Biological Projects

Moose Population Monitoring:

Population identity and movements of moose in the Togiak, Kulukak, and Goodnews River drainages, southwest Alaska

Moose are relative newcomers to southwest Alaska and have recently established themselves in the eastern half of the Togiak National Wildlife Refuge. In the Togiak River drainage, aerial surveys conducted during the 1980's and early 1990's documented very few moose. Subsequent surveys revealed an increase from 84 moose in 1994 to 652 moose in 2002.

Because little was known regarding movements, immigration and population parameters of moose in the Togiak Refuge, a cooperative study with the Alaska Department of Fish & Game (ADF&G) was initiated in 1998 to address these and other factors.

In late March and early April 1998, Togiak Refuge and ADF&G biologists radio collared 36 moose (27 cows and 9 bulls) within Togiak Refuge. Since then, additional cows and female calves have been radio collared. All moose are aerially radio tracked monthly, and cows are tracked weekly during calving (mid-May to mid-June). Upon locating a collared moose, the biologist records the location, habitat type, activity of the animal, and association with other moose.

Biologists usually express population statistics as ratios per 100 cows. These ratios are based on information obtained from observation of radio collared moose, which are assumed to be representative of the population at large. For example, if 18 calves are observed with the 27 radio collared cows, the calf ratio would be expressed as 67 calves per 100 cows. Moose often have twin calves, so it would be quite possible to observe 32 calves with the 27 cows, yielding a calf ratio of 118 calves per 100 cows.

Calf production has averaged 136 calves per 100 cows. Fifty-three percent of calves, on average, survived until fall, yielding an average recruitment of 71 calves per 100 cows. Annual adult mortality has averaged 14.4 percent. Predation by brown bears is the leading cause of mortality, followed by illegal harvest. Other sources of mortality include legal harvest and fighting (locked antlers).

Annual home range size for both cows and bulls averaged 132 mi², and ranged from as small as 4 mi² up to as big as 472 mi². Preliminary research indicates the Togiak River drainage contains 560 mi² of optimal moose winter habitat and an additional 520 mi² of secondary winter habitat. The carrying capacity is estimated to be 1,100 to 1,750 moose.

As moose have now become established in the Togiak River drainage, expansion into unoccupied habitats in other areas of Togiak Refuge is likely. Togiak Refuge staff continue to collect information on moose and their habitats to maintain a healthy population for the continuing benefit of the American people.