Sandeels increase reliance on social cues when private information is uncertain

Abstract

Many animals must decide when and where to forage with only limited information about the profitability of food patches. To reduce uncertainty, animals can sample information about patch profitability from private or social information, with individuals adapting their foraging decisions based on the availability and reliability of those cues. Here, we investigated how the lesser sandeel, Ammodytes tobianus, a schooling, semipelagic fish, integrates private information and social cues when emerging from the sand and entering the water column to feed. When food availability was certain, individuals emerged from the sand and entered the water column to feed, with individuals making faster decisions compared to when food availability was uncertain. When food availability was uncertain, however, sandeels were more likely to be found in a partially emerged state (with their heads protruding above the sand), with decisions about whether to enter the water column taking longer to make. Social cues, in the form of the number of individuals swimming in the water column, increased the likelihood of individuals deciding to swim, but only when food availability was uncertain. Together, these results suggest that sandeels adjust their use of private information and social cues to inform their decisions, with longer decision times and an increased likelihood of joining others when there is uncertainty about food availability in foraging patches.