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t has long been asserted that wolvesand other predators only kill thelame, the sick, or otherwise infirm

members of a prey population. Statedanother way, “predators are commonlythought to capture substandard individu-als––those in poorer condition than theaverage individual––in higher thanexpected proportions.” Based on this oft-stated belief, it is then claimed that pred-ators not only have no effect on preynumbers, but that predation actuallymakes the prey population healthier orfitter. In other words, by killing inferiormembers of a prey species, predatorscreate higher-quality prey. Think of it asprey eugenics where inferior individualsare sentenced to death for the greatergood of the prey population. But is anyof this true? Or is this just another mythused to justify the protection and reintro-duction of predators, such as the wolf?

Interestingly, this very question wasaddressed by Dr. Stanley Temple of theUniversity of Wisconsin in a 1987 paperthat appeared in the scientific journal‘Ecology’, a publication of the EcologicalSociety of America. Dr. Temple had atrained red-tailed hawk that he flewagainst three prey species––easternchipmunks, cottontail rabbits, and graysquirrels. Dr. Temple also collected arandom sample of each prey species.Postmortem examinations were per-

formed on all the animals killed by thehawk, as well as those shot by Dr.Temple. This allowed Dr. Temple tocompare the condition of the predator-killed prey, with normal members ofeach prey species. As you might expect,chipmunks were the easiest for thehawk to kill and the predator did notselect for substandard individuals of thatprey species. Cottontail rabbits wereintermediate in their difficulty for thehawk to capture, and 21% more sub-standard cottontails were selected thanoccurred in the general population.Gray squirrels were the most difficult ofthe three prey species for the hawk tokill, with the predator capturing 33%more substandard squirrels thanoccurred in the overall population.

The results of Dr. Temple’s experimentscan be summarized as follows, “… thedegree to which substandard individualsof a particular prey species will be cap-tured disproportionately by a predator,is a function of how difficult it normallyis for a predator to capture and kill indi-viduals of that species of prey.Accordingly, when hunting a preyspecies that is easily captured andkilled, a predator will take substandardindividuals in proportion to their occur-rence in the prey population. On theother hand, when hunting prey that areprogressively more difficult to capture

and kill … the predation should take anincreasingly disproportionate number ofsubstandard individuals.” That is to saywhether or not a predator kills a dispro-portionate number of substandard preyitems, depends on the size and killingability of the predator versus the sizeand defense capabilities of the prey. Allelse being equal, a large predator willkill members of a relatively small preyspecies without regard to the age, sex,or physical condition. While the samepredator, preying on a larger speciesthat is more difficult to capture and kill,will tend to select for substandard mem-bers of the prey population.

In Europe, lynx prey upon both roe andred deer. Roe deer are less than half thesize of mule deer, while red deer arethe same species as our elk. As predict-ed by Dr. Temple’s work, lynx do notselect for substandard roe deer, but lynxdo select for the smallest-sized red deer,that is calves. Wolves, on the otherhand, do not select for either substan-dard roe deer or red deer. OnMinnesota’s Isle Royale, however,wolves do tend to select for substandardmoose, because moose are very difficultfor wolves to kill––moose, in fact, havebeen known to kill wolves. While onAlaska’s Coronation Island, wolveskilled black-tailed deer irrespective ofthat prey’s age, sex, or condition.

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Whether or not a predator selects forsubstandard individuals also depends onhow the predator hunts, as well as envi-ronmental conditions. Research hasshown that ambush predators, such asmountain lions and other cats, generallydo not select for substandard prey.While cursorial or coursing predatorsthat run their prey down, like wolvesand African hunting dogs, generallytend to take a disproportionate numberof infirm individuals, especially of large-sized prey. This makes perfect sense,because substandard animals are morelikely to give out when chased than areindividuals in prime condition.

In addition, under certain environmentalconditions, such as deep, crusted snow,even relatively small-sized predators,like coyotes, can kill large-size prey,such as mule deer, at will and withoutregard to sex, age, or physical conditionof the prey. Then too, there is the ques-tion of whether the prey animals arenaturally substandard, or are they sub-standard because they are constantlybeing chased and harassed by wolvesand other predators? As I explained inan earlier article on “Predation and theEcology of Fear” [see Muley Crazy 10(5):23-28; 2010], if humans harassed wildlifethe way predators do, the people wouldbe in jail. In a recent study in Canada’sJasper National Park, a radio-collaredcalf elk switched wintering areas at leasteight times during one two-month peri-od to avoid wolves.

