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Haemig PD (2013) The Value of Wolves. ECOLOGY.INFO 35

The Value of Wolves

Note: This online review is updated and revised continuously, as soon as results of new scientific research become available.  It therefore presents state-of-the-art information on the topic it covers.

Before its persecution by humans, the wolf (Canis lupus) had the greatest distribution of any land mammal in the world except man.  Its immense range included most of North America, Europe, the Middle East and Asia.  Wolves were exterminated from much of this vast area, however they have now returned to many localities where they formerly lived.  Nevertheless, intense and violent persecution of wolves continues to this day.

Ironically, many of the people who passionately exterminate wolves and act as though the wolf is "humanity's greatest enemy," are at the same time loving dog owners who regard the dog, a descendent of the wolf, to be "man's best friend."  Their attitudes seem especially contradictory when one considers the fact that pet dogs, like wolves, sometimes kill livestock and other pets (see below). 

In addition, each year, dogs kill or injure many more people than wolves.  In 2012, the World Health Organization reported that, worldwide, over 55,000 people die annually of rabies, 99% of them infected by dog bites.  Children are especially at risk, since they are bitten by dogs 3-5 times more frequently than adults (Overall & Love 2001).

Although wolves too can be infected by the rabies virus and spread it, they almost never bite humans because they do not live in close association with humans (Yalcin et al. 2012).  Transmission of rabies from wolves to humans is consequently rare compared to dogs.  Thus, it could be legitimately argued that dogs are a much greater hazard to humans than wolves.

Many citizens are curious about wolves and would like to know more about them.  Unfortunately, news media do not always supply the public with complete and reliable information.  Researchers explain why:

"News media are attracted to controversy, and wolf recovery, depredations, control programs, and most any other wolf-related topics seem irresistible.  The Yellowstone wolf reintroduction was intensively covered by sixty international media.  Popular information about wolves is often biased or inaccurate (Blanco 1998; Mech 2000). When wolf stories appear, the extreme views of opponents and supporters of wolves are often highlighted, further polarizing the issue.  The way the media covers wolves leaves the impression that they are more of a problem than other animals (Bangs and Fritts 1996)"

Because wolves sometimes kill livestock and pets, they incur the wrath of ranchers and pet owners. However, one of the most distressing aspects of the recent debate about wolf restoration has been the media's fixation, almost exclusively, on this one aspect of human-wolf interactions.  The debate is therefore biased, focusing mainly on the negative and ignoring the many positive ways that wolves benefit humans.

This review summarizes some of the ways, both positive and negative, that wolves interact with humans. We hope that it will help people on all sides of the wolf debate think more clearly about the issue.  Our analysis is based on the best information currently available, but we emphasize that more research needs to be done on all of the topics discussed.  Science still has much to learn about the wolf.

Predation on Beaver

Each year, beaver (Castor canadensis & Castor fiber) cause millions of dollars of damage to human communities by constructing dams that flood roads, railroads, houses and farmlands (McKinstry & Anderson 1999; Jensen et al. 2001). 

Beaver also damage and destroy valuable timber resources by flooding forests, girdling trees, cutting down trees and eating tree seedlings (Bhat et al. 1993; Conner at al. 2000).

In addition, beaver plug up irrigation ditches and culverts with wood, forcing landowners or taxpayers to hire someone to clean up the mess and restore waterflow (Jensen et al. 2001).

Many large predators occasionally prey on beaver, however only the wolf does so regularly and to the extent that it has the potential to control numbers of beaver (Shelton & Peterson 1983; Potvin et al. 1992).  

For example, a study in southeastern Alaska, found that 31% of wolf feces contained the remains of beaver (Kohira & Rexstad (1997).  Significant frequencies of beaver remains were also found in wolf feces in Latvia, Minnesota, Belarus, Quebec and eastern Ontario, indicating that this food habit is common and widespread (Andersone & Ozolins 2004; Fuller 1989; Chavez and Gese 2005; Sidorovich et al. 2003; Ballard & Rogers 2001; Forbes & Theberge 1996; Quinn 2005).

