Competition structures ecological communities. In carnivorans, competitive interactions are disproportionately costly to subordinate carnivores who must account for the risk of interspecific killing when foraging. Accordingly, missed opportunity costs for meso-carnivores imposed by risk can benefit the smallest-bodied competitors. However, the extent to which the risk perpetuates into spatial partitioning in hierarchically structured communities remains unknown. To determine how risk-avoidance behaviors shape the space-use of carnivore communities, we studied a simple community of carnivores in northern Patagonia, Argentina: pumas (Puma concolor; an apex carnivore), culpeo foxes (Lycalopex culpaeus; a meso-carnivore), and chilla foxes (Lycalopex griseus; a small carnivore). We used multi-species occupancy models to quantify the space use within the carnivore community and giving-up densities to understand the behaviors that structure space use. Notably, we applied an analytical framework that tests whether the actual or perceived risk of predation most strongly influences the space use of subordinate carnivores although accounting for their foraging and vigilance behaviors. We found that there was a dominance hierarchy from the apex carnivore through the meso-carnivore to the subordinate small carnivore, which was reflected in space. Although both meso- and small carnivores exhibited similar predator avoidance behavioral responses to apex carnivores, the habitat associations of apex carnivores only altered meso-carnivore space use. The biases in risk management we observed for meso-carnivores likely translates into stable co-existence of this community of competing carnivores. We believe our analytical framework can be extended to other communities to quantify the spatial-behavioral tradeoffs of risk.

The return of large carnivores is predicted to suppress meso-carnivores, though it has only been observed in a minority of contemporary studies. Isle Royale is a remote island wilderness in Lake Superior, USA, managed for outdoor recreation. Following their natural extirpation, the National Parks Service translocated gray wolves (Canis lupus) in 2018–2019 and we expected the return of suppression and trophic facilitation of meso-carnivores. Nevertheless, we hypothesized that human resource subsidies led to a breakdown in meso-predator release. From Fall 2021-Winter 2024, we captured 16 individual red foxes (Vulpes vulpes), collected whiskers, and subsampled them to recreate the yearly diet of the population using stable isotope analysis. Notably, meso-carnivores were not demographically suppressed. Coinciding with the dates when Isle Royale National Park opened, fox diets were generalized, dissimilar between individuals, and primarily composed of human foods (0.28 ± 0.02) during summer. In winter, fox diets were specialized and exhibited high similarity, being composed primarily of carrion subsidized by wolves (0.62 ± 0.04). We propose that the complementarity of human resource subsidies to communities and ecosystems, broadly, may help explain the limited reach of the anticipated interactions following the return of large carnivores, such as meso-predator release.

The repatriation of species is common, especially in conservation efforts aimed at restoring trophic interactions. Whether the Eltonian niches of restored species are conserved in reassembled ecological communities is largely unknown. Within mammalian carnivores, we hypothesized that the Eltonian niches of sympatric competitors would be structured by trophic facilitation from subsidies provided by large carnivores (i.e. carrion) and humans (i.e. food subsidies). Using stable isotopes (δ¹³C, δ¹⁵N), we quantified the Eltonian niches of an apex predator, the grey wolf Canis lupus and two subordinate guild members, coyotes Canis latrans and red foxes Vulpes vulpes, from Michigan, USA across three periods that differed in community composition: a ‘historical' carnivore community (1910–1930), a ‘reduced' community which lacked wolves (1950–1970), and a ‘reassembled' carnivore community featuring wolves as well as human food subsidies (2000–2020). In historical and reassembled communities, wolves constrained the niche space of coyotes via resource facilitation, regardless of human presence, such that the consumption of deer by coyotes increased by an average of 1.4–1.8‐fold in the presence of wolves. Without wolves, coyotes exhibited an isotopic (dietary) niche breadth ~ 2–5× greater (3.33 ± 0.74‰²) than in the historical (0.64 ± 0.11‰²) and reassembled (1.66 ± 0.63‰²) communities. Conversely, we found that the niche breadth of foxes was conserved across the historical (1.91 ± 0.41‰²) and reduced (1.98 ± 0.75‰²) communities but increased ~ 4‐fold in the presence of human resource subsidies (7.52 ± 1.95‰²). Notably, we found that trophic facilitation by wolves and resource subsidies from humans altered the foraging strategies of individuals, resulting in disparate foraging strategies for foxes in the reassembled community. Our results highlight that Eltonian niche conservatism in carnivore communities is driven by resource subsidies, both from the provisioning of carrion by large carnivores to meso‐carnivores and from human foods subsidizing small carnivores. More broadly, our work suggests that large carnivore repatriation can restore some species interactions, while human resource subsidies can decouple others.