State-behaviour feedbacks between boldness and food intake shape escape responses in fish (Gasterosteus aculeatus)

Consistent differences in intrinsic state, amplified through state-dependent behaviour, could explain the ubiquity of animal personality variation. Boldness is often positively associated with a high metabolism and food intake. Even though a high food consumption is known to compromise oxygen-demanding activities, the influence of food intake on anti-predator escape responses has rarely been considered. By conducting experiments with three-spined sticklebacks (Gasterosteus aculeatus) in a setup with real-time tracking and a decoy heron predator, we show that bolder fish benefited from a higher food intake than shy fish, and reacted faster to a predator attack when food intake was the same before being attacked. However, a higher food intake slowed down the escape responses. These results shine light on how the fitness of shy and bold tactics could be balanced in the wild: the faster reaction of bold fish is impaired by their higher food consumption.