Exponential growth of moose population in Rocky Mountain National Park challenges officials
Moose are a fundamental part of living in Colorado’s High Country, but an ever expanding population of the large animals poses unique challenges that officials from Rocky Mountain National Park hope to illuminate with a newly implemented research project.
Historically, there is a significant disagreement regarding whether or not moose are native to Colorado.
Officials from Colorado Parks and Wildlife note that records dating back to the 1850s indicate small numbers of transient moose, typically single bulls, were sited or hunted in Colorado, but no stable breeding populations were ever established in the state until 1978.
The same is true for Rocky Mountain National Park.
According to park officials, the park’s fossil records includes sparse evidence of moose. A single moose was harvested in Moraine Park around the time the park was first established. From that time until 1980, there were no recorded moose sightings in the park.
The park’s 1980 moose sighting came just two years after state wildlife officials transplanted 24 male and female moose into North Park. Since 1980 moose have been sighted in Rocky’s Kawuneeche Valley on a regular basis. Around 10 years ago, however, visitors began reporting sightings of moose on the park’s eastern slope near Estes Park, though incidents remained few and far between until roughly five years ago.
Over the last five years, moose populations have grown exponentially. Park officials monitor 254 separate vegetation plots within the park gathering a variety of data. In 2013, only 3 percent of vegetation plots on the park’s east side showed signs of moose, typically in the form of droppings. In 2018, 85 percent of vegetation plots on the east side showed signs of moose presence.
On the west side of the park, where moose populations have been established for decades, 80 percent of vegetation plots showed moose presence in 2013. According to park officials, every single vegetation plot on the park’s west side showed signs of moose presence in 2018.
Moose have a significant impact on the ecosystems they inhabit especially on the willow thickets and aspen stands that they feed upon. According to Rocky Mountain National Park Landscape Ecologist Hanem Abouelezz, moose eat approximately 50 to 60 pounds of vegetation each day during their annual growing season in warmer months.
According to Abouelezz, the park has seen a 40 percent reduction in willows in the last 20 years, though she noted that reduction is due to many factors including moose and elk grazing and a fungus spread by birds that feed on willow sap. But that reduction in willows, coupled with anecdotal signs that the moose population in the park continues to grow, were catalyzing factors for federal officials who decided to initiate the park’s new moose research project.
The research project will continue for the next five years and is expected to wrap up in 2022. The project is entirely focused on gathering data park officials can call upon when making future management decisions regarding moose in the park. The project was initiated last summer when park officials collared six moose on Rocky’s west side. This year park officials have collared an additional 21 moose between the park’s east and west sides. They plan to collar a total of 40 moose; 20 from each side of the park. The collaring work is expected to wrap up next summer.
Abouelezz primarily handles the collaring process with assistance from other park staff. Unlike other collaring efforts, which sometimes are handled through aerial darting, Rocky’s current collaring efforts are being done entirely from the ground. Once a moose is selected Abouelezz moves on foot to the moose’ location. The moose is shot with a sedative using a dart gun.
After approximately 10 minutes the moose becomes unconscious. Abouelezz then begins a roughly 45 minute process where a GPS collar is attached to the animal and additional samples, such as blood and rectum biopsies, are taken. A sedative reversing agent is administered and roughly 10 minutes later the animal is back up and eating. The collaring efforts are focused on adult animals two years or older. Rocky is collaring a roughly even mix of bulls and cows for their research.
Abouelezz noted the collars themselves, which are placed around the neck of the moose, are designed to expand or shrink as the moose grow and will separate if they become caught on tree limbs or other snags. The collars gather location data only and while some data sets are gathered early, due to mortality or collars falling off, park officials do not expect to have the majority of the data until 2022 when they look to remove the collars.