SFB-TRR 212

Behavioural niche choice: personality differences and unpredictability in escape behaviour

Throughout life, animals are faced with a number of challenges and individuals differ from each other in how they respond to them. This results in alternative individual behavioural strategies that can coexist in a population. Escape from predators is a behavioural context in which behavioural strategies are particularly manifold. A poorly-explored component of such strategies is behavioural (un)predictability in the timing and execution of flight behaviour in prey species. The predictability-unpredictability axis represents a dimension of animal personality that, due to methodological constraints, has only recently gained some of the attention that it deserves. Escape behaviour is particularly interesting in this context, because it offers scope for trade-offs of behavioural predictability with maximized efficiency in escape distance.

In the extreme, strategies can be classified as maximally unpredictable ('the hare strategy') or as predictable, but efficient in the use of a straight, long-distance escape path ('the gazelle strategy'). The hare strategy seems particularly advantageous in rich, complex habitats where unpredictable individuals can hope to find cover for hiding, while the gazelle strategy is more efficient in unstructured habitats. Similarly, unpredictability in behaviour will be more efficient when individuals are well camouflaged. Moreover, the relative fitness of escape behaviour may critically depend on the costs associated with escape movements in terms of energy requirements and risk of injury and mortality, with higher costs favouring a more unpredictable strategy.

I propose to study the behavioural ecology of intra- and inter-individual variation in behavioural variability in the context of escape behaviour in grasshoppers. The project aims to quantify the relative role of environmental and genetic influences on such behavioural variability using quantitative genetic tools. Furthermore, I propose to manipulate environmental complexity to study

1. adaptive phenotypic responses to environmental variability and
2. individual strategy-dependent preferences for habitats of different complexity.

By following individuals throughout life, I will also be able to study the ontogeny of (un)predictability in behaviour across multiple life stages. Using multiple field populations that persist under different predation risks, I aim to test for local adaptation in replicated natural populations with and without high abundance of web-building spiders that increase the risk associated with escape moves and thus likely favour increased unpredictability. Moreover, I will test for condition-dependence in (un)predictability to assess whether unpredictability is better interpreted as a virtue or as an imperfection in performance. Finally, I will test for the fitness consequences of variation in predictability using human subjects as visual predators in a computer simulation.