Why Do Adult Cougars Kill Each Other?

Portrait of F51, an adult female mountain lion, tracked by the Teton Cougar Project in northwest Wyoming. Photograph by Mark Elbroch / Panthera

F51, an adult female mountain lion currently tracked by Panthera’s Teton Cougar Project, meandered towards the eastern edge of her range, her two female offspring bouncing like electrons in orbit around her. Who can say what a mountain lion thinks, but from our perspective, life seemed good for F51.

The family had fed off a series of elk in quick succession, and then successfully dodged the local wolf pack that stole her last kill from them. Her kittens were fat, healthy and growing fast. How quickly things can change.

M85, an adult male also tracked by the project, sat on his kill at the base of spectacular red cliffs, content to move little and eat more. He heard F51’s approach—he likely heard the kittens—as she dropped through a narrow cleft in the rocks above his position, and he set out to intercept them. This much was clear, written out in the snow, but the next part involves some speculation.

Perhaps M85 approached aggressively, or perhaps F51’s kittens were exposed in front of her, but whatever the scenario, she engaged him. The pair met in a storm of claws and fury, packing the snow as they rolled and wrestled. They slid down the hill about 15 feet, packing another circle of snow and leaving behind great tufts of fur. Down they slid even further, to tumble and roll yet again, the first sprinkles of blood shining ruby red on the untouched snow.

Then there was a last great tumble, the pair locked tooth and claw as they slid fast and slammed into a young fir tree; the lowermost branches were snapped off in the violence. Blood and fur soaked and covered the area at the base of the trunk, where they lay long enough that their entwined bodies melted into the snow. And then she was dead, this magnificent animal, this mother of two.

M85 dragged her another 20 feet before he left her. He returned to feed lightly from her carcass, but shortly after, abandoned the area completely. The kittens fled at the first signs of trouble, but are still hanging about the area, now four days later. At seven months old and without a mother, their futures are uncertain, if not bleak. Kittens typically need to be older than a year in order to survive on their own.

F51, an adult female mountain lion, hisses to defend her food from another female that is trying to share in the kill. Photograph by Mark Elbroch / Panthera.
F51, an adult female mountain lion, hisses to defend her food from another female that was trying to share in the kill. Photograph by Mark Elbroch / Panthera.

Intraspecific killing (“intra” meaning “within” and “specific” referring to species) is a scientific descriptor for an animal that kills another animal of its own kind. When it’s humans and premeditated, we call it murder, but for other mammals, we use varied vocabulary to describe killing for reasons other than food. Interspecific (across species) competitive killing is killing another species for competitive reasons, intraguild predation describes a predator that kills another predator, and infanticide describes adults that kill young animals of their same species. Regardless of the terminology, we’re talking about death.

The horrific battle between F51 and M85 stretched 60-70 feet and was painted with blood. But as one fascinated with mountain lion social behaviors, what I really wanted to know was why it happened. And the larger question, or course, is whether solitary cougars are always so aggressive towards each other. These are the questions Panthera is trying to answer.

Cooley et al. (2009) proposed that infanticide of cougar kittens by adult males increases in hunted population, where there is regular male turnover. In fact, in this case, M85 was west of his usual haunts and in an area typically defended by M29, the resident male that had been legally killed by a hunter several months earlier. M29’s territory has remained open, and in his wandering M85 encountered F51, who we believe he’d never met before.  This might offer a partial explanation.

F51's kittens, playing. Photographs by Neal Wight / Panthera.
F51’s two kittens, playing. Photographs by Neal Wight / Panthera.

But is it common for cougar clashing to result in the death of one or the other? According to 13 years of research: yes and no. Yes, in that we have documented mountain lions killing other mountain lions of every age category. Over 13 years, the Teton Cougar Project has documented two of 68 kittens between zero and 18 months of age that were killed by other mountain lions, and two more that were killed by an unidentified predator, which might have been mountain lions. Three of 16 subadults that died or disappeared between the ages of 18 and 30 months were killed by other cougars, and now five of 36 adults we’ve tracked (two females, three males) were killed by their own kind. So yes, it happens. But it’s also rare.

