An experimental test of optimal sampling behaviour in Siberian jays (Perisoreus infaustus)
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- Institutt for biologi 
Optimal foraging models tend to assume that animals have perfect information. However, the world is constantly changing, and so it is likely that animals benefit from gathering better knowledge much of the time. Therefore, animals should exploit what they know to be the most profitable foraging options, but also invest some optimal level of effort in sampling. Sampling is when an animal investigates alternative foraging options in order to find out which is the best one to utilize at the current time. The aim of this study was to investigate if the Siberian jays (Perisoreus infaustus) used sampling and public information to exploit the best combination of different foraging patches of variable profitability. This was done using an experimental feeding platform containing a number of different randomly arranged patches each consisting of four closely spaced colour-coded tubes (i.e. one-shot feeders), each containing the same of one of five different sizes of food items (sausage pieces). Overall, the jays exploited significantly more tubes in patches that contained large sausage items than would be expected at random. This foraging success better than chance was achieved using a long-term approximation of the win-stay lose-shift strategy i.e. the birds used information provided by a tube to either come back to the same patch again if a large item was obtained ( success ), or shift to sample a new patch if a small item was obtained ( no success ). Hence, if a tube with large item was opened, the birds were more likely to return to this patch again. However, they did not always return immediately since no significant influence of the previous success was found, suggesting a longer-term strategy involving more than one patch at a time. In addition, the birds opened significantly more tubes containing large items than chance when visiting new patches that other birds had already visited, suggesting some use of public as well as private information. It therefore seems that Siberian jays try to maximize their food intake over the whole trial period and not just per visit. They do this by deviating from a simple win-stay lose-shift strategy, keeping the profitability of more than just two patches in mind at any one time and by exploiting the public information provided by the sampling behaviour of other birds.