Last updated: July 17, 2026
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Moose Research in Rocky Mountain National Park
Since moose were relocated to the state of Colorado in the late 1970s, their populations have grown rapidly. Today, moose are present in every major drainage in Rocky Mountain National Park.
NPS Photo
Shiras moose (Alces alces shirasi) are large herbivores now present in Rocky Mountain National Park (RMNP). Shiras moose are the smallest of four subspecies of North American moose, with adult males (bulls) weighing up to 1000 pounds and females (cows) weighing up to 750 pounds.
Native or Not? Moose in RMNP
While historical accounts from the 1860s document one instance of a moose that was shot and killed near present-day Estes Park7, research has not revealed evidence of sustained breeding populations in Colorado3.
In 1978 and 1979, Colorado Division of Wildlife (now known as Colorado Parks and Wildlife (CPW)) released 12 moose each year into North Park, west of RMNP, to increase wildlife viewing and hunting opportunities. In 1980, the first moose was observed in the park, in the Kawuneeche Valley10. Until 2011-2012, moose in RMNP were rarely seen outside the Kawuneeche Valley and the west side of the park.
While there is ongoing academic discussion about whether moose are historically native to Colorado11 this debate does not directly impact how RMNP manages its species and ecosystems. Park managers are responsible for protecting and sustaining healthy ecosystems and wildlife populations—regardless of a species’ historical presence12. A good example of this management philosophy is the Elk and Vegetation Management Plan. This long-term effort aims to maintain a balance between elk populations and the health of vegetation communities on the east side of the park.
A Growing Population with Growing Concerns
Today, moose are present in all watersheds in RMNP, making them frequently observed on both the east and west sides of the park. In some instances, these typically solitary animals have been seen in unusually large herds in the summer in RMNP. While moose in other populations do occasionally congregate, this behavior tends to occur in winter when moose seek a break from deep snow8. These observations demonstrate that the park moose population is increasing, which aligns with statewide trends. From 2014 to 2025, CPW statewide population estimates jumped from ~2,400 to ~3,600 animals, representing a 51% increase in 10 years4.
Moose are wetland specialists, meaning they rely on the food and habitat found in wetland ecosystems and riparian corridors. During the summer months, moose predominantly forage on riparian willow which accounts for 91% of their diet5. Moose in the Kawuneeche Valley can eat up to 60 pounds of vegetation per day6.
The extirpation of wolves and grizzly bears from this region means moose in the park have few predators to regulate their population. This, paired with their willow-heavy diet, means that moose significantly impact already-degraded willow populations in the park.
During summer, willow makes up 91% of a moose’s diet compared to only 15% of an elk’s diet2. Because of these diet preference differences and the larger size of moose, each moose consumes about as much willow as 15 elk during a typical summer.
Willow are a focus for park managers because they are key components of willow-beaver wetland ecosystems. Willow is a critical food and dam building material for beaver, whose dams cause the overbank flooding necessary to create and maintain willow habitat and riparian wetland complexes. Healthy wetland ecosystems are biodiversity hotspots and provide ecosystem services such as improving water quality, buffering droughts and floods, and reducing spread of wildfire. RMNP is actively trying to restore willow wetlands at a landscape scale as part of the Elk and Vegetation Management Plan and the Kawuneeche Valley Restoration Collaborative (KVRC).
NPS Photo
Collaborative Research Addresses Important Management Questions
Research by park ecologists and partners helps further our understanding of the park moose population and its impact on willow communities and other vegetation, like subalpine fir. Two key questions asked by park biologists are:
- “How many moose are in the park?” and
- “How is this changing through time?”
In the past, this information was difficult to collect for moose in places like RMNP, because moose often spend time in dense vegetation where they are less visible to aerial or ground observers. This challenge was overcome using a new thermal infrared aerial survey method that was piloted in RMNP in 2019 and 2020. These aerial moose surveys provide counts of moose within a survey area and statistical models turn those counts into population estimates1.
Left image
An aerial image of a moose crossing a stream.
