What Moose Eat in Summer at Rocky Mountain National Park

A moose in Rocky Mountain National Park. NPS.

How moose got here

Moose were not native residents of Rocky Mountain National Park. The Colorado Division of Wildlife released twelve moose (Alces alces shirasi) near Rand, Colorado, west of the park, in 1978–1979. They bred and spread; the first moose was seen in the park in 1980. Park staff now estimate 61–66 moose spend the summer there, some year-round.

Why diet matters

Moose change their habitat — the mix and structure of plant communities. The park already has a large elk population, and managers worry about the combined browsing of elk and moose on willows, and the knock-on effects on animals such as beaver. Summer — when moose build fat for winter and share range with elk — is the key season.

The study

In the summers of 2003 and 2004, J.D. Dungan, a graduate student at the University of Idaho, studied moose on the park's west side, in the Colorado River drainage, two ways:

• watching moose feed — 11 females and 43 males;
• fecal analysis: a laboratory counted plant fragments in fresh pellets under a microscope to measure the diet's make-up.

The methods complement each other: pellets usually identify plants only to genus, while observation cannot measure amounts.

Results

Moose ate 20 kinds of plants over the summer, most of all willows.

• Other woody plants: alder, quaking aspen and bog birch.
• Moose were also seen eating aquatic plants, forbs (broad-leaved herbs such as dandelion) and grasses.
• Diet was most varied in July, with 18 plants eaten.
• In summer, moose use streamside willow communities, which hold only small areas of aquatic plants or forbs.

The park planned winter moose surveys to complement the summer study.

Sources

Based on "Moose Summer Diet," by Bert Cushing, Rocky Mountain National Park, National Park Service; a work of the United States government in the public domain. The summary is not a statement of park policy. The article's photographs are copyrighted by their photographer and are replaced here by an NPS photograph.