As to bears and other predators thatcommonly prey on fawns and calves, Iknow of no data, which suggests thatthose newborn animals would not havelived to become adults, if their younglives had not been prematurely terminat-ed. Fawns and calves are killed notbecause they are unfit, but because theyare vulnerable and so easy to kill. Wolveson caribou calving grounds have beenobserved to kill 20 or more calves in amatter of minutes because the youngsimply cannot escape. Few of the calvesare actually fed upon by the maraudingwolves, which is true of all surpluskilling. Surplus killing can also occur

when ungulates are hindered by deep,crusted snow. Under the right conditions,even coyotes, let alone wolves, can wipeout an entire year’s fawn or calf crop injust a matter of days.

By preying primarily on the young ofthe year, bears and wolves can limitungulate numbers to 10% or less ofwhat the habitat would support in theabsence of predators. Just because apredator concentrates on fawns orcalves does not mean that the predatorhas little or no impact on the prey pop-ulation. In fact, predators that prey juston fawns or calves, can, over time, wipeout a prey population, especially if thepredators, such as bears, have alterna-tive foods, like berries or salmon. If asignificant number of new animals arenot recruited into a prey populationeach year, ultimately that prey species isdoomed. I first explained this is a 1993article I wrote on wolf recovery and it isas true today, as it was then.

It is also commonly claimed that preda-tors improve the health of the herd bypreying disproportionately on diseasedanimals. The available data, however,does not support that assumption. Wolfpredation has not lowered the incidenceof brucellosis in elk within the

Research has shown that ambush predators, such as mountain lions and othercats, generally do not select for substandard prey. While predators that run theirprey down, like wolves, generally tend to take a disproportionate number of infirm

individuals, especially of large-sized prey.

Surplus killing can also occur when ungulates are hindered by deep, crusted snow.Under the right conditions, even coyotes, let alone wolves, can wipe out an entire

year’s fawn or calf crop in just a matter of days.

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Yellowstone ecosystem. To avoid beingkilled in the predator-rich park, elk arestarting to form large herds on low-ele-vation private lands, which actually‘increases’ the risk of disease transmis-sion, both to other elk and to cattle. InCanada’s Wood Buffalo National Park,bison are infected with both brucellosisand bovine tuberculosis. Yet more than50 years of wolf predation has not low-ered the incidence of either disease.That is to say, if wolves were selectingdiseased bison, the percentage of infect-

ed bison in the herd should declineover time, but that has not happened.Similarly, if predators selected for dis-eased prey animals, then it is logical toexpect predation to limit the spread ofany newly introduced disease. Wheredata are available, though, that has notbeen the case.

In South Africa’s Kruger National Park,cape buffalo have recently becomeinfected with bovine tuberculosis. Capebuffalo are preyed upon by African

lions and spotted hyenas, both formida-ble predators, yet predation has notslowed the spread of bovine tuberculo-sis in Kruger’s cape buffalo population.Similarly, here in the West, predation byblack bears, mountain lions, and coy-otes has not slowed the spread ofchronic wasting disease (CWD) in muledeer and other cervids. CWD is a verydebilitating and deadly disease, yet pre-dation has neither slowed its spread orlowered the incidence of the disease.Not in mule deer, nor elk, nor white-tails. In a recent South Dakota study,mountain lion predation did not lowerthe incidence of CWD in elk and elkkilled by cougars, “typically were ingood physical condition and not infect-ed with CWD.”

Now, there was one study, which con-tended that compared to sport hunters,mountain lions selected for CWDinfected deer––that is mountain lionskilled a higher percentage of CWDinfected mule deer than hunters.However, that study was flawedbecause it was based on the falseassumption that hunters kill infectedand non-infected deer in proportion tothe number of infected and non-infect-ed mule deer in the entire population.That is to say, the study assumed thathunters killed deer at random, which isnot true because state game depart-ments warn hunters about CWD andadvise hunters not to kill deer thatappear to be sick or acting abnormally.In other words, hunters actually selectfor non-infected deer, which invalidatesthe entire study. Since no one knowswhat the incidence of CWD is in thetotal population, as the disease can becorrectly diagnosed only after an ani-mal is dead, just because mountainlions kill more CWD infected muledeer than hunters, does not mean thatcats select for CWD infected animals.

