Changing Planet

Overlapping Mountain Lions

F51 and her female offspring, F70, seated near an elk cow killed by F51. Photograph by Mark Elbroch / Panthera.

F61 and F51, adult female mountain lions (Puma concolor), also called cougars, followed by Panthera’s Teton Cougar Project were both four years old when they gave birth to their first litters of kittens within a month of each other in 2011. The pair of big cats were neighbors in adjacent and overlapping home ranges in the Bridger-Teton National Forest, east of Grand Teton National Park in northwest Wyoming, USA.

The Teton Range, photographed from the east across Grad Teton National Park. Photograph by Mark Elbroch / Panthera.
The Teton Range, photographed from the east across Grad Teton National Park. Photograph by Mark Elbroch / Panthera.

A well-placed motion-triggered camera caught a fortuitous image of F61 and F51 spending time together in early 2012, accompanied by their four kittens (1 from F61, 3 from F51). It sparked great discussion among our team, many of whom were convinced they must be close relatives, perhaps sisters. Indeed, prevailing theory supported the idea that close kin were more likely to be close to each other and tolerant of one other. Thus, it just made sense that the two cats would be kin. At the time, however, we did not know the genetic relatedness of cougars in our study, except of course, kittens born to females we were tracking.

Mountain lions are solitary carnivores expected to interact only during the breeding season or to settle territorial disputes. In short, we expect cougars to avoid each other. The two prevailing ecological theories explaining the spatial organization of animals within populations are the land-tenure and kinship theories (e.g., Diefenbach et al. 2006; Griffiths & Armstrong 2001). The land-tenure predicts territorial behaviors—females use smaller home ranges that provide the necessary resources to sustain themselves and their kittens, while males utilize larger home ranges that provide access to numerous females for mating opportunities. Kinship theory predicts that individuals that are more closely related to each other will be clumped together within populations. Spatial clumping might also lead to higher social tolerance between closely-related individuals.

Adult female mountain lion followed by Panthera's Teton Cougar Project. Photograph by Khalil Karimov / Panthera.
Adult female mountain lion followed by Panthera’s Teton Cougar Project. Photograph by Khalil Karimov / Panthera.

In early 2012, F51 and F61 were spotted together several more times and often near carcasses of animals we assume one or the other had killed. This led to more questions and more debate among our team. Perhaps prey distributions and availability were a contributing factor in cougar interactions? So, we did our best to devise a study to begin to unravel the social organization of pumas in our study area. Our goal was to test whether home range overlap between individuals was explained by the prevailing theories—land tenure or kinship—or perhaps, by the distributions of prey.

Assumptions of the land-tenure hypothesis, including that males have larger home ranges than females, and that males will not overlap with other males, could be tested with location data and subsequent home range calculations. Anthony Caragiulo joined our team from the American Museum of Natural History in New York City to provide genetic analyses, so that we might assess kinship among cougars. That left prey distributions, which we needed at a fine enough scale to compare across home ranges and within home ranges as well. But we lacked these data, nor were they available from other researchers and wildlife managers in the region. After some creative thinking and lively discussions, we came up with the idea of “hunt opportunity”—an analysis that provided a mathematical value representing the probability that a cougar would kill prey in any given location across the landscape. Then we used hunt opportunity as a proxy for likely prey distributions.

Elk, deer, and other ungulates migrate seasonally in the Southern Yellowstone Ecosystem where we study cougars. In winter, our study area sees a massive influx of elk as they aggregate in groups of hundreds and thousands at lower elevations to avoid deep snows, and near supplemental feeding grounds maintained by the Wyoming Game and Fish Department and the National Elk Refuge. Thus we expected winter prey distributions rather than summer to better explain variation in home range overlap among individual cougars.

F51 and F61, as it ends up, were completely unrelated. F61 was born in the study area, whereas F51 immigrated in from elsewhere. The overlap between their home ranges supported higher winter hunting opportunities, as we expected given the large seasonal aggregations of prey in that season. And this pattern held true across other cougars in our study as well, as can be read in our new paper just published in the Journal of Animal Ecology. Kinship failed to explain variable home range overlap among cougars, whereas hunting opportunity and land tenure did. Our results provided an initial foundation from which to interpret our field observations of F61 and F51, and may indicate that solitary carnivores are more tolerant of sharing key resources with unrelated others than previously believed, or at least during periods of high resource availability.

Figure 1 from our paper in Journal of Animal Ecology, depicting the study area and home range overlap between several female and male cougars. Artwork by Patrick Lendrum and Mark Elbroch / Panthera.
Figure 1 from our paper in Journal of Animal Ecology, depicting the study area and home range overlap between several female and male cougars. Note that the animals depicted here are deceased, so as not to give away their territories (mountain lion hunting is legal in our study area). Artwork by Patrick Lendrum and Mark Elbroch / Panthera.

And this is just the start—we’ve launched new methods with motion-triggered cameras to better understand cougar interactions and to unravel when and why they come together. This research is forthcoming.

The full research article is available to download for free for one month from the journal itself—just click the Journal of Animal Ecology link, and then click “Get pdf” on the right and it will lead you to it. Alternatively, always feel free to request a copy through our facebook page: Continue to follow F51 and F61, and the adventures of other mountain lions as well, on our Panthera Puma Program facebook page. Thanks for reading.



