CONTRAFREELOADINGIN STARLINGS: TESTING THE INFORMATION HYPOTHESIS

Contrafreeloading (CFL) behaviour, in which animals forage persistently in patches that require effort to exploit when patches containing ad lib. food are easily available, seems to contradict the predictions of optimal foraging theory. However, it has been proposed that contrafreeloaders are in fact exploiting a hidden resource, namely information about patches that may be useful in future foraging attempts. We performed two experiments on starlings Stumus vulgaris to test this hypothesis by determining the circumstances in which CFL occurs and assessing whether any useful information is acquired by animals performing the behaviour. In accordance with previous results we found that CFL is reduced when foragers are previously deprived of food and also when there are means of gathering information aside from sampling (namely when patches that require effort to exploit can be visually inspected). We also found that useful information is acquired by birds that perform CFL, in that when subsequently tested in extinction with the best patch removed they reliably chose the patch that had been the second best. These results are consistent with the information gain hypothesis. However, birds with low levels of CFL did not perform discernably worse in this test of patch knowledge and experimental reductions in CFL achieved through deprivation treatments did not produce apparent reductions in useful information possessed.