Cofeeding at rich clumped food patches in free-ranging dogs: social tolerance or scramble competition?

Animals are generally expected to monopolize food patches whenever possible. However, cofeeding within a defendable range occurs in many species, particularly at larger food patches, but the mechanism behind that remains underexplored. In theory, it could be due to multiple, mutually non-exclusive processes. First, larger food patches may saturate multiple top-ranking individuals, enabling cofeeding even under pure contest competition. Second, cofeeding may result from social tolerance where dominant individuals provide cofeeding concessions to certain subordinates. Third, cofeeding may result from prevailing scramble competition (i.e., indirect competition through patch exploitation) caused by large numbers of individuals that prevent monopolization ("swamping"). To investigate and differentiate between these mechanisms, we applied feeding tests to free-ranging dogs in Morocco. We provided them with a large food patch plus a varying number of small food patches. Although the small food patches were virtually always monopolized by single individuals, the dogs typically cofed in large and very dense feeding groups at the large food patches. Controlling for alternative explanations using multivariate statistics, we found that access to feeding groups was independently predicted by rank and social relationship strength, suggesting that contest competition and social tolerance play a role. However, aggression rates by top-rankers decreased with increasing feeding group size, suggesting decreasing monopolizability and increasing scramble competition. Our results underscore that social tolerance may not reduce competition but shifts it from contest to scramble competition. This can be due to active levelling, licensing more individuals access to the resource, but also to loss of control caused by swamping.