Contrasting properties of predation and scavenging networks governed by megaherbivores in an African savannah.

Predation and scavenging are two faces of carnivory that operate under distinct ecological rules, yet food web research often overlooks this distinction by ignoring scavenging or conflating it with predation. Using an 8-year dataset of mammalian carnivore feeding events from the Maasai Mara (Kenya), we explicitly separated predation and scavenging to compare their network structure. The study system includes a diverse carnivore guild and a broad herbivore prey size spectrum, including megaherbivores (>1 ton). We assessed two network properties (nestedness and modularity), identified species contributions to network structure and examined the relationships between these species-level contributions and body mass, between the number of interaction events per link and prey/carcass body mass, and between consumer and resource body mass. Despite largely involving the same species, the two networks differed markedly: both were nested, but only the predation network was modular, with modules aligned with prey size classes. As expected, body-size asymmetries structured the two networks in contrasting ways: predation was mostly limited to prey of similar or smaller size than the predator, with a sharp decline above the megaherbivore threshold, whereas larger carcasses, especially those of megaherbivores, attracted more scavenger species. The most influential species across metrics and network types was a herbivore, particularly the wildebeest, except for the lion in weighted nestedness within the predation network. These species-level contributions to network structure were unrelated to body mass. Relationships between consumption degree and prey/carcass body mass differed between networks, and predator-prey body mass correlated positively, unlike scavenger-carcass body mass. These asymmetries reveal opposing size-based constraints, with predation being more tightly constrained by body size than scavenging. Although similar patterns have been suggested previously, no study has directly compared both networks within the same system. Overall, our results show that predation and scavenging are complementary, not functionally redundant, components of carnivory food webs. We also propose a scalable framework for cross-ecosystem comparisons of species-level differences in network structure. Distinguishing scavenging from predation is essential to fully reveal the true architecture of food webs and the mechanisms governing energy flow through ecosystems.