Field Notes
U.S. Fish & Wildlife Service
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ALASKA REFUGES: Changing Climate Requires New Moose Survey Methods
Alaska Region, January 6, 2016
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A group of moose observed during an aerial survey, Togiak National Wildlife Refuge, Alaska. Brown moose on snow are easily detected.
A group of moose observed during an aerial survey, Togiak National Wildlife Refuge, Alaska. Brown moose on snow are easily detected. - Photo Credit: Andy Aderman/FWS
Poor snow conditions have made detecting moose from the air more difficult.
Poor snow conditions have made detecting moose from the air more difficult. - Photo Credit: Pat Walsh/FWS

Moose on the Bering Sea? Really? Well, maybe not quite, but moose have recently colonized areas of western Alaska where they had never previously been observed. This development, along with a changing climate, presents new opportunities and challenges.


Moose numbers have increased in and around Togiak National Wildlife Refuge (NWR) from less than 10 moose observed during surveys in the early 1980s, to over 1,600 moose in 2011. For years, biologists have been able to estimate the number of moose by conducting low-level aerial surveys during the winter. This method has worked well because, historically, the refuge was completely snow-covered during surveys, and moose could be easily seen against the white background. In recent years, however, snowfall has decreased and moose cannot be reliably detected: brown moose on a brown landscape are difficult to spot from the air. Scientists are predicting less snowfall in this region over the long term as a result of changing climate. If you cannot see the moose, then you cannot count them. If you do not know how many exist, then it is really hard to make decisions about hunting seasons.

The changing snow conditions throughout Alaska have been the impetus for discussions among biologists, managers, and statisticians about methods that can improve our ability to manage moose populations. At Togiak NWR, we are testing our ability to account for changing conditions by building “sightability models”, using radio collared moose. These models are useful for two reasons. First, we can estimate the proportion of the population that was not detected during the survey and correct potential bias in the estimate of the total number of moose. Second, we are hoping to use the models to predict the proportion of the population undetected on future surveys and hopefully at other locations by accounting for factors such as snow conditions, habitat types, and differences in observers. How well these models perform will be partially dependent on the number trials conducted, so we are collaborating with other partners.

Statisticians and wildlife biologists from the U.S. Fish and Wildlife Service, Alaska Department of Fish and Game, and University of Alaska Fairbanks are working together to improve their abilities to estimate moose abundances throughout Alaska. Developing collaborative solutions to monitoring moose population in Alaska is the topic of an upcoming workshop during the Alaska Chapter of the Wildlife Society that will bring together wildlife biologists, biometricians, and managers to discuss how to improve moose management. The goals of this workshop are to better understand what statistical methods are being used to estimate moose abundances across Alaska, identify opportunities for improving the logistics and statistics behind estimating moose populations in Alaska, and facilitate future collaboration between agencies. When agencies work together, they can save money and time!

Moose are an important subsistence resource and have been shown to play a central ecological role. Therefore, estimates of their abundances are critical for making science-based management decisions. Estimating moose abundances in novel habitats like western Alaska presents challenges and opportunities but collaborations between regional biometricians, refuge biologists, and other agencies can address these challenges and lead to improved management.

For more information on this work, contact Refuge Biometrician Anna-Marie Benson (907-456-0386) or Togiak Refuge Supervisory Biologist Pat Walsh (907-842-8402).

Contact Info: McCrea Cobb, 907-786-3403, mccrea_cobb@fws.gov
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