Not surprisingly, beaver are afraid of wolves.  Experiments show that beaver avoid forest trails where wolf scent has been placed, but continue to use trails where wolf scent is absent (Severud et al. 2011). This fact may have some ecological significance, such as reduction of beaver tree-felling on trails used by wolves.  However no one appears to have studied this topic.

In Quebec, an experiment was conducted to test the effects of wolves on beaver populations.  Two large areas (each 265-275 km2) were compared, one where wolf numbers were reduced 60%, the other where wolves were protected. 

In the area where wolves were reduced, beaver numbers increased by 20% (Potvin et al. 1992).  However, two years after wolf reduction ended, beaver numbers declined to their former levels (Potvin et al. 1992).  An important management recommendation coming from this study was that humans should not reduce wolf numbers when beaver density is high.

Wolves that prey upon beavers provide an economically valuable service to human society.  Of course, trapping can also reduce or limit beaver numbers, but it is often not effective.  This is because trapping is most needed when beaver are abundant.  However, at that time, the higher beaver numbers create an oversupply of pelts, causing beaver fur prices to decrease and reducing the economic stimulus for trapping. 

Another reason that trapping (and hunting) of beavers is often not a realistic solution is that, to be successful, all landowners in an area need to participate.  Practically speaking, such cooperation is usually difficult to orchestrate because landowners frequently disagree about the ethics or desirability of trapping (and hunting).

Because the wolf is a wild animal, it does not need permission to hunt on private property and can enter any tract of land to catch beaver.  It is hungry even when beaver pelt prices are low.

Predation on Ungulates

Wolves prey extensively on ungulates (hoofed mammals) (Chavez & Geese 2005; Echegaray et al. 2010).  Examples of ungulates are deer, moose and wild boar.  These depredations either reduce ungulate numbers or lower increases in them.  Wolves are best able to reduce ungulate numbers during periods of adverse weather or in company with other large carnivores (Mech & Peterson 2003).

Wolf predation on wild ungulates is a valuable service to human communities for 3 reasons:  (1) wild ungulates cause many traffic accidents, (2) wild ungulates feed on and kill seedling trees, reducing regeneration of economically valuable timber species, and (3) ungulates are blood hosts of ticks.  Where there are many ungulates, tick numbers and tick bites on humans increase dramatically.

In Sweden, a country the size of California but with only 9 million human inhabitants, ungulates cause thousands of collisions each year with automobiles.  In one year alone (2010), the following number of such collisions were reported in Sweden:

Ungulates colliding with cars Collisions
Moose (Alces alces) 7,227
Roe Deer (Capreolus capreolus) 36,107
Red Deer (Cervus elaphus) 246
Fallow Deer (Dama dama) 805
Wild Boar (Sus scrofa) 2,445
Total 46,830

One can imagine how expensive it was for car owners and insurance companies to repair all the automobiles damaged in these 46,830 collisions.  The worst accidents were those involving moose (Alces alces), where 5 people were killed and 42 seriously injured (Statistics from Trafikverket).  Collisions with moose are especially dangerous because the long legs of the moose elevate the bulk of its large body to the level of the car's windshield.

The wolf is the major predator of moose and also preys extensively on the other wild ungulates.  While no studies have yet investigated how many car accidents are prevented by wolf predation, and how much money the wolf saves car owners, it seems reasonable to hypothesize that the wolf's contribution to traffic safety and economics could be even more significant if its populations were fully restored.

Wolves and Public Health

There is growing evidence that some predators, such as wolves, may benefit public health by killing sick wildlife that spread infectious diseases from wild animals to humans and domestic livestock.  So far, only preliminary studies on this question have been made, however they show intriguing results that need to be followed up with additional research to establish cause and effect.

For example, Tick-borne Encephalitis (TBE) is a serious life-long disease with no known cure.  Each year, it destroys the quality of life of thousands of humans in Europe and Asia.  A recent study in Sweden found that an increase in the numbers of red fox (Vulpes vulpes) was correlated with an increase in the number of human cases of TBE the following year (Haemig et al. 2008, 2011). 

