Ecological traits and the spatial structure of competitive coexistence among carnivores

Competition is a widespread interaction among carnivores, ultimately
manifested through one or more dimensions of the species’ ecological
niche. One of the most explicit manifestations of competitive interactions
regards spatial displacement. Its interpretation under a theoretical
context provides an important tool to deepen our understanding of
biological systems and communities, but also for wildlife management and
conservation. We used Bayesian multi-species occupancy models on camera
trapping data from multiple sites in Southwestern Europe (SWE) to
investigate competitive interactions within a carnivore guild, and to
evaluate how species' ecological traits are shaping coexistence
patterns. Seventeen out of 26 pairwise interactions departed from a
hypothesis of independent occurrence, with spatial association being twice
as frequent as avoidance. Association behaviours were only detected among
mesocarnivores, while avoidance mainly involved mesocarnivores avoiding
the apex predator (n=4) and mesocarnivore-only interactions (n=2). Body
mass ratios, defined as the dominant over the subordinate species body
mass, revealed an important negative effect (β ̂=-0.38
[〖CI〗_95=-0.81,-0.06]) on co-occurrence probability, and support that
spatially-explicit competitive interactions are mostly expressed by larger
species able to dominate over smaller ones, with a threshold in body mass
ratios of ca. 4, above which local-scale intraguild coexistence is
unlikely. We found a weak relationship between pairwise trophic niche
overlap and the probability of coexistence (β ̂=-0.19
[〖CI〗_95=-0.58,0.21]), suggesting that competition for feeding resources
may not be a key driver of competition, at least at the scale of our
analysis. Despite local-scale avoidance, regional-scale coexistence
appears to be maintained by the spatial structuring of the competitive
environment. We provide evidence that SWE ecosystems consist of
spatially-structured competitive environments, and propose that
coexistence among near-sized species is likely achieved through the
interplay of “facultative” and “behavioral” character displacements.
Factors influencing carnivore coexistence likely include context-dependent
density and trait mediated-effects, which should be carefully considered
for a sound understanding of the mechanisms regulating these communities.