Social foragers rely more on dynamic cues than prior beliefs in unpredictable natural environments
Foraging is a prime example of adaptive decision-making in uncertain and changing environments. Foragers need to continuously integrate their direct experiences and observations of what others are doing with what they already know about the distribution of prey. Yet little is known about the importance of prior knowledge relative to dynamically sampled information in social foraging settings. Here, we investigated the role of prior beliefs in five large-scale ice-fishing competitions involving 49--53 highly experienced ice-fishers in 251 foraging trips. To quantify their prior spatial beliefs, participants marked areas they believed to have high resource abundance on topographic maps containing isoclines (i.e., depth curves) before each competition. GPS devices and headcams tracked behavioural states and foraging success. We found that prior beliefs about the fish distribution are to a large extent driven by lake topography and therefore converge across individuals. However, these prior beliefs were not systematically linked to foraging success. While prior beliefs predicted spot choices, especially in the beginning of competitions, they were heavily outweighed by dynamic personal and social information sources. Exploring how the use of prior beliefs differed between foraging trips, we found that high reliance on prior beliefs was associated with reduced avoidance of unsuccessful locations which resulted in limited spatial exploration. We conclude that dynamic information sampling and accumulation are key processes in social foraging decisions, with prior spatial beliefs playing only a minor role in natural environments where resources are hard to predict in advance.