Wolves cause dramatic declines in the numbers of foxes (Palomares and Caro 1999; Elmhagen and Rushton 2007).  They do this by killing foxes and scaring them away from the areas frequented by wolves.  In the Stockholm region of Sweden, where wolves have been exterminated, there have subsequently been large increases in the numbers of red foxes and in human TBE cases (Haemig et al. 2008; 2011).  Researchers therefore wonder if the frequency of human TBE could be reduced by restoring wolf populations there to their former abundances (Haemig et al. 2008; 2011).

We can ask similar questions about other diseases like rabies. Medium-sized carnivores such as feral dogs, red fox, gray fox (Urocyon cinereoargenteus), Raccoons (Procyon lotor) and raccoon dogs (Nyctereutes procyonoides), are important hosts, reservoirs and vectors of the rabies virus (Tang et al. 2005; Kim et al. 2006; Sidorov et al. 2010; Yousey-Hindes et al. 2011).

Since wolves drastically reduce the numbers of these medium-sized carnivores in an area, one wonders if wolves reduce the spread of rabies to humans, livestock and pets.  One also wonders if the wolf's contribution to public health could be enhanced even more by vaccinating wolf packs (feeding them baits soaked in oral rabies vaccine).

Predation on Livestock

Wolves sometimes kill livestock, causing economic loss to farmers and ranchers.  However, a study in Minnesota found that even when livestock densities were high, and the densities of deer and moose were low, wolves preyed mostly on native species of wildlife (Chavez & Gese 2005).

The number of livestock claimed to be killed by wolves is frequently exaggerated.  One reason is because government programs usually compensate owners for livestock lost to wolves, but do not pay money for livestock killed by other predators such as coyotes, foxes, feral dogs and pet dogs.  Hence, there is a strong economic incentive for farmers and ranchers to claim that their livestock were killed by wolves, even when wolves are innocent (Echegaray & Vilá 2010).

A typical example illustrates this problem.  In Minnesota, a farmer reported that one of his cows had been killed by wolves and demanded compensation from the state.  Investigators from the state Department of Natural Resources (DNR) examined the carcass and followed the tracks of the predator.  They quickly discovered that the cow had been killed by a pet German shepherd dog that lived on a neighboring farm (Source of information: a DNR employee).

New forensic DNA methods enable investigators to determine if livestock have been attacked by dogs, wolves, dog-wolf hybrids, or other predators.  The first case that was investigated using these new methods was in Sweden.  There two sheep had been attacked and seriously injured by an unknown predator believed to be a wolf.  However, DNA analysis of saliva around the bite wounds proved that the predator was a dog that did not live on the same farm (Sundqvist et al. 2008).

Another reason why the numbers of livestock killed by wolves is often exaggerated is that, until recently, there was no reliable method to distinguish wolf feces from dog feces.  Since most studies of wolf food habits were based on prey remains found in feces, and since so many dog feces were misidentified as wolf feces, wolves were blamed for eating livestock that were in fact eaten by dogs.

Fortunately, the similar-looking feces of dogs and wolves can now be distinguished using DNA analysis, allowing researchers to document clearly the differences in food habits between dogs and wolves.

One such study from the Basque region of Spain, found that most wolf feces contained wild prey, while most dog feces contained the remains of domestic livestock (Echegaray & Vilá 2010). It is unknown how the livestock eaten by the dogs died.  While the dogs could have killed the livestock they ate, they also could have eaten livestock that had died of disease.  Nevertheless, the results suggest once again that uncontrolled dogs may be responsible for many of the livestock attacks that customarily are blamed on wolves, creating negative public attitudes toward wolf conservation and increasing its cost" (Echegaray & Vilá 2010).

Concluding Remarks

As we have seen, the wolf has a complex relationship with humans, one involving both positive and negative interactions.  While many of these interactions are still poorly understood, it is clear that the wolf makes many positive contributions to human society and thus has value to humans.

Some people believe that only species useful to man should be preserved.  For people who view nature this way, wolf actions beneficial to humans can be used as rationales to preserve the wolf.

