Moose Facts | Yellowstone Wildlife Guide

Moose are far less abundant than elk in the park, with an estimated population of fewer than 200. It is difficult to get an accurate count, however, since they have an uncanny ability to move their 1,000-pound bodies undetected through the brush and forest. Many hikers have been surprised by the sight of a moose. Moose are ornery and unpredictable, so it is best to keep as much space as possible between you and them!

Look for moose along the edges of waterways, browsing on the willows along the shore. With their long legs, they are well adapted to moving through water and deep snow.

PHYSICAL CHARACTERISTICS

The largest member of the deer family, the moose is a domineering force. Males weigh up to up to 1,000 pounds and females up to 900 pounds. They are much darker than elk and lack the elk’s characteristic rump.

Only males have antlers, which are dropped during the winter and regrown each year. The classic moose antler is a palmate shape with several tines. At 2 years old, almost all males have well-developed palms on their antlers, and the size of the palms, number of tines and antler spread continues to grow each year. Antlers reach their prime at 6 years of age, after which they begin to deteriorate, deforming and growing slightly smaller. Yearling bulls may have just a single spike or an antler with two spikes resembling a deer antler.

Typically, antlers are dropped in January and begin to regrow in April or May. During this growth period, the soft spongy antlers are covered with a dark brown, velvety skin that has blood vessels running through it.

FEEDING HABITS

The moose is a browser, whose Algonquian name (mus or moos) means “eater of twigs.” In the summer, an adult can consume 25 pounds of leaves, shrubs, twigs and other plant material per day. In the winter, they eat about half that amount. They are ruminants, which means they have a series of stomachs to help digest their woody diet. Their winter diet takes 20–30 percent longer to digest than their summer fare, which explains the lower food intake in the winter. A lack of winter foods limit moose populations.

From the spring to summer months, moose feed primarily on the new buds and fresh growths of willow, while aquatic plants such as the pond lily and duckweed round out their diet. Feeding in wetlands also gives them a quick escape route since their long legs allow them to go places where predators can’t follow.

During the winters, moose in Yellowstone rely on mature stands of Douglas fir and spruce trees for feeding. Climate change, which is resulting in longer, hotter summers, could contribute to more extreme fire events that will continue to suppress moose population numbers.

BREEDING

Many cows breed for the first time at one to one-and-a-half years of age and every year or two afterward. They are most productive between the ages of 4 and 12 but can continue to have calves until they are 20 years of age.

The peak of rut happens in September and October, with all females in an area going into estrus at the same time. Those who don’t mate will undergo a second estrus a few weeks later, leading to another rut.

Although moose are mostly solitary outside the rut, bulls will begin to create harems of 10 or more as fall approaches. Dominant males attempt to keep lesser bulls away from their harem, which can reach a size of 10 or more cows. Mating season is exhausting for these males, with frequent fights to protect the harem and constant surveillance to see which cows are coming into estrus, keeping them from eating for up to a month. By the end of the rut, a male moose might have lost 20 percent or more of his weight, which makes the impending winter much more foreboding.

Gestation lasts eight months, and calves begin to be born in May. They will nurse for approximately five months, gaining 2 to 4 pounds per day on the rich milk. The young will stay with the mother until the following year’s rut begins.

MOOSE POPULATION IN YELLOWSTONE

Moose have one of the highest reproduction rates of all the large, northern mammals. Despite this, the moose population in Yellowstone has decreased from approximately 1,000 in the 1970s to 200 in 2018. Most attribute this decline to the 1988 fire that destroyed the moose food source and caused many to die of starvation the following winter.

Know Before You Go