Explaining the survival of the sickest: altered walking patterns are linked with improved adult survival in Drosophila melanogaster grown with predators during larval development

Stress caused by predator exposure can lead to various behavioural, physiological, stoichiometric, and biochemical changes in prey. Prior research has shown that growth under predation stress can cause the development of a diabetes-like biochemical phenotype in fruit flies. Exposure to predator risk during larval development decreases flies’ walking activity, improving their antipredator strategies. However, it is unclear which elements of walking behaviour make flies less conspicuous to predators. This study shows that fruit flies (N = 729) grown with spiders walk shorter distances, accelerate faster and spend more time in a state of motion without movement (i.e., stomping in place) than control flies (N = 839). Under predation risk, adult flies grown with spiders survived better than control flies. We suggest that motions without movement may resemble sickness behaviour for predators, which we propose as the main reason for their better survival under direct exposure to predator attacks.