Repeated environmental change mitigates inter-individual inequal food gain in a group foraging experiment of crow

Animal group foraging produces unequal distributions of food gains among participants because of individual differences, such as dominance rank. However, external environmental factors, such as fluctuation of food spatial distribution over time, may mitigate the impact of social features on food acquisition. Earlier experimental studies focused on a group’s internal environment or were conducted in stable and unchanging environments. Here, we investigated how environmental fluctuations affect food acquisition at group and individual levels in captive large-billed crows ( Corvus macrorhynchos ) by changing the relationship between feeding sites and food quantity. We found that foraging efficiency and food distribution equality initially declined after environmental changes, gradually increased, and improved with repeated long-term environmental fluctuations. The influence of sex was found, while that of dominance rank was not. The present results provide the first experimental evidence to suggests that environmental fluctuations mitigate inequal food gain among individuals in group foraging.