Contrafreeloading in starlings: Testing the information hypothesis

Contrafreeloading (CFL) behaviour, in which animals forage persistently in patches that require effort to exploit when patches containing nd lib. food are easily available, seems to contradict the predictions of optimal forag ing theory. However, it has been proposed that contrafreeloaders are in fac t exploiting a hidden resource, namely information about parches that may b e useful in future foraging attempts. We performed two experiments on starl ings Sturnus vulgaris to test this hypothesis by determining the circumstan ces in which CFL occurs and assessing whether any useful information is acq uired by animals performing the behaviour. In accordance with previous resu lts we found that CFL is reduced when foragers are previously deprived of f ood and also when there are means of gathering information aside from sampl ing (namely when patches that require effort to exploit can be visually ins pected). We also found that useful information is acquired by birds that pe rform CFL, in that when subsequently rested in extinction with the best pat ch removed they reliably chose the patch that had been the second best. The se results are consistent with the information gain hypothesis. However, bi rds with low levels of CFL did not perform discernably worse in this test o f patch knowledge and experimental reductions in CFL achieved through depri vation treatments did not produce apparent reductions in useful information possessed.