The largest member of the deer family, the moose, is a fixture in the Greater Yellowstone area. The subspecies found here is the smallest of the five moose subspecies and exists at the farthest southern end of their natural range. These moose have adapted to the region’s diverse habitats, ranging from dense forests to wetlands to mixed sagebrush-bitterbrush shrubland. Despite their smaller size compared to other subspecies, Shaira’s moose are an important and successful part of the local ecosystem. They serve as prey for predators like wolves and bears while also influencing vegetation patterns through their browsing. Visitors to the area have a good chance of spotting these iconic animals, especially during dawn and dusk when they are most active. Spectacularly, the moose in southern Grand Teton National Park are known to form dense all-male aggregations starting shortly after their October rut, and are easily viewed while browsing in North America’s largest alluvial fan, Ditch Creek.
Size: Up to 1,200 lbs
Shaira’s moose are the smallest of the four subspecies of moose in North America. This size adaptation increases their surface area to volume ratio, enabling them to dissipate heat more efficiently. As a result, they are well-suited to survive in the relatively mild temperatures found in the southern latitudes they inhabit. This contrasts with larger moose subspecies in colder regions, where a lower surface area to volume ratio helps conserve heat.
Diet
Moose are specialized browsers, meaning they eat a diet of only woody plants. Their preferred foods vary seasonally and by region, but in the GYE, their diet consists primarily of deciduous shrubs and small trees. Including: willow, chokecherry, serviceberry, young aspen, cottonwood, and, during seasons of low snow and cool temperatures (autumn and late spring), antelope bitterbrush.
Breeding:
Moose are isolationist breeders. Males will compete with other males for the right to breed a female who comes into estrus for only 36 hours each year. Once a male has wooed a female and fended off rivals, he follows the female closely, attempting to corral her away from would-be suiters. After 24-36 hours, he moves on to the next female. Females will breed each year from the time they are 1.5 years old until around 12-14 years of life when their body condition causes them to alternate years. Moose do not go through menopause and will continue to breed until their death, around 16 years old, in the wild.
Population:
Moose populations are inherently variable and subject to fluctuations over time. In Jackson Hole, current estimates indicate around 350 moose, a significant decline from the peak of nearly 1,300 in the late 1980s. This pattern of population boom and bust is common across the Greater Yellowstone Ecosystem (GYE) and is characteristic of moose populations throughout their range due to their colonizing nature.
Historically, moose were uncommon in the Yellowstone region during the 1800s. Their numbers gradually increased after the establishment of protected national parks, which provided a safer habitat free from unregulated hunting. However, over the past three decades, moose numbers have trended downward. This decline is complex and driven by multiple factors, including climate change, increased parasite burdens, and predation pressures.
The impact of climate change affects moose both directly, by altering habitat and food availability, and indirectly, by increasing parasite survival rates and extending periods of vulnerability. Parasites such as winter ticks sap energy and can cause significant mortality, particularly in subadult moose. Predation from wolves and especially bears also influences population dynamics.
Despite these challenges, moose populations have demonstrated resilience historically. Given sufficient time and favorable environmental conditions, it is likely that the Jackson Hole moose population, like others across North America, will eventually recover. This natural ebb and flow is part of the ecological balance in their habitats.
