Nine-spined sticklebacks deploy a hill-climbing social learning strategy

Theoretical models on the adaptive advantages of social learning lead to the conclusion that copying cannot be indiscriminate and that individuals should adopt evolved behavioral strategies that dictate the circumstances under which they copy others and from whom they learn. Strategies that exhibit hill-climbing properties, that would allow a population of individuals to converge on the fitness-maximizing behavior over repeated learning events, are of particular significance due to their potentially critical role in cumulative cultural evolution. Here, we provide experimental evidence that nine-spined sticklebacks (Pungitius pungitius) use public information adaptively and in accordance with a hill-climbing social learning strategy. Sticklebacks switch patch preferences to exploit a more profitable food patch if the returns to demonstrator fish are greater than their own but are less likely to copy when low-profitability patches are demonstrated. These findings reinforce the argument that public-information use in nine-spined sticklebacks is an adaptive specialization. More generally, the observation of this sophisticated form of learning in a species of fish supports the view that the presence of enhanced social learning may be predicted better by specific sources of selection than by relatedness to humans.