Like dogs, wolf packs need to be regularly taught the boundaries of acceptable and unacceptable behavior around humans, pets and livestock.  Thus, the naive view that wolves don't ever need to be controlled is clearly wrong.  However, even more incorrect is the view that all or most wolves in an area should be exterminated.  Communities that exterminate wolves lose the important contributions that these predators make to economics, public safety and public health.

So far, we have assessed the value of wolves entirely from a human perspective.  However, to be fair, we must also look at wolves from other viewpoints.

Many critics argue that it is wrong to judge wildlife simply in terms of whether or not they are useful to man and fit into the human agenda.  They point out that what is useful and valuable to humans often changes with time.  Therefore, if we base preservation of other species on the shifting sands of human desires and interests, nothing in nature will ever be safe and our attempts to save endangered species will ultimately fail.

On another page of this website, Rowan Williams, the Archbishop of Canterbury (UK), discusses a different way to think about the value of wolves and other wildlife, one that is not based on their usefulness to humans but rather on religious conviction.  Click here to read his thoughtful comments.

References

Andersone A, Ozolins J  (2004)  Food habits of wolves Canis lupus in Latvia.  Acta Theriologica 49: 357-367

Ballard WB, Rogers AR  (2001)  Summer food habits of gray wolves in the boreal forest of the Lac Jacques-Cartier Highlands, Quebec

Bangs EE, Fritts SH  (1996)  Reintroducing the gray wolf to central Idaho and Yellowstone National Park.  Wildlife Society Bulletin 24: 402-413

Bhat MG, Huffaker RG, Lenhart SM  (1993)  Controlling forest damage by dispersive beaver populations - centralized optimal management strategy.  Ecological Applications 3: 518-530

Blanco JC  (1998)  The extinction of the wolf in Spain: Account of a scientific fraud.  Biologica 26: 56-59

Chavez AS, Geese EM  (2005)  Food habits of wolves in relation to livestock depredations in northwestern Minnesota.  American Midland Naturalist 154: 253-263

Conner WH, Inabinette LW, Brantley EF  (2000)  The use of tree shelters in restoring forest species to a floodplain delta: 5-year results.  Ecological Engineering 15: S47-S56, Supplement 1

Echegaray J, Vilá C  (2010)  Noninvasive monitoring of wolves at the edge of their distribution and the cost of their conservation.  Animal Conservation 13: 157-161

Elmhagen B, Rushton SP (2007) Trophic control of mesopredators in terrestrial ecosystems: top-down or bottom-up? Ecology Letters 10:197-206

Fuller TK  (1989)  Population dynamics of wolves in north-central Minnesota.  Wildlife Monographs 105: 1-41

Haemig PD, Lithner S, Sjöstedt de Luna S, Lundkvist Å, Waldenström J, Hansson L, Arneborn M, Olsen B (2008) Red fox and tick-borne encephalitis (TBE) in humans: Can predators influence public health? Scandinavian Journal of Infectious Diseases 40, 527-532

Haemig PD, Sjöstedt de Luna S, Grafström A, Lithner S, Lundkvist Å, Waldenström J, Kindberg J, Stedt J, Olsen B (2011) Forecasting risk of tick-borne encephalitis (TBE): Using data from wildlife and climate to predict next year’s number of human victims. Scandinavian Journal of Infectious Diseases 43: 366-372

Jensen PG, Curtis PD, Lehnert ME, Hamelin DL  (2001)  Habitat and structural factors influencing beaver interference with highway culverts.  Wildlife Society Bulletin 29: 654-664

Kim CH, Lee CG, Yoon HC, Nam HM, Park CK, Lee JC, Kang MI, Wee SH  (2006)  Rabies, an Emerging Disease in Korea.  Journal of Veterinary Medicine Series B - Infectious Diseases and Veterinary Public Health 53: 111-115

Kohira M, Rexstad EA  (1997)  Diets of wolves, Canis lupus, in logged and unlogged forests of southeastern Alaska.  Canadian Field-Naturalist 111: 429-435

