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:
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"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)"
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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.
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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
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Copyright 2012-2013
Ecology Online Sweden. All rights reserved.
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