Mammalian carnivores exclude or suppress their competitors even when diet overlap is minimal. On average, top predators have a disproportionate (~4-fold) effect on their competitors; this suppression occurs primarily through interference competition (direct aggressive interactions), as well as the avoidance response that displaces subordinate species from large portions of the landscape. African lions are often cited as a primary driving factor in suppressing cheetah populations. Although they have limited diet overlap, lions kill ~70% of cheetah cubs and steal food from cheetahs whenever possible; across African wildlife reserves, higher lion densities predict fewer cheetahs. However, recent population analyses from Serengeti National Park, Tanzania, indicate that cheetahs continue to coexist with lions despite dramatic increases in lion populations, whereas wild dogs disappeared. Here we quantify the joint population dynamics between lions and cheetahs, and the role of spatiotemporal partitioning as a mechanism for coexistence. Lion and cheetah population sizes have been simultaneously measured in Serengeti for >30 years, radio-telemetry data were collected on both species between 1985 and 1991, and a large-scale camera-trap survey (225 cameras across >1,000km2) was initiated in 2010 to collect spatiotemporal patterns of habitat use by cheetahs in the long-term lion study area where 24 prides are currently monitored by radio-telemetry.
Results/Conclusions
In contrast to dramatic declines by African wild dogs in the Serengeti plains as the lion population increased three-fold between 1966 and 1991, lion and cheetah population sizes were positively correlated between 1981 and 2010. Home range analysis of the lion/cheetah radio-tracking data show that the two species occupied similar areas across a 2,000 km2 region of the Serengeti. The camera trap survey confirms that cheetahs are more likely to range within lion territories than expected by chance, but when ranging inside lion core areas, cheetahs increase their use of open habitat.
Dominant predators can significantly reduce populations of subordinate competitors by displacing them from large portions of their habitat. Our results suggest that subordinate competitors may not be significantly suppressed if they are able to achieve fine-scale avoidance, which reduces their effective habitat loss. The efficacy of such fine-scale avoidance may depend on habitat structure or heterogeneity. Understanding how avoidance behavior and habitat characteristics interact to drive coexistence can inform predator reintroductions in ecosystems around the world.