Mech LD  (2000)  Wolf restoration to the Adirondacks and the advantages and disadvantages of public participation in the decision.  Pp. 13-22 in Wolves and Human Communities: Biology, Politics and Ethics (Edited by Sharpe VA, Norton B, Donnelley S).  Island Press, Washington DC

Mech DL, Peterson RO  (2003)  Wolf-prey relations.  Pp. 131-160 in wolves: Behavior, Ecology and Conservation (Edited by Mech LD, Boitani L).  University of Chicago Press, USA

McKinstry MC, Anderson SH  (1999)  Attitudes of private- and public-land managers in Wyoming, USA, toward beaver.  Environmental Management 23: 95-101

Overall K, Love M  (2001)  Dog bites to humans: demography, epidemiology, injury and risk.  Journal of the American Veterinary Medical Association 218: 1923-1934.

Palomares F, Caro TM  (1999)  Interspecific killing among mammalian carnivores.  American Naturalist 153: 492-508

Potvin F, Breton L, Pilon C, MacQuart M  (1992)  Impact of experimental wolf reduction on beaver in Papineau-LaBelle Reserve, Quebec.  Canadian Journal of Zoology 70: 180-183

Quinn NWS  (2005)  Reconstructing changes in abundance of white-tailed deer, Odocoileus virginianus, moose, Alces alces, and beaver, Castor canadensis, in Algonquin Park, Ontario, 1860-2004.  Canadian Field-Naturalist 119: 330-342

Severud WJ, Belant JL, Bruggink JG, Windels SK  (2011)  Predator cues reduce American beaver use of foraging trails.  human-Wildlife Interactions 5: 296-305

Shelton PC, Peterson RO  (1983)  Beaver, wolf and moose interactions in Isle Royale National Park, USA.  Acta Zoologica Fennica 174: 265-266

Sidorov GN, Sidorova DG, Poleshchuk EM  (2010)  Rabies of Wild Mammals in Russia in 1960-2006.  Zoologichesky Zhurnal 89: 26-36

Sidorovich VE, Tikhomirova LL, Jędrzejewska B  (2003)  Wolf Canis lupis numbers, diet and damage to livestock in relation to hunting and ungulate abundance in northeastern Belarus during 1990-2000.  Wildlife Biology 9: 103-111

Tang XC, Luo M, Zhang SY, Fooks AR, Hu LR, Tu CC  (2005)  Pivotal role of dogs in rabies transmission, China.  Emerging Infectious Diseases 11: 1970-1972

Sundqvist AK, Ellegren H, Vilà C  (2008)  Wolf or dog? Genetic identification of predators from saliva collected around bite wounds on prey.  Conservation Genetics 9: 1275-1279

Voigt DR, Kolenosky GB, Pimlott DH  (1976)  Changes in summer foods of wolves in central Ontario.  Journal of Wildlife Management 40: 663-668

Wright JP, Jones CG, Flecker AS  (2002)  An ecosystem engineer, the beaver, increases species richness at the landscape scale.  Oecologia 132: 96-101

Yalcin E, kentsu H, Batmaz H  (2012)  A survey of animal bites on humans in Bursa, Turkey.  Journal of Veterinary Behavior 7: 233-237

Yousey-Hindes K, Newman A, Eidson M, Rudd R, Trimarchi C, Cherry B  (2011)  Rabid foxes, rabid raccoons, and the odds of a human bite exposure, New York State, 1999-2007.  Journal of Wildlife Diseases 47: 228-232

Information about this Review

The author is:  Dr. Paul D. Haemig (PhD in Animal Ecology)

Photograph:  One of nine wild wolves observed in the Hayden Valley Pack, Yellowstone National Park by Dave Renwald, a wildlife biologist who works on endangered species issues with the Federal Government.  Photo taken from a blind.

The proper citation for this paper is:

Haemig PD  (2013)   The Value of Wolves.  ECOLOGY.INFO 35

© Copyright 2012-2013 Ecology Online Sweden.  All rights reserved.

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