Our more recent research has revealed that adult mountain lions interact with far greater frequency than we ever imagined, and that only five to 10 percent of interactions involve aggressive physical contact. In fact, F51 shared a meal with an adult male while she was still lactating in the fall, and just several weeks before her death she interacted with another adult female around a kill for several days.

Mountain lions, we’ve found, are surprisingly tolerant of each other. This makes F51’s death even more mysterious. One theory behind infanticide is that it creates future mating opportunities for the male killing the kittens, but why a male would kill an adult female is more difficult to explain with biology. Thus, we expect it had something to do with defending her kittens.

F51 was an icon for the Teton Cougar Project. She was the star of National Geographic Wild’s American Cougar as a young adult, and since has provided us insights into cougar social systems, movements, and fecundity (see fecundity, a previous blog in which she is described). Her loss is a blow for the project, but one we will weather with time. Such is often the lot of the biologist, to bear witness, document, and learn.

Will F51’s kittens survive on their own? Will the unmarked female we’ve glimpsed several times this winter in F51’s range, set up residency there? Will a new male move in to fill M29’s territory, or will M85 migrate west? And if he does, will his movements disrupt existing social relations and families? There are still so many questions.

Peruse old photos and videos of F51 and new posts about other cougars on the Teton Cougar Project Facebook page.

Panthera logo

Cooley HS, Wielgus RB, Koehler GM, Maletzke BT (2009) Source populations in carnivore management: cougar demography and emigration in a lightly hunted population. Anim Conserv 12:321–328.

Mark Elbroch has contributed to puma research in Idaho, Colorado, California, Wyoming, and Chile, and lots of other carnivores along the way. He earned his PhD at the University of California, Davis, where his dissertation research focused on puma ecology in Patagonia in the presence of endangered humeul deer. He has authored/coauthored 10 books on natural history (http://www.amazon.com/Mark-Elbroch/e/B001ILHI96) and numerous scientific articles published in peer-review journals. Mark is currently a Project Leader for Panthera, a US-based non-profit that conducts science to promote wild cat conservation worldwide.
  • Marian Hennings

    How sad that she had to die. I hope her cubs make it to maturity, but their chances are not that great considering their youth and the presence of other larger predators.

  • jac

    The snow and the how she tumbled
    may have been to her disadvantaged.
    Too something a seemingly small as the dam collar around her throat too
    could put her at a disadvantaged. You or I or the
    Biologist never wore one while fighting another cougar. So for
    them.to say

    • Mark Elbroch

      Hello Jac,

      Yes, collars must impact the animals that wear them. But in the case of fighting, researchers are more often worried for quite the opposite reasons. Collars, you see, offer some protection to the neck and throat and therefore an advantage to the animal wearing one while in a fight with an animal without one. Because of this advantage, the collar may determine the winner and in fact it may have been the weaker animal–how would this impact genetic stability and social dynamics etc? Different species attack different areas–in cougars, lethal attacks are generally directed at the head, so the collar is less an issue. But in canids, for instance, the neck and throat are focus points for attack, and the collar is in the way. Female cougars are between 50-70% the weight of an adult male as well–physically they are outmatched. And Jenna C above is correct, in this case, both cougars were wearing collars. Thank you for your comments.

  • jac

    So for them to say
    ” it should interfere with……”
    is speculation. In the real cougar
    life it impedes more than we
    could figure..Something a little as resting/ licking by neck
    movement/ to as “little” as
    dying “unquote” because the other cat
    bites around the neck but the
    collar helps keep the bite grip
    on tight and not allowing her to twist out to protect herself.
    Has anyone heard any news
    about her cubs ?

  • April Green

    We had a Cougar kill another Cougar at the Lodge I worked at in the Boulder foothills years ago. One of the guests witnessed part of the scuffle. I went out the next day and found the cache and saw the cat feeding on the carcass that night. It didn’t seem to return after that. I documented as much info as I could. The dead cat was an adult female that appeared healthy. I always assumed that it was a male that killed her, maybe for territory? Just a guess. I have photos of the carcass and notes. measurements etc. if anyone from Panthera’s interested. It is sad to lose F-51, but hopefully her cubs will make it.

