M80 and F96, young mountain lions followed by Panthera’s Teton Cougar Project, dispersed from their mother’s home range in northwest Wyoming, about April 1st, 2014, when the pair were 19 months old. In northern climates, there is a Spring pulse of young mountain lions setting out to find territories of their own. M80 moved north in one decisive movement, never to return. His sister, F96, was more tentative. Several times, she looped away from her mother and then back again. Upon returning from an exploratory adventure, F96 would find her mother and feast upon her kills. Finally, F96 moved south following the mountains forming the eastern edge of the vast valley called Jackson Hole.
In terms of biology, dispersal is an individual’s one-way ticket away from the area where the animal was born and raised by their mother, or in some cases, their mother and father. Mountain lion dispersal is one of the least known aspects of their ecology, as dispersal is particularly difficult to study in wide-ranging, secretive species. Research suggests that male mountain lions innately disperse to avoid inbreeding with their sisters and mothers. Not only do male kittens disperse more frequently than their sisters, but in general, much further as well. M80 dispersed more than 250 miles in eight months, whereas his sister traveled but 15 miles in the same time frame.
There are several competing hypotheses as to which circumstances trigger dispersal in mountain lions: 1) the timing of female estrous, 2) female conservation of energy, and 3) parent-offspring conflict. The first hypothesis predicts that dispersal occurs when females are receptive to mating, and that during estrous, females encourage their young from the previous litter to leave. We’ve seen no evidence to support the first hypothesis during Panthera’s 14-year Teton Cougar Project, but M80’s story, and the remainder of our work in northwest Wyoming, do support the second and third hypotheses.
Movie caption: F61, an adult female mountain lion (left), and her large kittens, M80 and F96 (lying in back). Watch M80 as he maneuvers in to displace his mother while she feeds. M80 breaks every rule of table etiquette, but as a teenager, he naturally pushes his boundaries. He successfully uses his bulk to get his way. Video by Mark Elbroch / Panthera
The second hypothesis predicts that kittens become competitors for their mothers time and energy as they become older—time and energy that their mother could instead be devoting to new pregnancies and rearing additional kittens. Looking back over the last three years, this is exactly what we’ve seen in three different litters. It would seem that kittens that disperse early, which we might define as before 18 months of age, is precipitated by pregnancy in their mothers. In all three cases in which females mated and became pregnant while still accompanied by kittens, the older kittens dispersed exactly one month before the birth of their mother’s next litter. These have resulted in particularly early dispersals as well. The average dispersal age for kittens in our study is 18 months, but in these instances, two litters dispersed when kittens were 14 months old, and one when the last remaining kitten was just 9 months old. In fact, F61 pushed out F97, her female offspring, and F88 her adopted offspring born to F51, when they were 14 months of age, just one month prior to giving birth to M80, F96, and their brother, M74. We caught great video of F61 and F97’s final days together. F61 continually hissed and swatted at F97, even while F97 made herself as small as possible and slept a safe distance away. She still hissed every time her daughter moved, or approached. It was the last time they were seen together before F97 dispersed west to the Teton Range.
The third hypothesis is that dispersal is prompted by parent-offspring conflict. Our remote camera research certainly supports this idea, and that the second and third hypotheses are not mutually exclusive. Parent-offspring conflict triggered dispersal in the remaining three litters we’ve followed over the last three years when the kittens were between 18-20 months of age. Regardless of whether their mothers were pregnant and needed to create room for the next litter, females “encouraged” their young to set out on their own. They tended to do this by making their teenage kittens feel particularly unwelcome (meaning mothers act aggressively toward them).
But let’s not paint female mountain lions as momzillas that turn on their innocent babies when they are sick of them. Teenagers are teenagers, whether mountain lions or humans, and teenagers push boundaries. M80 more so than his sister pushed the boundaries of mountain lion etiquette with his mother. By 16 months, he was considerably larger than his mother, and he would strategically use his bulk to get his way (see video above and photos below).
Mountain lion table manners require that they eat at a suitable distance from one another. If the carcass is small, this means that mountain lions must take turns eating at the carcass, but if it is large, like an adult elk or moose, two and sometimes three mountain lions may feed at the same time. These rules are concrete. They cannot be broken. Any mountain lion that violates the rules of respectful distance between feeding mountain lions or moves too close to a mountain lion that is eating, will elicit hissing, swatting, and/or lunging. Feeding mountain lions react ferociously and with blinding speed.
M80, as he grew to outweigh his mother increasingly violated these rules. He would slowly slink into close proximity with his mother while she was feeding, pausing at regular intervals as if testing the waters for her response. When he had slithered in close enough, he’d throw his bulky hind end into a position separating his mother from her food, and then he’d cringe in place and await her wrath. Depending on her mood and how much she’d eaten, she might just walk away, or move off after a few perfunctory swats to remind M80 that he was living in her house. If she vocalized and swatted during his approach, he knew not to push her any further and he’d retreat to await his turn.
M80 used a similar strategy to steal his mother’s warm bed sites in winter, those valuable spots without any snow. Because she was not eating, he could walk right up to her without violating table etiquette, but then he’d lean his weight on her, slowly pushing her from the bed, until his bulk had completely replaced her. These episodes were often met with swats and hisses from his mother, and the occasional nip reminding him that he may be larger, but that he was still her son. He took any abuse she doled out without contest, and we never witnessed M80 acting aggressively or violently with his mother. When she’d given up on moving him, he’d settle into his final position for a nap. F96 never exhibited any of these behaviors and always waited patiently to feed at carcasses. At beds, rather than trying to displace her mother or brother, she’d curl her body around them, still benefiting from her family’s warmth.
M80 was killed on Thanksgiving weekend, 2014 near Butte, Montana. He would have been nearly 26 months old. We are still following M80’s sister, F96, where she now resides in her newly established home range. Join us on Facebook to receive updates about F96 and other cats.
Liberg, O. & von Schantz, T. 1985: Sex-biased philopatry and dispersal in birds and mammals: the Oedipus hypothesis. American Naturalist 126: 129-135.
Logan, K.A. & Sweanor, L.L. 2001: Desert puma – evolutionary ecology and conservation of an enduring carnivore. – Island Press, Washington, D.C., USA.
Logan, K.A. & Sweanor, L.L. 2010: Behaviour and social organization of a solitary carnivore.-In:Hornocker,M.&Negri, S. (Eds); Cougar ecology and conservation. University of Chicago Press, Chicago, Illinois, USA, pp. 105-117.
Stoner, D.C., M. L. Wolfe, C. Mecham, M. B. Mecham, S. L. Durham & David M. Choate. 2013. Dispersal behaviour of a polygynous carnivore: do cougars follow source-sink predictions? Wildlife Biology, 19:289-301.