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Alaska's moose management: Science or comic-book biology?

Stephen F. Stringham, Ph.D.
Terry Julien photo

Alaska’s Board of Game (BOG) claims that its aim is to keep each moose population at carrying capacity so as to maximize sustainable yield.  However, those two targets are mutually exclusive.  This principle applies whether the animals being managed are ungulates or fish.  Anyone doubting that you can’t have your cake and eat it too can test the principle by cramming as many trout fingerlings as possible into a pond, then seeing how many survive until large enough to harvest.

If the BOG listened to Alaska Department of Fish and Game (ADF&G) biologists, they would know that a population near carrying capacity (CC) has so much competition for food that a substantial portion of the population is malnourished. Animals tend to be relatively small in body size, with poor health and high vulnerability to parasites, disease, severe weather, and predators. They produce few young.  Natural mortality rates are high for all age-sex classes.  Hence, such populations have a sustainable yield (harvestable surplus) no higher than that of a small population.  Figure 1 below illustrates this for population densities whose sustainable yield is half of maximum.

Surplus is maximized at an intermediate density where there is enough food per capita that most animals have high rates of reproduction and survival due to relatively large body sizes, good health, and high resistance to parasites, disease, weather, and predators.  This is known as optimum density.  The ADF&G) has not publicized optimum densities for Alaska's moose populations.  But estimates for other large mammals are commonly in the neighborhood of 50 to 70 percent (+/- 10 percent) of carrying capacity. But whatever the figure for Alaskan moose, shouldn’t optimum density, rather than maximum density, be the goal of ungulate management?  Indeed, why isn’t it?

Figure 1: Sustainable yield relative to population density (conceptual model)

Figure 1: Sustainable yield relative to population density (conceptual model). The vertical axis is sustainable yield (harvestable surplus), expressed as percentages of the maximum sustainable yield possible under those habitat conditions. The horizontal axis is expressed in percentages of carrying capacity. Both sustainable yield and carrying capacity can be measured in terms of moose per 1000 sq. mi. The shaft of each vertical arrow marks one population density. The point of that arrow represents size of the sustainable yield at that density.  OD = Optimum Density.

Populations at optimum density not only produce more moose for hunters to harvest, they also tend to be more resistant to rapid declines in carrying capacity.  This is especially obvious where CC is governed by food supply – not just by the amount of food that grows, but by the amount that moose can reach and browse profitably.  Profit means that they gain more in nutrients and energy from their food than it costs them to get the food.  Moose can normally browse profitably during spring through fall.  But during winter, the energy gained from food can be less than the energetic costs of  (A) wading through snow to reach browse, (B) eating snow for moisture to digest the browse, then (C) warming browse and snow up to body temperature.  Hence, carrying capacity is largely governed by the amount of food that moose can profitably browse during winter (and sometimes by access to drinking water). 

Populations at carrying capacity live on the brink of disaster because any sudden drop in food supply can further reduce nutritional status for much of the population, leading to widespread debilitation and perhaps starvation.  That’s what happens during severe winters when deep snows keep moose from reaching enough food to sustain themselves. This is shown in Figure 2 for an imaginary case where CC declines by 40 percent.

With these biological principles in mind, one might well ask why the BOG’s widely advertised goal is keeping moose populations as close as possible to carrying capacity – where sustainable yield is low and vulnerability to drops in carrying capacity are high.  Do they know something about moose management that professionals don’t?  Has the BOG been guided by ADF&G scientists or by comic-book biologists who see everything in terms of villains and superheroes -- in this case, villains with long sharp fangs and shaggy fur, hunted by heroes who fly only with the aid of aircraft, while wearing camo instead of capes.

Even if our only management goal was maximizing harvestable yield of moose, predator control would be warranted only where necessary to keep population density from falling far below optimum density.  Populations near carrying capacity might be suffering from too little harvest rather than too much.  If hunters aren’t doing the job, predators must -- or winter, starvation, disease and parasites eventually will.