  • Jenna C

    jac, why do you keep implying that F51’s tracking collar is to blame for her death? The male M85 is also involved in the project and being tracked so he is most likely wearing a tracking collar as well. F51 probably had several disadvantages but it is not very likely that her tracking collar was a major one. Her two major disadvantages being the fact that she was female and much smaller in stature and the fact that she also had her two cubs with her which often become a liability in violent situations. Protecting yourself and 2 small children might be Moore difficult than defending yourself alone…

  • Mahmoud Hamdy

    i think lack of natural resources in the wild , which the human is a big reason of it , is a reason for animals to fight and kill each other for surviving. Human is capable of this.

  • Shanaz

    I guess like with most animals of the panther species, the mother was just trying to protect her young but it ended rather sadly. I hope that the young have made it to maturity though it seems very doubtful that they have.

  • Shanaz

    I am so glad that I have joined this section of National Geographic. It’s definitely very interesting.

  • MGGN

    “In fact, in this case, M85 was west of his usual haunts and in an area typically defended by M29, the resident male that had been legally killed by a hunter several months earlier”

    What do you mean by “legally killed by a hunter”? do you mean a human killed the resident male in that area? why? why is it legal? that could have made a big impact on F51’s destiny as M85 wasn’t a resident from that area but M29 was. As M29 was killed that area was defended by no one makin M85 appear and kill F51. isn’t Panthera a leader in wild cat conservation?

    • Mark Elbroch

      Yes, it was legal. Panthera does not decide hunting laws–this is the responsibility of the Wyoming Game and Fish Department, and its constituency, the people of Wyoming. Panthera’s job is to provide the data needed to assess whether management is working, and potentially needs to be changed. By showing low cougar survivorship and quantifying the effects of hunting on the local population, we hope to influence management. But the final decision will never be with Panthera, and will remain with the state wildlife agency (which is hopefully influenced by public opinion). Thus Panthera’s work is particularly important, so that people and Agencies can make informed decisions based on facts rather than rumors and old mythology.

  • Edontes

    I think there’s so much about nature that we don’t know about, and things that can be hard to prove. I honestly think that this F51 cat instinctually knew and felt that M85 was dangerous for some reason. The fact that she shared a meal with another previous male with no problems, might indicate that animal senses are even more so keen as to other animals’ behavior or “personality”. She hung out with that male lion. shared a meal. nothing happened. because maybe that male was had a calmness to him. something she sensed. But when she came across M85, her cubs were out in front of her, she was in proximity to him and maybe she could just “tell” and feel and sense that this cat was dangerous. that for some reason, unexplainable and unprovable, this cat was different. he was a threat. and by that sense, and with her cubs out in the open, she reacted. to protect them. to try and kill M85, because something about him said he was going to injure, kill, or hurt her or her cubs. and that’s not something that can be proven. you can’t “prove” that she felt that way, and that she had a gut instinct that M85 was SCAR from the lion king. she just felt it. and that’s kind of the cool mystery of nature itself. and something that makes what you guys are doing, and all the research, and the search for knowledge so much fun and interesting. and perhaps necessary. Great article. I hope the kittens make it. I know the odds are stacked against them, but if nature teaches us anything at all… it’s that anything can happen.

  • Yvette

    It’s a terrible loss of a beautiful big cat,and it will be even more terrible to lose her kittens.My hope is someone in cat conservation will help these kittens to survive.And to the hunter who legally killed the other cougar,shame on you for killing one of Gods most beautiful creatuers

  • mohamad pourdadash

    What happens in the nature is acceptable though at times brutal and in this case maybe meaningless and unnecessary,but killing these magnificent creatures*legally* is shameful.It makes me feel sick.

