Prey size mediates interference competition and predation dynamics in a large carnivore community
Interference competition among predators can strongly affect fitness and prey dynamics, yet its drivers are often unclear. Using 23 years of cougar predation data from Yellowstone National Park, this study shows that prey size has context‑dependent effects: larger prey reduce cougar kill frequency but increase the likelihood that wolves and bears locate and steal kills. As primary prey decline, cougars shift toward smaller prey with shorter handling times, reducing kleptoparasitism risk. These findings challenge expectations that interference competition intensifies when prey densities fall or competitor densities rise. Instead, predator and prey traits can dampen competitive pressures, supporting coexistence in complex carnivore communities.
Subject Tags
- Life Sciences
- Wildlife
Abstract
Direct competition for resources is especially fierce among predators, leading to disproportionately strong effects on fitness and functional roles. These competitive effects are exacerbated in complex predator guilds with dominance hierarchies that have clear winners and losers. The direct costs of losing these competitions are well understood, but the drivers of such interactions, and their indirect effects on prey, are not. We evaluate the drivers of interference competition for cougars, and how such competition affects cougar-prey dynamics, by leveraging 23 years of cougar predation data from Yellowstone National Park, USA. We show that the effect of prey size is context-dependent, negatively affecting how often cougars kill ungulate prey but positively affecting how often wolves/bears find and steal cougar kills. Further, cougars increasingly kill smaller prey as larger, primary prey density decreases. Handling time is shorter for smaller prey, leading to less kleptoparasitism by wolves and bears when primary prey density is lower. Our study counters the theory suggesting that interference competition should increase at kills when prey density declines, interspecific competitor density increases, or kill rates increase. We demonstrate that predator, competitor, and prey traits drive the strength of and even dampen interference competition, possibly increasing coexistence in complex communities.
Citation
Rabe, J. W., Binder, W. J., Anton, C. B., Meyer, C. J., Metz, M. C., Smith, B. J., ... & Stahler, D. R. (2025). Prey size mediates interference competition and predation dynamics in a large carnivore community. Communications biology, 8(1), 424. https://doi.org/10.1038/s42003-025-07779-5
TNC Authors
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Toni K. Ruth
Idaho Riparian Restoration Project Manager
The Nature Conservancy
Email: toni.ruth@tnc.org