Spatial associations in a solitary predator: using genetic tools and GPS technology to assess cougar social organization in the Southern Yellowstone Ecosystem

Abstract

We employed global positioning system (GPS) locations of 18 marked cougars and genetic material from 68 cougars in the Southern Yellowstone Ecosystem to test our current assumptions about the social organization of this non-cooperative, solitary carnivore. We tested whether variable numbers of spatial associations over 7 years of our project could be explained by increasing numbers of wolves in the system, decreasing numbers of prey, changes in cougar density, the mean genetic relatedness between interacting individuals, or the timing of the breeding season. We documented 92 spatial associations and an additional 190 incidents of spatial overlap. Our models suggested only season influenced the number of associations in any given year, and a greater frequency of associations occurred in the breeding season. Nevertheless, the proportion of associations that were male–female (M–F) remained consistent across breeding and non-breeding seasons, suggesting M–F associations may not entirely be driven by mating opportunities; alternatively, the frequency of associations may have been driven by snow depths and the distributions of cougar prey in winter. The mean r value for female–female spatial associations was 0.087 (defined as “unrelated”) and did not significantly differ from M–F or M–M associations. In conclusion, our genetic research revealed not only matrilineal lines in the Southern Yellowstone Ecosystem but also immigration by new females. Subadult males primarily emigrated out of the system, but one male remained philopatric. Our results highlighted the notion that solitary cougars are associating, and potentially interacting, on the landscape with regularity and predictability. Further, our results raised critical questions: If cougars are associating more frequently than previously believed, why do they do so and are these interactions typically agonistic?