Individual willingness to leave a safe refuge and the trade-off between food and safety: a test with social fish.

Refuges offer prey animals protection from predation, but increased time spent hiding can reduce foraging opportunities. Within social groups, individuals vary in their refuge use and willingness to forage in the presence of a predator. Here, we examine the relative foraging benefits and mortality costs associated with individual refuge use and foraging behaviour within groups of goldfish (Carassius auratus) under predation risk from an avian predator (little egret-Egretta garzetta). We assessed individual order of emergence from the refuge and participation over 15 group foraging outings, and assigned each fish a daily outing index score. The individual fish that emerged from the refuge earlier than the other group members and that participated in more outings received high outing index scores and consumed more food compared with fish that tended to emerge in posterior positions and participate in fewer outings. However, individual fish that attained high outing index scores suffered a higher risk of predation. Furthermore, the amount of time the egret spent at the pool affected group foraging behaviour: as predation risk increased, groups of fish consumed significantly less food. Our results exemplify the trade-off between foraging success and safety from predation that prey species regularly experience.

State-dependent foraging among social fish in a risky environment.

In the presence of a predator, foraging is a dangerous task. Social individuals can respond to risk by forming groups, benefiting from enhanced collective anti-predator behavior but suffering from increased conspicuousness to predators. Within groups, individuals exhibit variable foraging behavior. One important factor influencing risky foraging behaviour is current energetic state, and individuals must trade off food and safety by deciding when to leave a protected refuge in order to find food. We generated mixed groups of goldfish (Carassius auratus) containing equal numbers of underfed and well-fed individuals and examined individual refuge use and willingness to take risks venturing into risky foraging areas in the presence of an avian predator (little egret-Egretta garzetta). Underfed fish exhibited higher levels of risky behaviour by participating in more foraging outings and emerging from the refuge in frontal group positions, compared with well-fed individuals. As expected, underfed fish benefitted by consuming more food, but surprisingly did not experience higher rates of mortality. This may be due to the fact that the egret predator rarely captured the first fish to emerge from the refuge, preferentially attacked groups of three or more fish, and often captured fish in the chaotic period following a failed initial strike. We demonstrate how differences in energetic condition can influence risk-taking behaviours among social individuals that subsequently influence relative levels of foraging success and group fission-fusion dynamics. Moreover, our results illustrate the risk associated with foraging in larger groups.

Identifying individual male reproductive consistency in Drosophila melanogaster: The importance of controlling female behaviour.

Work on the repeatability of reproductive behaviour has mainly focused on the consistency of female preferences. We characterised the consistency of individual male Drosophila melanogaster reproductive behaviour in two experiments. In the first experiment, we allowed males to interact with a pair of live females that differed in body size. We then controlled female behaviour in a second experiment by examining the courtship behaviour of individual males interacting with a pair of decapitated females that varied in body size. In both experiments, we examined the consistency of individual male reproductive behaviour across two repeated trials on the same day. Males did not exhibit a courtship preference for the larger female in either experiment, but, in experiment 1, males did exhibit post-copulatory choice by copulating for longer durations with the large female, and males that mated with the same type of female in both trials exhibited repeatable behaviour. In general, we found weak evidence of consistent male courtship behaviour in the presence of behaving females. However, when female behaviour was controlled in experiment 2, we found that male courtship behaviour was highly repeatable. These results indicate that individual male D. melanogaster exhibit consistent reproductive behaviour and demonstrate the importance of controlling female behaviour when attempting to characterise the repeatability of male reproductive behaviour.