Using real predators and robot prey to investigate the importance of predators in prey responses

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Predator and prey are locked in a dynamic interplay of evolved behaviour; predators attempt to maximise their net intake while unsuccessful prey do not live to see another day. This often culminates in dramatic behavioural displays, as cheetahs chase gazelles across the savannah, gannets dive bomb sardine shoals, and bats hunt moths through echolocation. However, while recording and analysing this is possible, studying this type of behaviour is problematic as ideally we would manipulate the response and movement of prey, which is technically very difficult. Without manipulation, it is difficult to say with any certainty that such behaviour has evolved to help animals avoid predation. This has limited our understanding of dynamic responses to predation as the behaviour of predators is often based on unsupported assumptions rather than empirical data. By using recent technological developments, this project will explore how short-term behavioural avoidance by prey has evolved to minimise risk, how predators learn to counteract these strategies, and whether this locks predator and prey into a cycle of adaptation and counter-adaptation.Predatory fish (the European perch, Perca fluviatilis) will be allowed to encounter, detect, attack and try to consume (i.e. 'kill') artificial robotic prey, small items of food magnetically connected to robots under the testing tank. While the predator's behaviour is unconstrained, the behaviour of the prey are under full control by a computer program. To allow responsive behaviour by the prey, the predatory fish will be tracked by a computer in real time and this information will be fed back and made available to the prey. The complexity of the prey's reaction will be manipulated, from relatively simple behaviours such as fleeing from the predator or aggregating toward other prey, to the more complex such as balancing aggregation with fleeing. In the latter stages of the project, the longer term dynamics of predator-prey interactions will be examined, where the frequency of different prey strategies will change over time based on the previous success of each strategy. This will simulate an evolutionary process and how the predators adapt their subsequent behaviour to these changes in prey strategies will allow an examination of the role of learning in these interactions.The main focus of interest will be on the responses of prey groups. These collectives (flocks, schools, herds, swarms) continue to fascinate scientists, filmmakers and the public alike. One shared reason is the almost incomprehensible degree of coordination between individuals in some of these species; the evening displays of European starlings (Sturnus vulgaris), for example, attract visitors to sites across the U.K. and is also the subject of a major European Commission research project. There is currently much research interest in these 'self-organised' systems across disciplines, including physics, computer science and engineering as well as biology, and there are applications in controlling pedestrian crowds and pest swarms such as locusts. The proposed method will allow us to examine with unprecedented detail how this group behaviour protects prey from predators. For example, it is often thought that polarisation (where individuals in groups line up to face the same direction) facilitates information transmission between individuals, as a response to detecting a predator or food source. By manipulating this behaviour, it can be tested whether this actually is effective at avoiding real predatory attacks.In addition to methodological advantages, importantly the system also circumvents the ethical problem posed by exposing live prey to predators which has previously hampered progress in this area. The project will develop a flexible system for studying behavioural interactions between individuals of the same or different species and will be of interest to a range of researchers working on other questions.