions a year — more than in other Western states and twice as many as a decade ago. Colorado ranked third, behind Idaho and Montana, with hunters killing 3,414 mountain lions between 2005 and 2014.

If commissioners approve predator control after agency research in 2004 and 2009 found that predators are not the main problem, they could trigger a public backlash, Crooks said.

“It will lessen the credibility of our state wildlife agency if they’re pursuing actions that don’t have a strong scientific basis,” he said.