Diefenbach, D.R., Hansen, L.A., Warren, R.J. & Conroy, M.J. (2006) Spatial organization of a reintroduced population of bobcats. Journal of Mammalogy, 87, 394–401.

Elbroch, L. M., Lendrum, P., Quigley, H. & Caragiulo, A. (2015) Spatial overlap in a solitary carnivore: support for the land-tenure, kinship, or resource dispersion hypotheses? Journal of Animal Ecology doi: 10.1111/1365-2656.12447

Griffiths, S. W. & Armstrong, J. D. (2001) The benefits of genetic diversity outweigh those of kin association in a territorial animal. Proceedings of the Royal Society of London B, 268, 1293-1296.

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 ( 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.
  • Marcus Grigato

    Hi Mark!
    I am a National Geographic and Panthera follower. Thanks for another new interesting article! Do males mountain lions also overlap their home range in the winter according to the the idea of “hunt opportunity”? Thank you.

    • Mark Elbroch

      Hi, Thanks for your interest. In short, we lacked sufficient males with overlapping ranges to test whether this was true. So the unsatisfactory answer is that we do not know and wish we did…

  • Patricia Messina

    I was looking forward to Big Cat Week. I tuned in on Friday, 11-27-15 to watch Cougar Undercover. To my dismay I was extremely upset after watching… I need to know why the scientist involved in this project didn’t intercept when F75 was indeed having a hard time catching prey and was found in a starving state…and to make matters worst her sibling F99 died from a porcupine quill. How can anyone from Panthera sit back and watch this poor creature suffer and die? Why was there no interaction? And how in God’s name can you call this conservation?? What are you saving? The scientist Mark Elboch sat back and did absolutely nothing…Did this sad situation not effect him? Did anyone ever think to do the right thing and bring these beautiful creatures food when their Mother F51 was killed…What about meds for F99 who died from an infection? Please I need an answer…

    • Mark Elbroch

      Thanks for your comments…we’re not sure why some of the details of the story were not included in the film, so here I’ll provide some additional background: “Interfering” with orphaned kittens, including supplemental feeding, has never been something we’ve been permitted to do (Panthera cannot make these decisions–all decisions regarding handling wildlife are made by State wildlife agencies) Thus, when F75 and F99 were orphaned, we made special requests to local State managers to do just that, repeatedly. They preferred to allow nature to play out, and told us not to interfere. Thus, we watched the orphan kittens but did not help. When F75 died of starvation, we made the request again, and then we were not only given permission by the State to feed F99, but State personnel rushed to join in the effort. This was remarkable participation from an agency under pressure to ignore carnivores. The supplemental feeding we provided to F99 was the essential aid she needed to find her feet and succeed in learning to hunt on her own. We assure you, we at Panthera, myself included, did not sit idly by and watch these kittens suffer. Some of these details were included in the post:
      Please keep the questions coming–they are important issues. Balancing morality and good conscience and good research methods is a difficult task–but we try our best, we truly do. Kind regards, mark elbroch

  • Ty

    Hey Mark. I saw your program tonight and it was incredible. I became a huge fan of cougars growing up a Washington State University fan (where I eventually attended college at). I had a few questions though please! The post says she has three kittens so what happened to the first one? I assume it died but how? I also read on the Panthera Facebook page that all 4 of F51s kittens from her third litter had also died. Again, how? I assumed the orphaned kittens from the show were her third litter. Finally, how do you know for sure that M85 killed F51? Sorry if any of these questions were answered in the show. I did step away for a few minutes.

    Also, I will be biking through Jackson Hole, Wyoming on a XC bike trip in 2016 (should be there in May) and would love to meet you and volunteer for a few hours if you’re local to the Jackson Hole area or if Panthera has offices there. Feel free to email me at the address used in the section above.

    Hope you reply 🙂

    • Mark Elbroch

      Hi Ty, Thanks for the message and your enthusiasm. I think you are referring to F61–she had 3 kittens, and the first was killed by wolves when 3 months old. The other two made it to dispersal (F96 and M80). F51’s litter of 4–the first died of exposure, the second was killed by wolves, the third of starvation after F51 was killed (F75), and the last from porcupine quills (F99). Look for F75 and F99 in other blogs I’ve posted on CatWatch–they are frequent characters and much of their story is told. I think earlier blogs will answer most of your questions. I also discuss the M85-F51 interaction in several blogs–even the recent one about the film. In brief, the story was told in footprints in the snow. Definitely reach out before your trip to Jackson–send us a message through our facebook page. Hope we’ll see you in summer. best–mark elbroch

  • Tracy Garner

    Hi Mark,
    I just recently saw a documentary about The Teton Cougar Project, I would like to know how F96 (Frostbite) is faring, hoping she has continued to thrive and make her way.

    • Mark Elbroch

      She is well, thanks for asking. Still living adjacent Jackson. Last summer, she mated with an equally young male but the union did not produce kittens…perhaps this summer will be her first…

  • Karine L

    Bonjour Mark,

    J’ai vu votre reportage aujourd’hui. C’était vraiment passionnant.
    Pourquoi M85 a ainsi tué F61 ? Avez-vous trouvé une explication à ce comportement ? C’était très triste, dur, violent et lourd de conséquences pour F99 et sa sœur.
    Merci d’avance

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