Large Mammals in Denali: How Many Are There?

Moose are increasing and are now quite common in Mount McKinley National Park Joseph Dixon, "Birds & Mammals of Mount McKinley National Park" (1938)

several moose standing on a sparsely-forested hilllside
Exact counts of wildlife aren't possible, but populations can be accurately estimated

Steve Thomas

With the exception of the road corridor and the area around park facilities, Denali National Park and Preserve is more than 9,000 square miles of wild terrain. That’s enough space for large animals to roam, rest, migrate, spar, sleep, avoid predators, browse, and do all the other things that large animals do in wild, unencumbered landscapes.

Innovative sampling techniques are used to estimate animal numbers, but the results are estimates of population sizes. Therefore it’s unrealistic to know exactly how many large mammals there are in Denali National Park and Preserve at any given time. Knowing about population trends, as well as about the quality and distribution of habitat for cover and food, is as important as knowing population sizes.

How To Estimate Populations

Aerial surveys are the primary means to estimate the size of large mammal populations. Imagine you’re the trained observer counting wildlife while the pilot flies the small fixed-wing plane over standard survey routes. You might track signals from radio-collared animals to locate non-collared ones in the same group. Knowing the number of animals per square mile from your survey, and how much of the park’s suitable habitat you covered, you can estimate the population size for the entire park.

Population sizes often are estimated separately on the north and south sides of the Alaska Range’s inhospitable spine of rock and ice. The timing of surveys makes a big difference in population estimates. Wildlife biologists working in the park provide these estimates of population sizes for Denali’s large mammals.

numerous sheet on a gravelly plain surrounded by steep mountains
A band of Dall sheep at an unusually low spot in the mountains

NPS Photo / Katie Thoresen

Grizzly Bears

On the north side of the Alaska Range, there are approximately 300 - 350 grizzly bears. This number is based on densities determined using radiocollaring of bears south and west of Wonder Lake (about 70 bears per 1,000 mi2 or 27 bears per 1,000 km2), then extrapolating to all grizzly bear habitat. On the south side of the Alaska Range, brown bear density is about 72 bears per 1,000 mi2 (28 bears per 1,000 km2). The density of grizzlies is likely to be higher south of the Alaska Range because the habitat includes more salmon streams.

Black Bears

Black bears have been observed throughout the park, particularly in forested areas. No formal surveys have been conducted north of the Alaska Range. The Alaska Department of Fish and Game (ADF&G) estimates that there are about 2700 black bears in Game Management Unit 16, or about 334 bears per 1,000 mi2 (131 bears per 1,000 km2). Based on the proportion of GMU 16B that is in Denali, there are about 200 black bears in the park on the south side.

Wolves

In April 2014, there were approximately 51 wolves in the 13 packs regularly being monitored by park biologists. The estimated density of wolves in Denali (about 7.4 wolves per 1,000 mi2 or 2.9 wolves per 1,000 km2) was lower than last year’s estimate of 8.2 wolves per 1,000 mi2 (3.2 wolves per 1,000 km2).

Caribou

The fall 2013 parkwide preliminary estimate for the Denali Caribou Herd was about 2,230 animals, the highest herd size since 1992. The estimated herd size was 1,960 in 2002, and 3,100 in 1990. Twenty-nine percent of calves born in 2013 survived to September. This population estimate reflects a slow growth of the Denali Herd at about 2 percent per year since 2003. Herd trend will depend largely on levels of calf recruitment into the adult population.

Moose

Moose surveys were conducted in November and December 2013 in two areas south of the Alaska Range where subsistence users harvest moose. Near Cantwell, 360 moose were observed in a 419-mi2 (1,085-km2) area. In the upper Yentna River valley (southwest Denali preserve), there were an estimated 179 moose in the 728-mi2 (1,885-km2) area. Moose density is typically low in the Yentna area. These areas in the southeastern and southwestern parts of Denali were last surveyed for moose in 2008. Moose numbers in the Cantwell and Yentna River areas appear to be stable or increasing slightly. The last survey on the north side of the Alaska Range was in 2011 and estimated 1,477 moose. New north side moose numbers will be estimated with a survey scheduled to be conducted in fall 2014.

Dall Sheep

In 2013, the estimate from ground-based surveys of lamb production was extremely low (3 lambs per 100 ewes). 2013 was the second year of low lamb production (in 2012, there were 10 lambs per 100 ewes). During 2008-2011, lambs production ranged from 29-40 per 100 ewes. The last aerial survey was in 2011, when wildlife biologists surveyed for Dall’s sheep between the Muldrow Glacier and the Nenana River using an aerial transect method developed for CAKN sheep monitoring. The estimated number of sheep north of the Alaska Range was 2,321 (with 1,867 for eastern areas). In 2008 - 2009, the estimate for the eastern areas (using a different method) was 1,724 sheep, suggesting that sheep numbers have remained fairly stable.

Other Challenges

Even estimates of population size are difficult to obtain. The challenges of estimating numbers of large mammals in the park include:

  • Births and deaths cause fluctuations in numbers.
  • Numbers may change as animals travel in and out of the park--what’s a park boundary to an animal?
  • Estimates made in one part of the park are extrapolated to other parts, assuming habitats are similar. There are limits to the accuracy of these assumptions.
  • Some population estimates are based on multi-year counts (each year in a different location), so estimates are ready only when counts are completed.
  • Sampling may be suspended when there is a lack of snow cover (to serve as a backdrop for seeing animals) or when aircraft are grounded by weather.

Conservation of large mammals in Denali Population estimates are an important part of the information needed to conserve populations of large mammals in Denali. Surveys are conducted frequently enough to estimate population sizes and identify population trends. But wildlife researchers also collect data on animal movements, productivity (number of young), health, survivorship, food preferences, and mate selection. Along with population trends, this information helps resource managers understand and manage these species in the park. The goal is to maintain the natural population dynamics of wildlife.