Greater Yellowstone Bison show signs of inbreeding.

Government slaughter could irreparably harm bison species.

Buffalo on Horse Butte © Ken Cole

Recently I referenced unpublished data indicating that bison suffer from compromised mitochondrial DNA which could be exacerbated by government slaughter without any examination as to how it will affect the already genetically compromised herd.  That information has now been released.

Historically, bison have gone through what is known as a bottleneck where the population declined to such a low number that their genetic diversity became severely limited. The Yellowstone herd of bison is derived of only about 50 individuals, half of which were brought in from other areas such as northwest Montana and Texas. In recent years, while conducting repeated culling – where greater than half of the Yellowstone herd could be killed either by slaughter or winter kill – government managers never studied how their actions affected the genetics of the bison. For example, prior to the winter of 2007/2008 the population was estimated to be 5,500. That winter 1,631 buffalo were killed by the government and hunting but an additional 1,500 died from starvation due to the harsh winter that they were unable to escape because their habitat has been so curtailed by the policy of Montana and its greedy livestock industry. This left only 2,300 bison, or less than half of the bison herd, the following spring and possibly irreparably harmed the remaining genetic diversity of the herd.New information indicates that 80% of bison in the Greater Yellowstone region carry mutated DNA in their mitochondria, which is only passed from generation to generation by the female. Because many of the slaughter events remove entire matrilineal groups which travel together in groups of 30-60 animals, the culling does not randomly remove these important genes.

Dr. Thomas Pringle, a biochemist on the genomic team for the University of California at Santa Cruz, used the unpublished Gardipee Masters Thesis, to determine that he could use the data obtained from the gene sequencing to find out which genes it coded for in the mitochondrial DNA. He noticed that the sequencing showed mutations which are detrimental for nearly 80% of the samples taken. Using the table showing the incidence of each haplotype from the herds sampled he was able to show the incidence of healthy versus unhealthy DNA within each herd.



V98A I60N

V98V I60I

% Healthy


Hayden Valley





Lamar Valley





Mirror Plateau





Antelope Flats





Wolf Creek









Dr. Pringle has released this information before it could be peer reviewed because of the impending slaughter of 400 bison captured at Yellowstone’s northern boundary which he, and others, worry could irreparably harm the nation’s last genetically pure herd and cause them to become severely inbred.

The abstract of his study states:

North American bison have rebounded from near-extinction in the nineteenth century but from such small inbred founding populations that once-rare deleterious nuclear gene alleles and mitochondrial haplotypes are now at high frequencies. The initial bottleneck was compounded by decades of unnatural selection affecting bison conservation genomics and undercutting restoration initiatives. The genomics era began in late 2010 for bison and sister species yak with the release of 102 whole mitochondrial genomes, displacing earlier control region and microsatellite data not extending to coding regions. This allows detection of both sporadic and sub-clade level mutations in mitochondrially encoded proteins and tRNAs by comparative genomics methods: deleterious mutations in both cytochrome b (V98A) and ATP6 (I60N) occur within a single common bison haplotype. Since similar mutations in human and dog cause clinical impairment of mitochondrial oxidative phosphorylation, these bison are predicted to be significantly impaired in aerobic capacity, disrupting highly evolved cold tolerance, winter feeding behaviors, escape from predators and competition for breeding. Because Yellowstone National Park bison are subjected to genetically uninformed culls and surplus animals used to seed new conservation herds, mutational status has significant implications. Continuing take of the remaining bison with wildtype mitochondria may recapitulate errors of nineteenth century bison stewardship bringing bison conservation to the point of no return.

You can read his study at the Nature Precedings website
PDF (603.5 KB) free full text

Dr. Pringle goes on to say:

Recovery of a species from a severe bottleneck requires consideration of both nuclear and mitochondrial genomics (1, 2) because inbred reduced populations may have lost much of their former genetic diversity and harbor unnaturally high frequencies of deleterious alleles (3). Inbreeding depression in Florida panthers (4), collapse of the pygmy rabbit captive breeding program (5), facial tumors in tasmanian devil (6) and required rescue of the Texas State Bison Herd (7) have put such concerns on center stage.

85 pages of supplemental material at UCSC comparative genomics

Reuters ran a story about this yesterday.

Study links Yellowstone bison fate to genetic flaw – Yahoo! News.
By Laura Zuckerman – Reuters



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  1. Dan Avatar

    Not to hijack this post but what about the elk in the Lolo. They come from a small herd. (brought in on the railroad after the Great Fires of 1910) Their numbers are being pummeled. (wolves not “greedy livestock industry”) Is anyone concerned about their genetics? Has anyone checked them for mutated DNA? At what point do we get concerned about their inbreeding?

    1. Ken Cole Avatar

      Elk in the Lolo are just one part of a very strong and large population with healthy gene flow with other areas. There should be absolutely no concern with the health of their genetics as they are not isolated from other herds like bison are. They did not pass through a genetic bottleneck like bison did.

      Frankly, your concern seems a bit ridiculous and wolves are not the primary cause of their decline. Habitat issues are the underlying cause of their decline.

      It seems apparent that you don’t understand population ecology and metapopulation theory.

      1. jdubya Avatar

        ken, not sure your “bit ridiculous” comment is really needed. Seemed like Dan asked a useful question.

        This study is quite interesting and obviously enormously pertinent to the continued culling/killing of bison. Over time, a balancer mutation might occur to offset these deleterious mutations. But evolutionary time is not the same thing as human killing time…this could really lead to the extinction/extirpation of the animals in climates that these mutations put them at risk. Maybe they’ll all have to move to southern Utah.

