Portal de Periódicos da CAPES

Pumas: solitary but social?

2017; Wiley; Volume: 15; Issue: 3 Linguagem: Inglês

10.1002/fee.1479

1540-9309

L. Mark Elbroch,

Primate Behavior and Ecology

On May 5, 2012, I captured my first video of an interaction between adult pumas (Puma concolor) in the Bridger-Teton National Forest east of Grand Teton National Park, an area where large ungulate prey are abundant but pumas live at lower densities than across most of the West (Quigley and Hornocker 2010). Location data collected by F57's collar (F denotes “female” and 57 is her unique id) revealed that she had remained in place for two full days, a behavior typically indicative of pumas that have made a kill. When new data conveyed that another puma – F109 – had closed to within 500 m of F57's position, I rushed out to set motion-triggered cameras over the elk (Cervus canadensis) carcass I discovered at F57's location. Three days later, I reviewed the video footage in the office of Panthera's Teton Cougar Project with anticipation – F109's data indicated that she had visited the kill. At precisely 11:35 pm on the date I set the camera, F57 trotted into frame under cover of darkness (WebVideo 1). She quickly backtracked and hissed loudly in the direction from which she had just come. F109 emerged on screen, walking stiff-legged and tall; F57 snarled and retreated to the left side of the carcass. F109 followed, closing the distance between them from nine meters to two. F57 instantly rolled onto her back, her four clawed feet aimed at the interloper. F109 hissed quietly, and then turned her head to the side, communicating mild submission. Something was settled in the quiet moments that followed, for the pair shared the kill for the next day and a half, often feeding together from opposite ends of the carcass (WebVideo 2). F57's 6-month-old kitten and F109's two 8-month-old kittens moved like satellites around them, feeding only when their respective mothers were alone at the kill or when neither adult was present. Pumas are solitary carnivores. In fact, 35 of the 37 wild felids are described as solitary, a life-history strategy characteristic of species living in complex habitats where predators compete for dispersed prey (Sandell 1989; Logan and Sweanor 2001). Theory suggests that, when stalking across leaf litter and twigs, one puma has a much better chance of capturing prey than do four pumas making four times the noise. But solitary is not equivalent to non-social (Leyhausen 1979). Instead, solitary behavior among carnivores is described as the antithesis of cooperative behavior: solitary carnivores do not cooperatively raise young, forage, attract mates, or defend resources from competitors or predators (Sandell 1989). Solitary carnivores are expected to interact infrequently, and these rare interactions can be explained by courtship or territorial disputes (Logan and Sweanor 2001). Perhaps, then, the prolonged interaction between F57 and F109 was an anomaly? Fortunately, and unexpectedly, our team continued to document social interactions among pumas. Indeed, when we combined interactions determined through simultaneous location data and additional interactions caught on motion-triggered cameras placed at puma kills, we discovered that each adult puma in our study area was interacting with other adult pumas at least 26 times per year (Elbroch and Quigley 2016). We also documented three adult pumas together on six different occasions. In the first two instances, an adult male fed with two females and their four kittens that he sired (seven pumas total). In the third, an adult male fed with two females and their four unrelated kittens (seven pumas total). In the fourth, a courting pair fed with another adult female; neither female had kittens at the time. In the fifth, three adult females without kittens fed together. And last, we watched two adult females alternately breed with a resident male, while the waiting female lay nearby. At kill sites, we have recorded puma aggregations numbering as high as nine individuals, including kittens. Sixty percent of adult interactions in our study area occurred at kills made by one of the interacting pair (Figure 1). We call this “conspecific tolerance”. It makes sense for carnivores to tolerate conspecifics when their prey is so large that the costs of tolerating another animal sharing the kill are much less than the potential costs associated with fighting and being injured (Macdonald 1983). Many suspect this sort of tolerance is explained by kinship theory, which predicts that animals that tolerate their relatives are actually investing in their own genetic lineage, thus diminishing the costs associated with the behavior (Hamilton 1963; Macdonald 1983). So, perhaps F57 and F109 were related? The answer to this question is no, based on genetic samples gathered during capture events and parent–offspring lineages (Elbroch et al. 2014). One might suspect, then, that pumas are not solitary at all. However, an average of twenty-six interactions between adult pumas per year is in fact a tiny number when considering the number of days in a year that animals could interact. Let us review solitary behavior as presented above: (1) We did not document cooperative foraging or hunting. (2) We did not document cooperative mating strategies; however, we did watch two females breeding with a single male. Nevertheless, the females did not appear to be working together to court the male, but rather were apparently exhibiting tolerance of a conspecific at a shared “resource” (a breeding-age male). (3) We did not document pumas cooperatively defending resources. (4) But did we document pumas cooperatively raising their offspring? Perhaps. When an adult puma kills prey and subsequently exhibits tolerance of an unrelated female with kittens scavenging at his or her kill, has that individual contributed enough energy to the unrelated offspring to provide some fitness advantage? Maybe, but a single occurrence of tolerance is insufficient support for this line of reasoning. Still, repeated tolerance of conspecifics with young at another's kills may indeed indicate that pumas practice cooperative provisioning of offspring. Tolerance among pumas at their kills is a fascinating behavior and deserves further research (WebVideo 3). For example, does tolerance vary with prey size? If there is a threshold prey size below which tolerance does not occur, we might be able to predict the frequency of social interactions in systems with different prey assemblages (eg fewer interactions in deer–raccoon systems in suburbia versus more in moose–elk–deer systems in the Northern Rockies). Further, if tolerance occurs only at large carcasses, reciprocal tolerance among pumas might be a strategic foraging strategy wherever pumas expend substantial energy to kill prey many times their size. Tolerance may also vary with puma density or prey availability. Pumas are a cryptic species and are difficult to observe in the wild. Nevertheless, I suspect that the pumas in our study area are no different from other populations and that clandestine social interactions occur between pumas wherever they live. When I sifted through the gray and scientific literature, I found evidence that tigers (Panthera tigris), leopards (Panthera pardus), and jaguars (Panthera onca), which are also solitary, territorial species, sometimes aggregate at kills made by conspecifics for short periods (Schaller 1967; Caro 1989; Guilder et al. 2015). Conspecific tolerance among solitary carnivores might be widespread at food resources (Figure 2), and technologies such as GPS collars and motion-triggered cameras may be revealing what has been occurring all along. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.