Credit: NPS Photo
Right image
An aerial, thermal infrared image of a bull moose near a river channel.
Credit: NPS Photo
Results from surveys of an area which covered roughly 65% of the park (268 miles2), estimated that moose density had increased 49% from 2020 to 2025. The 2025 survey, which covered nearly the entire park, estimated the total population at 240 moose1.
NPS
Aerial surveys and GPS collar data9 also help managers model how the park moose population might change over time. The ratio of bulls, cows, and calves identified during aerial surveys, paired with yearly survival data from collars, result in an estimate that the park moose population grew 5% annually in 2019 and 20201.
In addition, GPS collar data helps managers understand which habitat moose occupy. By pairing moose locations with vegetation height, distance from water, slope, and other environmental characteristics, researchers can better predict habitat preference and use this information to identify areas of the park where moose are more likely to establish home ranges.
Aerial thermal infrared surveys are used to estimate the moose population in RMNP. Moose density in the park increased 49% from 2020 to 20251.
GPS collar data also captures how moose move around and utilize the habitat they occupy. Pairing this space-use data with population data can help researchers estimate the cumulative impact moose are having on park willow populations. Vegetation surveys conducted as part of the EVMP document browse impacts by both moose and elk and help monitor willow and other vegetation conditions on the ground.
NPS Animation. Map data ©2022 Google.
Knowledge and data from moose research will help inform current vegetation management plans and will support potential moose management strategies in the future.
NPS Photo
Resources and References
1. Deacy, W.W., and H.G. Abouelezz (2026) Moose Distribution and Abundance in Rocky Mountain National Park: 2025 Inventory Results. Science Report NPS/SR—2026/428. National Park Service, Fort Collins, Colorado. https://doi.org/10.36967/23036442. Baker, D. L., and Hobbs, N. T. (1982) Composition and Quality of Elk Summer Diets in Colorado, The Journal of Wildlife Management 46 (3), 694-703.
3. Brunswig, R. (2015) Archaeological and Paleontological Evidence for the Prehistoric and Early Historic Presence of Bison (Bison sp.) and Moose (Alces alces) in Rocky Mountain National Park and the North Central Colorado Rocky Mountains. Internal Report.
4. Colorado Parks and Wildlife. Moose Statistics. Retrieved 2026, from www.cpw.state.co.us.
5. Dungan, J. D., and Wright, R. G. (2005) Summer diet composition of Moose in Rocky Mountain National Park, Colorado, Alces 41, 139-146.
6. Dungan, J. D., Shipley, L. A., and Wright, R. G. (2010) Activity patterns, foraging ecology, and summer range carrying capacity of moose (alces alces shirasi) in Rocky Mountain National Park, Colorado, Alces 46, 71-87.
7. Estes, M. (1939). Memoirs of Estes Park. The Colorado Magazine, 16(4), 121-132. https://www.historycolorado.org/sites/default/files/media/document/2018/ColoradoMagazine_v16n4_July1939.pdf
8. Peek, J. M., LeResche, R.E., and Stevens, D.R. (1974) “Dynamics of Moose Aggregations in Alaska, Minnesota, and Montana.” Journal of Mammalogy 55 (1): 126–37. https://doi.org/10.2307/1379262.
9. Rocky Mountain National Park (2017). Moose Annual Survival, Population Estimation, Habitat Use and Carrying Capacity on the Summer Range in Rocky Mountain National Park. Fact Sheet.
10. Stevens, D.R. (1988) Moose in Rocky Mountain National Park. Internal Report.
11. Taylor, W. T. T., J. A. F. Wendt, J. Dombrosky, et al. (2026) Understanding Ancient Moose Populations in the Southern Rocky Mountains. Journal of Biogeography 53 e70279. https://doi.org/10.1111/jbi.70279.
12. National Park Service. 2006. Management Policies 2006. Washington, DC: U.S. Department of the Interior, National Park Service. https://www.nps.gov/subjects/policy/upload/MP_2006_amended.pdf