      2. Ken Cole Avatar

        You’re right. Sorry. I react a little harshly when I see comments like that.

    2. mikarooni Avatar

      I’m personally concerned about the inbreeding in some of the human populations in the region. I suspect some of the extreme political beliefs may be a result.

      1. jon Avatar


      2. skyrim Avatar

        You and many others mik. There are signs of it showing up all over.

    3. mikarooni Avatar

      Maybe they’ll all have to move to southern Utah.

      1. Ralph Maughan Avatar


        I know you are probably being sarcastic, but inbreeding really is a problem in some stagnant, of stagnant-until-20-years-ago rural communities.

        A former student from a small SE Idaho town had a brother that died of hemophilia.

      2. jdubya Avatar

        There is a fumarase deficiency in the polygamous families of southern utah that is devastating. And even though it can be detected by genetic screening, these people would prefer to try to raise a severely handicapped child instead of using a selective abortion practice. Some past societies would simply place such a child outside the house and let it be carried off and devoured. Seems to make sense to me.

      3. wolf moderate Avatar
        wolf moderate

        I’ve heard that Darwin married his cousin and had kids.

  2. Pedro Avatar

    Also wolves take the weak old or young animals and abnormal (maybe genetically inferior) animals. This skims animals from different population groups and is not conigned to one herd. The deers genetic legacy should not be affected by predation of wolves.

  3. Dan Avatar

    The Idaho fishing and game claims wolves are the primary cause of their decline;

    and there is good evidence habitat is not the cause;

    and as far as bottleneck goes…Do you know the history of elk in the Lolo zone in Idaho? Do you know the origins of the herd? At one point, after an unsuccessful gold rush and after the 1910 fires elk herds in the area where nearly wiped out. I have never claimed to understand genetics. I am not a geneticist or a population ecologist. What I do know is that at a couple of times the elk in that area were nearly wiped out. Did that cause genetic damage? Is it possible that genetic damage could result if numbers get low enough now? If so what are those numbers?

    1. jon Avatar

      In the early 90s, the lolo elk herd was declining. Hunters harvesting too many bulls is the reason why the lolo elk herd is the way it is today. It was not caused by wolves, but by hunters themselves by killing too many bulls.

    2. Ken Cole Avatar

      Genetic damage, or loss comes when an isolated population declines to extremely low levels. The Lolo elk are not isolated from other elk herds. Also, the Lolo elk can move to other areas where habitat is good. The declines in the Lolo area were seen long before wolves came to the area.

    3. JimT Avatar

      Dan, search the archives here for very thorough, sometimes contentious debates on Lolo elk. Bottom line..even the state’s own report suggests the wolves are not the primary cause of a decline that predates the wolves, and whose decline has somewhat stabilized according to the graph.

      Ken is exactly right in his comments, by the way. And I would gently suggest to you that if the LoLo elk were wiped out in the past, one should look to overkilling by hunters. You would do better with specifics..what years, what reports, etc.

  4. Save bears Avatar

    Habitat is one of the main reasons for the decline in the Lolo herds, not the hunting and not the wolves…Do some research Jon..

  5. Dan Avatar

    Sorry for the hijack…this is obliviously not going to be clear and concise ….back to the bison

    1. Alan Avatar

      Dan, the simple and plain answer is that the elk in the Lolo are not being hazed back into the Lolo, or sent to slaughter, whenever they try to leave. There are other herds, members of which, can and likely do migrate into the Lolo, and members of the Lolo herd are free to migrate out, which has apparently happened because of decline in the habitat. Someone correct me if I am wrong, but I believe the fires of the early 1900’s actually improved the habitat for elk by opening up the understory. It is the heavy regrowth since that has hurt the habitat as far as elk are concerned. When Lewis and Clark passed through the area they found very little game and were forced to eat candle wax and horse meat.
      Regarding the bison, is there a chance this might help get them listed as threatened? Even a small one? Anyone?

      1. Save bears Avatar

        Probably not, I know there have been many that have tried.

      2. Ken Cole Avatar

        I disagree with Save Bears on this. I do think that this new information will be helpful in an ESA listing petition.

      3. Save bears Avatar

        I hope so Ken, I really hope so, you disagreeing with me is nothing new, but I do hope that my 20 plus years of experience in this is wrong..

      4. Save bears Avatar

        An I will add, 20 + years of having smoke blown up my ass from courts, organizations and the NPS, has left me with a real bitter taste in my mouth.

        How long you been working on the Bison issue Ken?

      5. Save bears Avatar

        Thanks Ken,

        I was just curious..

      6. JimT Avatar

        I will add that you missed some big contributors to that ass warming breeze…state fish and game officials, ranchers, big trophy hunt folks to name a few…:*)

  6. Nancy Avatar

    On the other side of the country, on a much smaller scale, yet it has a familiar “ring” about it, when it comes to the controversy here over wildlife:

  7. Ralph Maughan Avatar

    Dr. Pringle has done very important work showing the dire genetic condition of the Yellowstone Park bison.

    All the bureaucrats and livestock politicians see it that bison numbers have recovered a bit since the last slaughter.

    One of these springtimes the calves born will fail to thrive or die as miscarriages.

    The will hardly bother the politicians since they hardly care about the education, health or vitality of their human constituents.


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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Ken Cole