Spatial scale mediates carnivore coexistence in a ‘landscape of fear’

Background/Question/Methods

Predators can affect prey populations by stimulating costly defense strategies (trait mediated indirect interactions, or TMIIs). Meta-analyses indicate these behavioral responses can have greater demographic impacts on prey populations than direct mortality, even triggering cascading effects across trophic levels. However, despite significant research examining the role of TMIIs in predator-prey coexistence, the role of TMIIs in driving intraguild predator-predator coexistence is largely unexamined. Here we examine how aggressive interactions create a “landscape of fear” within a guild of African predators, and the implications of this landscape for intraguild predator coexistence. We first compare joint population dynamics of lions, cheetahs, and African wild dogs using 40 years of time-series data from Serengeti National Park. We then examine patterns of habitat use across a range of spatial scales for evidence of displacement of cheetahs and wild dogs from preferred habitats, using a combination of citizen-science-processed camera-trap data (200 single-camera stations across >1,000km²), and radio-telemetry locations for lions and cheetahs (concurrently tracked 1985-1990). Finally, we cross-validate our results from the Serengeti with data on coexistence between lions, cheetahs and wild dogs following reintroduction programs in 30 private game reserves in South Africa.

Results/Conclusions

Our results demonstrate radically different responses of subordinate species in both temporal population trends and spatial habitat use, highlighting the importance of TMIIs in driving intraguild predator coexistence. The Serengeti lion population increased nearly three-fold between 1966 and 1998, likely contributing to the elimination African wild dogs but having no apparent effect on cheetah numbers. Wild dogs were lower in years of high lion density (p<0.0001, r²=0.63), while cheetah numbers were unrelated (p=0.19, r-sq=0.09). Whereas wild dogs show large-scale avoidance of lions, cheetahs do not succumb to displacement from preferred habitats. Notably, cheetahs were positively spatially correlated with lions across the study area (p<0.0001) and instead demonstrate fine-scale habitat partitioning while inside lion territories, increasing their use of more open habitats. Similarly, across South Africa, wild dog densities were lower in reserves with more lions, while cheetah numbers were unrelated. These findings suggest that while TMIIs can result in large-scale displacement of subordinates from preferred habitats, fine-scale partitioning facilitates coexistence by minimizing displacement and associated habitat-loss. Examining landscape partitioning across spatial scales in other systems with and without suppression would provide a more comprehensive understanding of how avoidance behavior and habitat characteristics interact to promote species coexistence.