Moose in Interior Alaska: from 1,697-pound bulls to antlers that grow an inch a day

The largest bull ever recorded at a research station on Alaska's Kenai Peninsula weighed 1,697 pounds in November, antlers included, more than an average dairy cow. This National Park Service set of short facts covers moose in Interior Alaska's national parks, from their size and antlers to what they eat, how they handle cold and heat, and how they live through the rut.

A bull moose crossing the Kobuk River, Kobuk Valley National Park (NPS/Kyle Joly).

Size and antlers

Moose are the largest members of the deer family, and Alaska moose are the largest subspecies. Pairs of antlers from mature bulls average 45-50 pounds in Interior Alaska and the heaviest weigh up to 75. Mature bulls can grow about an inch of antler a day, adding about a pound daily. Females do not grow antlers.

A bull moose in Kobuk Valley National Park in the fall (NPS/Kyle Joly).

Eating

Moose eat shoots and leaves in summer and woody twigs in winter. The rumen, the first of their four stomachs, can weigh 90 pounds in summer and 112 pounds in winter. They prefer young woody vegetation such as willow, birch and aspen. Floodplains and areas burned about 15 years earlier, with their flush of regrowing shrubs, are generally considered the best habitat. In winter, moose spend only 6-8 hours a day actively foraging.

Droppings change with the diet. Summer scat is loose and resembles a dairy cow patty because moose are eating fresh growth. Winter scat is the familiar hard nuggets, mostly wood, since winter browse has so little nutrition. They have even been used as incense.

Cold and heat

Moose handle Alaska's winters well. Scientists have not found the temperature at which a moose starts spending energy to stay warm; moose have been tested down to -22°F and were not yet cold. They live where Alaska's coldest recorded temperature, -80°F, was measured along the Dalton Highway in 1971. But they overheat: they start panting to cool off above 28°F in winter and about 62°F in summer, because their coats differ by season, which is one reason moose are often seen standing in lakes on hot days.

Moving and shifting

Paths of two female moose tracked with GPS collars in a study in Gates of the Arctic (image from NPS's page).

Individuals differ. In a study that tracked two collared females in Gates of the Arctic, migratory and non-migratory moose moved roughly the same distance within a year, about 300 miles. The moose range is also shifting: its southern edge is moving north, likely because of warming temperatures and changing plant communities, and moose have spread farther north over the last 150 years, likely because shrubs have expanded across the arctic tundra.

Moose have a long history in Alaska. The earliest evidence of moose hunting there, about 13,000 years ago, comes from the Broken Mammoth archaeological site in the middle Tanana River valley, and moose have probably been hunted as long as people have lived in Alaska.

Two bull moose in Kobuk Valley National Park in the fall (NPS/Matt Cameron).

The rut

Males do not eat for about 2 weeks during the rut and can lose up to 20% of their body weight. They use their antlers to establish dominance by sparring, and at peak rut the sparring can turn deadly. The remains of two males permanently locked together by their antlers have been found, and many creeks around Alaska are named Antler Creek for that reason.

Twins and dewlaps

One common measure of moose habitat quality is the percentage of females that give birth to twins each year. Many twins in spring mean highly productive habitat; few twins may mean food limits and, if it is a new trend, a declining population. Triplets have been seen on rare occasions.

Both sexes have dewlaps, also called "bells," under the jaw, and young males often have the largest. Their exact function is a mystery. In other hoofed animals dewlaps have been linked with heat exchange.

Moose in winter along the Yukon River, Yukon-Charley Rivers National Preserve (NPS/Matt Cameron).

Sources

• National Park Service, "Moose: Did You Know?" (https://www.nps.gov/articles/moose-did-you-know.htm), Alaska public lands; photos credited in their captions to NPS; rewritten in hubnx's own words.