Foraging behaviour in captive red knots: the role of individual differences in the use of social information
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Collective behaviour is widespread among animals, and through social learning, it provides individuals with ways to deal with rapid environmental change. Within the group, animals differ in personality and are engaged in networks of social interactions. The availability and spread of information about the location and quality of resource patches may depend on the distribution of personalities. Previous studies have found that individuals with exploratory personality are more likely to discover food patches; therefore, non-exploratory individuals could benefit from following explorers. Calidris canutus islandica are suitable candidates for using public information to increase their foraging success, and consequently survival rates, because the benefits outweigh the costs. In fact, knots benefit from sharing foraging information while avoiding costs of competition, as food is abundantly but cryptically dispersed on the mudflats. In this project, we investigate the use of social information by captive red knots, examining their foraging behaviour both alone and in the group. Several behavioural assays were conducted in the experimental shorebird facility at NIOZ (Texel, The Netherlands), where 21 patches were placed in a sandy arena, but only one contained prey items. Fifty captive red knots, whose exploratory personalities were previously assessed, were tested in this setup, firstly alone and subsequently in groups of 2, 3 and 4 total birds. For all trials, the fraction of time the focal bird took to discover the filled food patch was measured and identified as "searching time", which was analysed in relation to individual-level traits and group's characteristics. The results unexpectedly show that exploratory personality does not influence foraging behaviour in any case. Nevertheless, all the birds became faster in finding the food when they were in a group. Most importantly, non-exploratory birds remarkably benefit from being with other individuals that share information about the food patch location through local enhancement. This captivity study gave insights into the use of social information by knots and how their foraging behaviour changes from being alone to being in a group, highlighting the vital importance of group foraging, especially for non-exploratory individuals.