Rocky Mountain moose: Past, present and future — Part I

Estes Park is celebrating its elk this weekend, but another enormous ungulate is increasingly stealing some of the spotlight.

Moose have become a familiar sight in and around the eastern side of Rocky Mountain National Park, where visitors and locals delight in spotting — and photographing — them at Sheep Lakes, Sprague Lake and in the Endovalley area, often with their heads buried in stands of willow.

Their growing presence, however, raises a complex question for Rocky Mountain National Park: How many moose can the park’s wetland and riparian ecosystems support?

While visitors and wildlife photographers celebrate sightings of the animals, biologists are concerned about the effect a growing moose population could have on willows, wetlands and the other species that depend on those habitats.

And behind that management challenge lies an even more fundamental and surprisingly contentious question: Do moose belong here?

A study published earlier this summer, “Understanding Ancient Moose Populations in the Southern Rocky Mountains,” by researchers from the University of Colorado Boulder, New Mexico State University, University of Utah, Crow Canyon Archaeological Center, History Colorado and the University of Cincinnati may shift that discussion from whether moose belong in Colorado to a more nuanced question: How long have they been here, and in what numbers?

Since Rocky Mountain National Park was established in 1915, scientists have studied its wildlife and ecosystems to help guide decisions intended to protect the park’s natural resources for future generations. Today, the expanding moose population presents park managers with another complicated wildlife-management challenge.

Historical and archaeological evidence indicates moose were present in the region long before modern wildlife managers brought them to Colorado. But whether they historically maintained substantial, self-sustaining breeding populations here is a matter of debate.

Moose largely disappeared from Colorado by the middle of the 20th century. There were occasional sightings during the first half of the century, and newspaper accounts, photographs and diaries suggest sightings increased from the 1940s through the 1960s.

“Reintroduced”

In 1978, the Colorado Division of Wildlife, now Colorado Parks and Wildlife, began a program to establish a breeding population of moose in the state, both for hunting and wildlife viewing.

The agency initially transported 24 male and female Shiras moose (Alces alces shirasi) from Wyoming and Utah to the North Park area near Walden in northwestern Colorado.

The animals thrived.

Walden became so closely associated with the species that the Colorado General Assembly designated it the state’s “Moose Viewing Capital” in 1995.

Over nearly five decades, Colorado wildlife officials conducted five separate transplant operations involving 259 moose. Some animals came from outside Colorado, while others were moved from established populations within the state.

Today, Colorado has more than 3,600 moose, and their range continues to expand.

Moose have recently turned up well outside areas where Coloradans once expected to find them. Animals have been reported north of Denver in Arvada and on the eastern plains near Nunn and Greeley. Moose have even wandered south into New Mexico, with sightings around Taos and Santa Fe in recent years.

The Estes Valley is seeing that expansion firsthand.

Last spring, a bicyclist spotted a young moose grazing in a marshy area along Fish Hatchery Road on property where the Town of Estes Park has proposed building workforce housing. A year ago, golfers reported seeing two moose checking out the 18-hole Estes Park Golf Course along Fish Creek Road.

Inside Rocky Mountain National Park, moose watching has become an attraction of its own.

Throughout the summer, visitors stake out lakes, willow thickets and marshy areas hoping for photographs. One enormous bull, affectionately nicknamed “Frank the Tank” by photographers, has developed something of a following. Twin calves born last year delighted visitors fortunate enough to see them with their mother.

Moving east

Moose have long been more numerous on the western side of Rocky Mountain National Park, particularly in the Kawuneeche Valley near Grand Lake. But they have been steadily expanding east across the Continental Divide.

Their abundance on the west side has become part of a much larger ecological challenge.

For the past six years, the Kawuneeche Valley Restoration Collaborative has worked to restore wetlands and riparian habitat in the valley. Partners include Rocky Mountain National Park, The Nature Conservancy, Colorado River District, Grand County, Town of Grand Lake, U.S. Forest Service, Northern Water, and Colorado State University.

Studying moose, however, is not easy.

Unlike elk and deer, moose often remain under the cover of trees and dense vegetation, making them difficult to count from the ground. Rocky Mountain National Park uses aerial surveys to estimate populations, track distribution, and monitor changes over time.

Park biologists have estimated a density of about 0.21 moose per square kilometer within Rocky Mountain National Park.

Those surveys can also help scientists understand what moose are doing to the landscape.

Big animals with big appetites

An adult moose is an eating machine. Moose browse heavily on willows and aspens and also eat aquatic vegetation. Willows can make up much of their diet in Rocky Mountain National Park’s wetland and riparian areas. An adult moose can consume roughly 40 to 60 pounds of vegetation a day.

That appetite matters.

Heavy browsing can prevent willows from growing tall enough to reproduce successfully and can change the structure of wetland habitat. Those changes can ripple through an ecosystem, affecting birds, beavers and other wildlife that depend on healthy willow communities.

The National Park Service has identified moose browsing as one of the pressures contributing to the degradation of wetland and riparian areas in the park.

That raises a difficult management question: Are there enough willows and other plants to sustain a growing moose population without fundamentally changing the ecosystem?

Even asking the question can be controversial.

Some naturalists point to archaeological evidence suggesting moose were present in the southern Rocky Mountains thousands of years ago and argue that describing the animals simply as nonnative ignores that history.

Other researchers distinguish between the occasional historical presence of moose and evidence of a large, persistent breeding population. Under that interpretation, the animals may have wandered through Colorado for centuries or millennia without existing in anything like the numbers seen today.

That distinction matters because wildlife managers must decide what population — and what landscape — they are trying to preserve.

Coming in Part 2: What scientists are learning about the history of moose in the Rocky Mountains, how researchers are studying their impact on Rocky Mountain National Park, and what the growing population could mean for the park’s future.