17 Apr

F51 – Honoring the Life of a Female Cougar


F51, an adult female cougar tracked through Panthera’s Teton Cougar Project (TCP), meandered toward the eastern edge of her range, her two female offspring bouncing like electrons in orbit around her. Who can say what a cougar 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 a local wolf pack that stole F51’s last kill. Her kittens were fat, healthy and growing fast.

M85, an adult male also tracked through the TCP, sat on his own kill at the base of spectacular red cliffs. He heard F51 and her kittens approach as they 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, perhaps F51’s kittens were exposed in front of her and she charged, but whatever the scenario, she engaged him. The pair met in a storm of claws and fury, packing the snow as they wrestled. They slid down the hill again and again, rolling 60-70 feet, and leaving behind great tufts of fur. In the last great tumble, the pair slammed into a young fir tree, snapping off its lower branches.

At the end of the battle, F51 lay dead – a case of intraspecific killing, in which an animal kills another animal of its own kind. F51’s kittens fled at the first sign of trouble. At seven months of age and without a mother, their futures are bleak. Kittens typically need to be older than a year to survive on their own (Elbroch and Quigley 2013).

While a blow to the Teton Cougar Project, F51’s death has triggered a variety of questions about cougar behavior, including why this clash occurred and whether solitary cougars are always so aggressive toward each other. Infanticide involves the killing of young offspring by an adult animal of the same species, which, some evidence suggests, might induce estrous in females and create future mating opportunities for males. Cooley et al. (2009) proposed that infanticide of cougar kittens by adult males increases in hunted populations, where there is regular male turnover, and in leopards, males have killed females defending their cubs (Balme and Hunter 2013).

F51 and her kitten 'Lucky'

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.

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 F51 defending her kittens. This, in turn, leads us to another question: is it common that clashing cougars results in the death of one or the other?

According to 13 years of research, the answer is yes and no. Yes, in that we have documented cougars killing other cougars of every age. Over 13 years, the Teton Cougar Project has documented 2 of 68 kittens killed by cougars, and 2 more killed by an unidentified predator, which could have been cougars. Three sub-adult cougars were killed by other cougars, and now five adults we’ve tracked were killed by their own kind.

So yes, it happens, but it’s also rare. Our research has revealed that adult cougars interact with far greater frequency than we ever imagined, and that only 5-10% of interactions involve aggressive physical contact. Cougars, we have found, are surprisingly tolerant of each other. While this makes F51’s death more of an anomaly, our team continues to work to answer even more questions that have arisen - Will F51’s kittens survive on their own? Will the female cougar glimpsed in F51’s range set up residency there? Will a new male move in to fill M29’s territory, or will M85 migrate west into the open territory?

Panthera’s team placed the first ever cameras in a cougar den and witnessed amazing intimacy between F51 and her kittens, never before seen in the wild.

F51 was an icon for the Teton Cougar Project, providing Panthera’s scientists with invaluable insights into cougar social systems, movements and fecundity. While making a vital contribution to the health of the Tetons’ cougar population, F51 also served as the star of National Geographic Wild’s American Cougar.

Led by Panthera’s Teton Cougar Project Leader, Dr. Mark Elbroch, our team began tracking her at the beginning of 2011, just before she gave birth to her first litter (5 kittens!). In 2012, she separated from her three surviving kittens and gave birth to three more just 16 months after her first litter. Wolves killed two of these kittens, and when F51’s last remaining kitten was just nine months old, they went their separate ways. Baffled as to why such a young cougar set out on her own, our team quickly learned that F51 was pregnant yet again, giving birth to four more kittens in 2013. Since last fall, F51 lost one kitten to winter exposure and a second to unknown causes (potentially wolves).

The life of a cougar kitten is fraught with challenges, including other predators and frostbite, but our team is hopeful that two of F51’s kittens from her first litter successfully set out and now have territories of their own. Given that F51’s death is considered “natural,” our team will watch and document the survival of her two remaining kittens.

While sobering, the documentation of the loss and survival of cougars is vital in explaining the threats facing these cats in the Greater Yellowstone Ecosystem, and to create better conservation plans for the species. To do so, our team is documenting cougar territories, habitat and prey selection, foraging ecology, population dynamics and interactions with other carnivores. Over 13 years, the Teton Cougar Project team has monitored more than 120 individual cougars. And today, while we lament the loss of F51, our scientists push on, striving to protect and unveil the secret life of the American cougar.

Read posts by Panthera’s Teton Cougar Project Leader, Dr. Mark Elbroch, on National Geographic’s Cat Watch Blog.

F51 plays with her kitten, nicknamed ‘Lucky’ by Panthera’s Teton Cougar Project scientists.

F51 exhibits a low contact call-- a low rolling rumble--to call her kittens.

F51 caching, or covering, her kill. Note that she appears to have a saggy stomach because she was nursing at the time.