Moose are notoriously difficult to monitor and count accurately across the vast 3,472 square miles of Yellowstone National Park. Their solitary nature and preference for dense, remote habitats, such as thick willow bottoms and high-elevation spruce-fir forests, mean that a precise census is nearly impossible. This challenge forces wildlife biologists to rely on calculated estimates and indices to determine the status of the population.
The Current Population Estimate
Official park estimates indicate that the total number of moose residing within Yellowstone National Park is substantially lower than other large ungulates. The population is currently estimated to be fewer than 200 individuals park-wide. This low density is particularly noticeable when compared to the park’s massive elk population, which often numbers in the thousands.
The northern section of the park, known as the Northern Range, has seen its moose population decline to possibly fewer than 100 animals in recent years. This figure represents a significant reduction from historical counts, highlighting the species’ precarious status within the park boundaries. Because moose are sparsely distributed and inhabit areas with difficult visibility, researchers must use sophisticated methods to arrive at this population range.
Tracking and Survey Methodology
Park researchers employ a combination of traditional and contemporary techniques to monitor the secretive moose population and arrive at reliable trend estimates. Traditional approaches include aerial surveys, though their effectiveness is limited by the moose’s preference for dense forest cover. Instead of total counts, researchers often rely on indices, such as tracking the number of moose sighted per day during horseback or road surveys along established routes.
A contemporary approach involves non-invasive genetic sampling, utilizing fecal pellets collected from the snow during winter surveys. DNA is extracted from the pellet surface, allowing researchers to determine individual identity and gender. Furthermore, female pellet samples are analyzed for pregnancy hormone concentrations, providing valuable data on reproductive rates and overall population health. This non-invasive method is useful in rugged, remote terrain where capturing and collaring animals is challenging.
Historical Decline and Limiting Factors
The Yellowstone ecosystem supported an estimated 1,000 moose during the 1970s, a historical peak. This population flourished because decades of fire suppression allowed large, mature spruce-fir forests to develop, providing ample winter cover and browse. The decline began following the massive 1988 wildfires, which burned extensive tracts of the mature subalpine fir forests—the specialized winter habitat for the Shiras subspecies of moose. This loss of forage, combined with a harsh winter, resulted in high mortality.
Habitat changes continue to limit the population. Overgrazing by high numbers of elk and bison reduces the availability of willow and riparian browse in low-elevation areas. Competition for these woody browse species forces moose to rely heavily on conifer needles, a less nutritious winter diet that affects reproductive success. Warming climate trends also increase the risk of diseases and parasites, such as heavy tick infestations.
Predation by wolves and grizzly bears contributes to low calf survival rates. Grizzly bears are known to prey on young calves during their first few weeks of life. The combination of reduced winter forage, competition from other ungulates, and increased predation pressure maintains the moose population at its current low level.
Preferred Habitat and Range
Moose in Yellowstone occupy a specific ecological niche, preferring areas with abundant water and dense vegetation. They are strongly associated with riparian zones, including willow thickets along rivers and streams, where they forage heavily during the summer months. Their long legs allow them to navigate deep snow and access aquatic vegetation, a key component of their warm-weather diet.
In the winter, the moose relies heavily on mature, high-elevation stands of subalpine fir and Douglas-fir for both shelter and food. These conifer forests offer protection from deep snow, and the needles of these trees become their primary winter browse. Visitors are most likely to observe moose in the drainages of the park’s southwestern corner, along the Bechler and Falls rivers, and in the Soda Butte Creek, Pelican Creek, and Gallatin River areas. This limited range, tied to the availability of both willow bottoms and mature conifer forests, restricts the species’ overall distribution.