Résumé
The ratio of predator-to-prey biomass density is not constant along ecological gradients: denser ecosystems tend to have fewer predators per prey, following a scaling relation known as the 'predator–prey power law'. The origin of this surprisingly general pattern, particularly its connection with environmental factors and predator–prey dynamics, is unknown, but has been proposed to be explainable through density-dependent interactions among prey (what we call a bottom–up origin). In contrast, we combine two complementary theoretical approaches to demonstrate how sublinear predator–prey scaling can also emerge from density-dependent interactions among predators and between predators and prey (a top–down origin). First, we use phenomenological differential equations to explore the role of environmental parameters and dynamical properties behind the predator–prey ratio. Second, we simulate an agent-based model with tunable predator self-regulation to investigate the emergence of predator–prey scaling from plausible microscopic rules. While we cannot rule out alternative explanations, our results show that density-dependent mechanisms relative to predation and intraspecific predator interactions, including prey saturation, predator interference, and predator self-regulation, offer potential explanations for the predator–prey power law.