  • Ashley Goncalves

    I am a marine biology major here at Rutgers. I am a very biology-oriented individual and treasure the rights of animals. I believe in hunting so long as it is done humanely, and sustainably. To not kill an animal on the basis that it is beautiful is a poor argument, and a dangerous one at that. One could simply say that another animal is ugly, and thus justify its death. There is a strict code of ethics that us hunters follow when we head outdoors to bag game. In the hunting community, those who do not follow those ethics are shunned, and rightly so. It saddens me that some of you on here feel it necessary to call hunters “cruel”. The hunting community is a leader in the conservation movement: they are more intimate with the outdoors than most individuals who sit behind their computers and sign anti-hunting petitions online.

  • Vicky L Ford

    It’s sad to say, hunting cougars in the wild is legal in several states at certain times of the year. Their a beautiful animal and like so many others deserve to live free. But sometimes their circumstances and health, just like the wolves, start killing livestock. That’s someones life affected and their answer is the legal hunting of the animal. Others just kill to have a hide and bragging rights. I have a friend who hunts cougars. If it’s a female, he won’t shoot it. Not for any noble reason except males are bigger. it makes me sad to watch people destroy what was here first.

  • Stop killing lions

    When the hunters actually hunt and kill a cougar they arn’t just killing one. Multiple deaths occur afterward. This story is a perfect example. If the resident male had never been killed this probably wouldn’t have happened. But this male feeled the vacuum caused by the resident males death. As a result possibly four lions will die. And for what? What satisfaction could you ever get by killing animals like this? What are you idiots going to do when youve killed them all? Open a damn book and admire the pictures?

  • Hank Hovorka

    I think we all need to educate ourselves before commenting. Adult male cougars regularly kill the kittens of other male rivals, I find it difficult to believe this person has only documented two such killings in 13 years. However my favorite argument to anti hunting comments, involves cougars, after the residents of the urban areas of California voted to ban legal regulated cougar harvesting in there state the very next year, more cougars were killed by state wildlife officials “as nuisance ” animals than ever harvested by hunters. These cougars were simply disposed of in dumpsters. Due the research and check it out for yourself.

  • Joan Austin

    It just seems sad to me that you track the big cats and get close enough to take pictures of them. You document their lives. Follow them and their cubs. Then the state in their wisdom sees fit to allow hunters come in and kill them. None of it makes any sense to me. A lot of big cats today are nearly extinct because of so called hunters getting their trophies and a lot of them not legally. It is a shame that F51 had to defend her cubs and die because M29 was gone. Now maybe four magnificent cats will be dead and for what? So some hunter can have his trophy? Shame on all of you.

  • Gary MacKinnon

    It seems the chances of those 2 cubs surviving without the protection of their mother would be very poor. At approx 6-7 months of age they would not have had the ability to hunt successfully. Several years ago, while on a business trip to Missoula MT, I went on a 2 hour hike in the hills above the town after a light snow. Retracing my steps back to the motel, I saw in the snow evidence that I had been followed by a mountain lion. The paw prints were huge! In retrospect, it was probably within striking distance, but I never saw it. I got lucky only because a rancher came driving up the dirt road I was returning on and that must have scared off the cat. I can’t imagine that those 2 young, inexperience kittens could stalk & then successfully take down prey without their mother’s help & guidance. So that one “legal hunted” & killed male lion probably likely cost the lives of 3 more. A total waste!

  • Buddypup

    Most of the comments relate to cats that live in the west. We have a small number of mountain lions in eastern North Carolina that law enforcement and animal “experts” say are large bobcats. We have seen these animals within 20 feet while it was chasing a deer or crossing a dirt road. Spotting these animals has increased over the last 5 years as large tracts of forest are cut for farming. When will we get some expert coverage here. There are still quite a few deer in our area and I am told that humans are not high on the mountain lion favored snack list as long as there are gourmet deer out there. And that once locked on an animal for dinner, the lion wont break lock until the animal is taken or escapes. But we have concern for the sheep, goats, and our non-farm animals that live in the area when the deer are gone.

  • Nihal

    Hi Mark
    I am crazy about f51 I love her.I am interested her days.I wanna learn about her life (detailed) . Can you write blog about f51? Thank you dr.elbroch

  • berkay

    ı love f51 so much..and ı wanna read blog about f51(detailed) can you write blog about f51 dr elbroch? thank you!

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