Officials are worried that the burgeoning moose population in Rocky Mountain National Park is hurting the park’s natural ecosystem – specifically wetlands and willows – that other wildlife depend upon.

“We know we have heavily degraded wetlands and a long history of too many elk on the winter range on the east side of the park that is reducing willows,” said Will Deacy, the park’s large mammal ecologist. “We strongly suspect moose are exacerbating that, which is making restoration of our wetlands difficult.”

While moose were once scarce within the park, today, that’s not the case. “There are now many more moose sightings on the east side of the park, and moose are in every drainage in the park,” said park spokesperson Kyle Patterson.

According to Deacy, about 4% of the park is comprised of wetlands (and willows), and 95% of the willows on the west side have died out over the last 20 to 30 years. In the summer, willows make up about 91% of a moose’s diet with a large moose able to consume about 45 pounds or more. In comparison, while willows make up about 15% of an elk’s diet, that only equals about 3 pounds of willows per day. 

Park officials say that moose populations have grown 5% annually in 2019 and 2020 with roughly 145 moose roaming the area, according to the Coloradoan. However, that number only accounts for about 65% of the park and didn’t include known moose habitat in the Wild Basin and Paradise Park areas, meaning that the number is likely low and the number of moose in Rocky Mountain National Park is underestimated. 

They plan to conduct an aerial moose population survey later this summer.

Moose were introduced to Colorado in the late 1970s when Colorado Parks and Wildlife (CPW) brought 24 moose from Utah and Wyoming, according to the Coloradoan. Since then, the population has grown to about 3,500 animals. CPW has worked hard to keep moose populations in check outside of the park, using hunting as their main tool.

In fact, hunters killed 473 moose statewide in 2023, with an overall 77% success rate.

“It’s important to use hunting, especially harvesting cows (females), so we don't damage the willows and aspen,” said Andy Holland, CPW’s statewide big game manager. “Moose will go gangbusters, rapidly increasing. We want to keep them at objective numbers so they don’t exhaust the resource and crash. Nobody wants that.”

Managing expanding moose populations is only one part to restoring the park’s wetlands and willow ecosystem to a sustainable level.

“The perfect ecosystem has a bunch of connected parts,” said Deacy. “Restoration can’t mess with just one part. There are three to four major parts to it.”

Managing moose, elk, and deer to population levels that allow for the growth of willows is necessary to allow for wetland restoration – difficult because of the fact that hunting isn’t allowed in the park and there are few natural predators there, as well, resulting in high survival rates – and population growth – within park ungulates. And it also takes the help of other wildlife.

“The cheat code is if we can restore the processes for the beavers, that will improve the hydrology and tall willow growth,” said Deacy. “A really healthy ecosystem is 100% consistent with excellent wildlife viewing.”