Hunger and knowledge: foraging decisions in an uncertain and social world

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Even within seemingly homogeneous habitats there is a great deal of small-scale heterogeneity over time and space. Thus, as animals explore their environment, there is variation between individuals in encountering food, resulting in population-level individual differences in hunger and knowledge. This variation is often further magnified by intrinsic consistent differences in behaviour between individuals (frequently referred to as animal 'personality'), which can be driven by differences in genetics and development that are stable in adulthood. How individuals manage the balance between feeding and avoiding predation risk when they have limited information is a long-running question in understanding animal behaviour. The story becomes much more complicated when we consider that many animals, especially those that are prey to others, live in groups. Living together has benefits in avoiding predators and locating resources, in part because animals can share information and socially learn from one another; on the other hand, coordinating when and where to do particular behaviours becomes a new problem. When and how information is gained and socially transmitted, and how hunger affects decisions and social behaviour, have been studied extensively but separately from one another. In this project, for the first time we will bring these elements together to understand how hunger and information interact when animals make foraging decisions both individually and collectively.Our study will utilise the recent explosion of interest in decision making by animal groups across taxa and advances in state-of-the-art animal tracking computer vision software. We will address a range of unanswered questions regarding hunger and information in decision making: What are the relative contributions of, and interactions between, hunger and risk taking tendency in the acquisition of information? How do interactions between individuals within groups influence these processes and what is the consequence for how knowledge and food are distributed between individuals? What is the effect of mixing informed and naïve, and hungry and sated, individuals in a group, e.g. do naïve individuals follow and learn better from satiated rather than hungry informed individuals that are likely to leave them behind? Can leadership emerge from differences in hunger that are driven by social interactions? Can more effective foraging in groups be best explained by sharing of information or simply by the extra motivation of having a partner? The project has the potential to greatly increase our understanding of decision making and the factors important in individual variation in social animals. The experimental work will use small freshwater fish as a model system. Compared to studying more complex animals such as birds or primates, there are a number of advantages to studying fish. Information and hunger can be easily controlled, and the species to be used (three-spined sticklebacks and guppies) have 'fission-fusion' social systems where individuals change group membership often, allowing us to easily manipulate group composition. As decisions and information exchange are evident in changes in speed and direction in most fish species, state-of-the-art computer vision software that tracks each individual's position over time will be used to quantify individual decisions objectively. Moreover, fish show many of the cognitive abilities found in 'smarter' vertebrates, suggesting that our results may be applicable to other animals, even humans. In parallel with the behavioural experiments, we will create new models of animal groups that consider how decision-making occurs when individuals are able to learn about their environment. Developing the models alongside the experimental work will maximise our ability to fully understand the complex interactions expected in the real animals.