Behavioural modes in butterflies: their implications for movement and searching behaviour

Animals move in ‘modes’ where movement patterns relate to specific behaviours. Despite much work on the movement of butterflies, their behavioural modes are relatively unexplored. Here we analysed the behaviour of the model butterfly species the meadow brown, Maniola jurtina. We identified modes in both sexes and across habitats varying in resource density. We found that, in nectar-rich habitats, males had more diverse behaviour than females, engaging in a unique ‘high-flight’ mode associated with mate search, whereas females were primarily nectaring or inactive. In nectar-poor habitats, both sexes were similar, switching between flight and inactivity. We also identified the movement parameters of the modes, finding that, for both sexes, movements associated with nectaring were slower and more tortuous and, for males, the mode associated with mate searching was straighter and faster. Using an individual-based random-walk model, we investigated the effects of behaviour on movement predictions by comparing a mode-switching model with a version including intraspecific variation and another assuming homogeneity between individuals. For both sexes, including modes affected the mean and shape of the displacement rate compared to models assuming homogeneity, although for females modes increased displacement 1.5 times while for males they decreased it by a third. Both models also differed substantially from models assuming intraspecific variation. Finally, using a new model of search behaviour we investigated the general conditions under which individuals should engage in an exclusive search for host plants or receptive females. Parameterized for M. jurtina, the model predicted males should engage exclusively in mate search, but females only when searching is very efficient. The model provides a framework for analysing the searching behaviour of other butterfly species.