Mesocarnivore community structuring in the presence of Africa's apex predator

Abstract

Apex predator reintroductions have proliferated across southern Africa, yet their ecological effects and proposed umbrella benefits of associated management lack empirical evaluations. Despite a rich theory on top-down ecosystem regulation via mesopredator suppression, a knowledge gap exists relating to the influence of lions ( Panthera leo ) over Africa's diverse mesocarnivore (less than 20 kg) communities. We investigate how geographical variation in mesocarnivore community richness and occupancy across South African reserves is associated with the presence of lions. An interesting duality emerged: lion reserves held more mesocarnivore-rich communities, yet mesocarnivore occupancy rates and evenness-weighted diversity were lower in the presence of lions. Human population density in the reserve surroundings had a similarly ubiquitous negative effect on mesocarnivore occupancy. The positive association between species richness and lion presence corroborated the umbrella species concept but translated into small differences in community size. Distributional contractions of mesocarnivore species within lion reserves, and potentially corresponding numerical reductions, suggest within-community mesopredator suppression by lions, probably as a result of lethal encounters and responses to a landscape of fear. Our findings offer empirical support for the theoretical understanding of processes underpinning carnivore community assembly and are of conservation relevance under current large-predator orientated management and conservation paradigms.

Broad aggressive interactions among African carnivores suggest intraguild killing is driven by more than competition

“…The fact that several African carnivores were involved in IGK events as both the aggressor and the victim challenges the classic two‐rank view on mesopredator suppression (Prugh et al 2009) and lends further support to potential multilevel cascading effects in species‐rich carnivore guilds (Levi and Wilmers 2012). In addition, the observed prevalence of large‐to‐small IGK events expands the multilevel theory by suggesting possibly stronger than predicted net suppressive effects of large carnivores, as highlighted by Prugh and Sivy (2020) and suggested empirically for lion suppression of African mesocarnivore species (Curveira‐Santos et al 2021 b ). We encourage future research that revisits top‐down structuring of carnivore guilds in other species‐rich systems containing large hyperpredatory carnivores (e.g., tiger [ Panthera tigris ] and leopard in Southern Asia or jaguars [ Panthera onca ] and pumas [ Panthera concolor ] in South America).…”

Context‐dependency in carnivore co‐occurrence across a multi‐use conservation landscape

“…However, particularly in the protected area, small carnivore species tended to spatially avoid lions. This is in line the with recently uncovered susceptibility of small African carnivores to lion suppression (Curveira‐Santos et al, 2022 ; Curveira‐Santos, Sutherland, Tenan, et al, 2021b ). Unlike larger subordinate species, better equipped to escape and mitigate dangerous encounters while co‐occurring with the apex predator, for small carnivores spatial avoidance of lions may be a better strategy (Wirsing et al, 2010 ).…”

“…Changes in guild composition are accompanied by varying levels of human disturbance and its influence on resource availability across multiple land uses. Together, these can deeply shape the structure of carnivore assemblages (Curveira‐Santos, Sutherland, Tenan, et al, 2021b ; Schuette et al, 2013 ) and potentially alter the underlying network of species interactions and community regulation pathways (Dorresteijn et al, 2015 ). Nonetheless, context‐dependent changes in carnivore assemblages have received little attention in carnivore‐rich regions of southern Africa, where context‐dependency is likely to have profound effects.…”

Occupancy winners in tropical protected forests: a pantropical analysis

“…The few studies that have assessed spatial patterns of such functional traits in tropical regions concluded that the functional composition of tropical forest mammals is largely consistent among regions, likely due to the age and stability of these forests, as well as similarities in climate and day length [ 4 , 7 ]. These studies, used species richness to determine functional composition and diversity [ 8 , 9 ] rather than ‘occupancy’—defined as the proportion of sites occupied by a species [ 10 ].…”