DENVER — Experts from the Humane Society of the United States are in Denver to speak out against a proposal to kill what they call “significant numbers” of mountain lions and black bears.

Colorado Parks and Wildlife held a listening session on Monday evening about the proposal to kill native carnivores in certain areas to study mule deer populations.

The proposal involves killing mountain lions and black bears in the Piceance Basin near Rifle and Upper Arkansas River near Salida.

“CPW is currently developing proposals to examine the role of predation in limiting mule deer numbers,” the CPW website said.

Mule deer populations began to decline across the western United States in the 1990s, according to CPW.

There were around 600,000 deer in the state in 2006. That number dropped to about 390,000 in 2003. CPW’s population objective for mule deer is approximately 560,000 statewide.

“We don’t necessarily want to wait until there’s such a decline we have an impossible time bouncing back. We want to make sure we’re proactive,” Colorado Parks and Wildlife spokeswoman Jennifer Churchill said.

“Researchers recognized both habitat quality and predation as possible factors, but did not know which one played a larger role in mule deer population declines,” officials said.

Officials also cited barriers to migration, competition with elk, disease, doe harvest and hunting demands, highway mortality, recreation impacts and weather.

If approved, upward of 50 percent of all mountain lions would be killed in the study area ranging from Leadville to Canon City. In the study area near Rifle, as many as 15 mountain lions and 25 black bears would be killed every year.

In a statement released by the Humane Society, officials blamed “heavy fossil fuel extraction and housing development in the region” for limiting mule deer populations.

CPW is studying the effects of energy development on mule deer behavior and population trends in the Piceance Basin.

Critics of the study claim it is “unnecessary and redundant,” and killing the mountain lions and black bears will result in the “orphaning of kittens and cubs, who will die from dehydration, starvation or predation.”

The Humane Society also argues lions and bears aren’t to blame for the declining deer numbers in the state.

“They don’t target large numbers of mule deer. They target the unhealthy, the sick ones that are going to die anyway. This is playing with wildfire. These studies are a waste of time,” said Haley Stewart with the Humane Society.

Colorado Parks and Wildlife will vote on the proposal in December. If approved, the studies would begin this winter.