Altitudinal differences in foraging decisions under predation risk in great tits

Foraging decisions under risk of predation are crucial for survival as predation risk can contribute to a reduction of food intake over time leading to a trade-off between starvation and predation. Environmental variation can provoke changes in food accessibility or predation risk that will in turn affect foraging decisions. Specifically, less predictable or harsher environments, such as those found at high elevation, should lead to more risk-prone foraging in order to prevent risk of starvation, but empirical confirmation of this hypothesis is lacking. In the current study, we used video playbacks combined with an automatic feeder to measure continuous foraging choices between control and predator videos by wild great tits originating from high and low elevations and tested under controlled conditions. Great tits discriminated between two conditions representing differences in predation risk and visited the feeder less frequently when a predator was shown. Moreover, we found that birds from low elevation populations were more risk-averse and visited the feeder significantly less when a predator video playback was broadcasted compared with high elevation individuals. This elevation-related contrast was also dependent on the season, body mass, and fat reserves of individuals, and was more marked in females. Furthermore, adults visited the feeder less in the presence of a predator compared with yearlings. These results are consistent with predictions from life-history theory and starvation-predation trade-off hypotheses and could have implications for individual movements and population dynamics in changing environments. Foraging decisions based on the starvation-predation trade-off are influenced by environmental factors such as elevation. Under controlled conditions, we found that high elevation great tits are more risk-prone in foraging decisions compared with low elevation birds. Foraging decisions were also dependent on individual characteristics such as body mass, fat reserves, and age. Our results show that foraging decisions under predation risk vary among populations and could have important implications for population dynamics in changing environments.

Automated summary

Foraging decisions are influenced by predation risk and individual characteristics, and can have important implications for population dynamics.