New Study Finds that Mountain lions prey selectively on prion-infected mule deer

Could predation slow the spread of Chronic Wasting Disease?

A study conducted in Colorado, where chronic wasting disease (CWD) has become widespread among deer and elk, indicates that mountain lions prey selectively on infected individuals over healthy deer. I think that healthy populations of large carnivores like wolves and mountain lions could help slow the spread of this disease which has been found in a moose near Wyoming’s petri dish elk feed grounds. It has been shown that chronic wasting disease can bind to the soils and infect an area indefinitely exposing generations of cervids to this protein virus or prion.

It is possible that CWD has already infected Wyoming’s feed grounds since it may go unnoticed. Testing for CWD is usually done on brain tissue obtained from deer and elk that have been killed by hunters.

Mountain lions prey selectively on prion-infected mule deer
Biology Letters
Caroline E. Krumm, Mary M. Conner, N. Thompson Hobbs, Don O. Hunter and Michael W. Miller





  1. JW Avatar

    Fascinating study and yet another reason why state fish and game agencies must rethink their “harvest” management for predators incl. wolves, coyotes, and mt. lions. Not killing them could be very important to stop the flow of disease despite the constant need for “management” which was quoted on several of the articles on the successful MT wolf hunt and the hunt now closing. Most of this management, in my opinion, is to regulate predators at supposed cultural carrying capacity (whatever that may be and which differs on the eye of the beholder) and since predators regulate their own numbers, it rarely address biological carrying capacity like in ungulates.

  2. Ralph Maughan Avatar

    I suspect we will find this is true of wolves too, maybe even to a greater degree because we already know that they select prey for weakness to a greater degree than cougars.

    Cougar like to have a good position in the tree or on a cliff so they can bite quickly at a good angle.

  3. catbestland Avatar

    This could be a very good argument for re-introducing wolves into Colorado.

  4. mikepost Avatar

    Given that hunted lion meat is often consumed is there an issue with CWD within the lion population? One would think that it would have been anecdotaly noted by now if this is indeed a common trait.

  5. Ralph Maughan Avatar


    By way of generalization (which is not proof), I would think that if CWD is not passed on by human consumption of venison, carnivores are even less likely to acquire CWD.

    Carnivores eat so many things that would quickly infect people, I believe they have considerable resistance to many kinds of infections.

  6. Ralph Maughan Avatar

    Another topic, but folks have just got to look at mikepost’s grizzly photograph.

  7. jdubya Avatar

    CWD can probably be passed to any animal that has a prion protein that can be mal-formed by the ingested infectious form. I don’t know the sequence of the cat and wolf prion proteins but I would guess (based upon the fact CWD has not been found in them even though they think an infected deer is a tasty treat) that their sequences are sufficiently different to prevent transmission. It is really the more the exception of cross genus transmission (mad cow from beef to humans, for example) than the rule.

  8. dewey Avatar

    I want to add some anecdotal evidence to the topic here. Back before the year 2000, Wyoming Game and Fish managers were surprised when cases of Chronic Wasting Disease appeared suddenly in the south Absarokas-Owl Creek Mountains west of Thermopolis WY. It was found in two deer, I believe. That area has a healthy Cougar population , but they get heavily hunted. About that time, a pack of expatriate Yellowstone wolves also began frequenting the same area where the CWD had been found. The Washakie pack would range from just south of Cody all the way past the Greybull River and around the Owl Creeks over to the Wind River valley as far as the town of Dubois and the DuNoir River area upcountry to the west.

    After those wolves began roaming the area where the new cases of CWD in Deer were raising concerns, there were no more cases reported. FWIW.

    I happen to believe that wild wolves also exhibit the behavior shown by Cougars when selecting their prey…they would naturally select an ungulate with symptoms of CWD…the slower, weaker, more disoriented animals. It’s in the fundamentals of the Large Carnivore Operating Manual, I’m sure.

    However, I have tried to raise this very argument with Wyoming Game and Fish and others so adamantly opposed to wolf reintroduction and recovery anywhere in Wyoming. I preface it by saying all we seem to be allowed to hear are the negative impacts and negative actual costs of wolves , as in debits and dollars. We never ever seem to hear anything that could be posted on the positive side of the ledger, to the wolf’s credit as a positive force in wildlife management… something that might just as easily be expressible in dollar costs as are ranchers claiming dollar damages for livestock lost to large predators. The positive values of have wolves on the landscape as an ecological dynamic never ever seems to enter the high level discussion in Wyoming. Some of those values can be put in dollars straight out; others are intrinsic and qualitative but still need to be more widely expressed Currently , they are not.

    To rephrase the question: What is it worth to Wyo Game and Fish and the hunting community if a wolf takes out a Deer or Elk infected with Chronic Wasting Disease? It’s a fair question.

    At a meeting in Cody after wolves were briefly delisted in 2008 , where G & F explained their draft management plan and layed out the hunting plans for wolves in Wyoming, I asked Bill Rudd of Wy G&F if the department saw any positive value to wolves in context with chronic wasting disease or other factors, ad he flatly said Wy G&F sees no good value to wolves. They were to him and his peers a nuisance animal that had been thrust on them, and best eradicated by any means possible with extreme prejudice in the areas outside the Yellowstone zone. Rudd’s response to my question in that crowded room told me with all certainty that Wyoming Game and Fish was concretely antagonistic towards wolves and does not consider wolves to be wildlife, just a bigger varmint. To G&F , wolves have no value or negative value only.

    WHich is one reason why Wyoming is still in the doghouse with its wolf management plans…

  9. Virginia Avatar

    Dewey- as you may or may not remember, I was at that same meeting (one of about 5 people who supported having the wolves in this state/area) and I asked Rudd if they would first consider using non-lethal methods to remove wolves considered “in trouble” and he gave me a definite “no.” That meeting was a joke as far as I am concerned. WY G&F have their own agenda for certain and it isn’t as advocates for predators.

  10. mikepost Avatar

    Ralph, thx for the credit on the photo, however, it aint me!

  11. Barb Avatar

    Hunting predatory animals has always just seemed wrong to me — for many reasons.

  12. Wilderness Muse Avatar
    Wilderness Muse

    Does anyone know whether CWD prions remain viable after passing through the digestive system of a carnivore, even though the carnivore is not “infected?”

    Prions cannot be destroyed by cooking, but I haven’t seen anything on whether they are persistent in other ways?

  13. Ranman Avatar

    Given that these prions apparently sometimes spontaneously change form, I wonder if predation has stopped previous, and possibly numerous, naturally-occurring outbreaks over the millennia.

  14. jimbob Avatar

    Ralph, I find this very interesting, if proven. I’ve been trumpeting this for years, including on this website. Hunters cannot effectively control populations of ungulates in places like Arizona and Utah. There is too much inaccessible country. Predators are the only hope. If it is true that they would target diseased individuals first (remember predators eat the weak and the sick?) then they are even more important to these hunting organizations than thought before! Hunters are targeting the opposite, healthy, robust animals. They will not and cannot remove sick individuals from the population, which allows disease to flourish! A very interesting article. I’d like to hear the spin begin from hunting organizations….


Ken Cole is a 5th generation Idahoan, an avid fly fisherman, wildlife enthusiast, and photographer. He is the interim Idaho Director for Western Watersheds Project.

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