Context Dependent Effects of Large Carnivores on Mesocarnivores: Pumas and Foxes in Patagonia

Abstract

Large carnivores often structure mesocarnivore communities through strong negative suppressive effects such as killing, predation, and resulting fear. However, it is increasingly apparent that ecological context can strongly influence the nature and strength of these large carnivore effects. Research assessing variability of interactions among carnivores remains limited, especially within the same community in different contexts. To better understand this variation, we quantified the spatial and temporal response of South American foxes (Lycalopex griseus and Lycalopex culpaeus) to puma (Puma concolor) presence and provisioning of guanaco (Lama guanicoe) carrion in Monte León National Park and Parque Patagonia, Argentina. We built models of puma space use and guanaco killsite location in each site utilizing movement data from puma GPS collars and GPS cluster investigation data, respectively. We integrated these models with trail camera data as detection covariates in occupancy models for foxes. Despite both sites being a steppe ecosystem and having identical carnivore and similar terrestrial vertebrate communities, we found patterns of puma space use and hunting varied between sites. These differences created different landscapes of risk (puma use) and reward (guanaco carrion), which drove different spatio-temporal responses of foxes. In Monte León, where pumas were concentrated, predictable, and risk and reward were correlated, foxes showed

strong spatial avoidance of pumas and their hunting areas. In Parque Patagonia, where pumas were dispersed, unpredictable, and risk and reward were largely uncorrelated, foxes showed only weak temporal avoidance and of pumas and hunting areas. This difference in puma behavior and fox response appears to be the result of geography and a colony of Magellanic penguins (Spheniscus magellanicus) which concentrated high-densities of pumas into canyons in Monte León, conditions which were not present in Parque Patagonia where more complex terrain did not link pumas strongly to any geographic feature, leading to a more dispersed distribution. These results show the response of mesocarnivores to large carnivores is not fixed, but a dynamic response to myriad conditions that vary even between similar sites with the same carnivore community.