Moreover, not only is there no evidenceto support the notion that predatorsreduce the incidence of disease inungulate populations, but scientific dataindicate just the opposite. Namely thatpredators ‘spread’ a whole host of dis-

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eases both to ungulates and to humans.Rabies is the best known example, butpredators also spread a number of para-sitic diseases. For instance, the Canadianwolves released in Idaho andYellowstone were not properly quaran-tined and those animals have nowspread a new, potentially deadly para-site throughout their range. Echincoccusgranulosus is an intestinal wolf parasite,a tapeworm. The tapeworm’s eggs passin the wolf’s feces whereby they con-taminate the ground and vegetation.Deer, elk, and other ungulates eat thecontaminated vegetation, but since theungulates are not the proper host, thetapeworms encyst in various bodytissues where they weaken the preyanimals, making them easier for wolvesto kill. Once killed and eaten by wolves,the encysted tapeworms are not digest-ed but instead reinfect the predator.Echincoccus granulosus also encysts indomestic sheep.

Humans can become infected in at leastthree ways. First, by eating improperlycooked wild game or domestic sheepthat contains the tapeworm cysts; sec-ond, by handling infected wolves, (ifyou kill a wolf you must be careful howyou treat the dead animal, as it is veryeasy to inhale the microscopic tape-worm eggs that cling to the animal’sfur); and third, by contact with dogs,your pets, or someone else’s. Dogs, likewolves, are a primary host for this para-site and are easily infected by smelling,or rolling in, wolf droppings. This, ofcourse, includes sheep herding andguarding dogs, as well as hunting dogs.After which the infected dogs can easilyspread the parasite to humans. Think ofthe last place your beloved pet lickedbefore licking your child’s face!

People, like ungulates, though, are notthe correct host for this tapeworm, sothe parasites encyst in humans, just likethey do in deer or elk. In humans, thecysts are generally painless, and a per-son usually has no idea he, or she, isinfected until the cysts burst or rupture.Then, depending on where in the bodythe tapeworm encysted, a person can

become seriously ill or even die.Moreover cysts can lie dormant formore than 20 years, like a time bombwaiting to detonate.

All this, of course, was never men-tioned, let alone properly discussed, inthe federal wolf EIS or explained to thepublic before the Canadian wolves wereturned loose by the federal government,over state objections. It should come asno surprise then that federal officialsand their pro-wolf allies, including vari-ous state fish and game biologists, havedownplayed the effects of Echincoccusgranulosus on an unsuspecting public.Finally, unless you opt for a full bodyscan, it is impossible to tell whether ornot the tapeworms have encysted inyour body, or the bodies of your familymembers, because the cysts cannot reli-ably be diagnosed by other means.Since this is a new disease here in theWest, most doctors will not have a cluewhat is going on even after a cyst orcysts rupture, which can lead to misdi-agnosis, with all the associated conse-quences, including death.

So the next time some wolf biologist orpro-wolf advocate tries to tell you thatpredators only kill the lame, the sick,and the infirm, or that predators helpcontrol disease, listen politely, or not,and then have a good laugh! What youdo next is up to you, but remember, thefederal government has warned all itsemployees, who normally handlewolves or wolf scat, about Echincoccusgranulosus, but has yet to pass a similarwarning on to the general public.

Editor’s Note:Since Dr. Kay submitted his manuscript,a lady in Idaho has been confirmed ashaving Echincoccus granulosus cysts.Half her liver had to be surgicallyremoved and she incurred $65,000 inmedical expenses. Local doctors misdiag-nosed her condition and it was onlyafter she saw a specialist in Seattle thatshe received proper care and treatment.She had suffered for years with a diseaseunknown to local doctors.

Not only is there no evidence to support the notion that predators reduce the incidence of disease in ungulate populations, but scientific data indicates the exact opposite! The above photo shows a set of lungs from an elk harvested in Idaho. The

lungs show hydatid cysts, caused by the elk ingesting forage that had held the micro-scopic eggs of the Echinococcus granulosus tapeworm–a parasite that is now being

widely spread by an excessive number of wolves roaming the northern Rockies; creatinga health hazard for most other wildlife, livestock, pets and even humans.

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