Fig. 2: Sudden drop in winter carrying capacity affects sustainable yield

Figure 2:  Effect of a sudden drop in winter carrying capacity on sustainable yield. In this imaginary example, carrying capacity has dropped to 60 percent of its previous level. Population density has dropped even more.

Assuming that all predation harms a moose population, and that every moose eaten by a predator is one less for us to eat, is the kind of comic-book biology that may be inevitable when special interest groups and their political cronies insist on controlling how wildlife are managed, rather than just recommending the goals of management and leaving methods to the pros.

For years now, political pressures have kept ADF&G from releasing much information on any aspect of predator-prey management except statistics (of questionable credibility) on estimated numbers of ungulates eaten by wolves and bears.  The public hasn’t been privy to information on carrying capacity, optimum density, and food supplies for moose as these are affected by habitat succession, moose density, food competition from snowshoe hares, wolf predation on hares, and enrichment of protein levels in browse plants through fertilization by the dung of wolves and bears which have been eating salmon.  It’s time that this information was made public, and that both ADF&G and the BOG explained how each organization interprets such data, step by logical step, for predicting how moose and caribou populations respond to variations in wolf and bear numbers.  I suspect that ADF&G’s results don’t match the BOG’s. Wildlife management isn’t exempt from the need for governmental transparency and accountability.

Restoring Credibility in Game Management

No agency or governing board willingly submits its decisions to outside critique.  However, that is exactly the step needed to restore credibility to Alaska’s predator-prey management.  ADF&G data and BOG interpretations should be explained to the public and then evaluated by a team of other experts.  Proponents and opponents of intensive predator control should have equal influence on selection of these experts.  They should be able to choose biologists currently or previously employed by ADF&G or other government agencies, universities, businesses or NGOs who can contribute additional insights, for instance, based on research in other regions or on other species.  The team should also include highly experienced wildlife observers (e.g., hunters and viewers) who have not been trained as wildlife biologists.

Such a diverse team should be able to put all the information together into a coherent picture that the public can fully trust on how to assure the long term health and productivity of our moose population without turning state lands into giant game ranches that benefit rich sportsmen more than average Alaskans.  Even if all this group accomplishes is to verify ADF&G findings, it will help restore the public’s right to learn those results without censorship for political correctness.

Final results should be presented at a conference where team members are available for detailed queries from the public.  Day 1 of the conference should be devoted to science -- especially to identifying ways of meeting moose population goals with minimal impact on other wildlife. Day 2 should focus on the legal, social, ethical and economic pros and cons of intensive predator control, going beyond what the National Academy of Sciences achieved in its 1997 analysis Wolves, Bears and Their Prey in Alaska.

This conference should be sponsored by a neutral institution such as the University of Alaska.  Regarding Kenai Peninsula moose, the Kenai River campus (i.e., Kenai Peninsula College) might be ideal.

Would that critique and public education program be expensive?  Not compared to ex-Gov. Palin’s $400,000 program to sell Alaskans on Intensive Management.  Indeed, it would be small change compared to the millions being spent by the Legislature to transplant small numbers of moose out of Mat-Su communities and to kill predators even in regions where that may be counter-productive.

Stephen F. Stringham, Ph.D., is a consulting wildlife biologist and president of WildWatch LLC. He began his career researching moose on the Kenai Peninsula and went on to help pioneer a new strategy for managing hoofstock populations that markedly increases their productivity -- a strategy that inspired Alaska’s own management of moose and sheep. He earned his doctoral degree studying bears, then investigated predator-prey relationships. For the past two decades, his research has focused on wildlife behavior, the subject of his many newspaper articles and several books, including the Alaska Magnum Bear Safety Manual and When Bears Whisper, Do You Listen?

The views expressed here are the writer's own and are not necessarily endorsed by Alaska Dispatch. Alaska Dispatch welcomes a broad range of viewpoints. To submit a piece for consideration, e-mail commentary(at)