The spread of mountain pine beetles is slowing in Wyoming, according to a survey from the U.S. Forest Service.

Beetles killed 180,000 new acres of trees in 2012, but only 82,000 acres in 2013.

The Forest Service’s Aaron Voos says it’s not surprising.

“They’ve kind of eaten themselves out of house and home,” Voos said. “All of the trees that were susceptible to attack … have been either eaten and are now dead and dying, or they were able to fend off the epidemic and have developed some sort of resiliency.”

Pine beetle infestation has been slowing since the peak of the epidemic in 2009.

But spruce beetles are holding strong in Wyoming.