Behavioural variation in background colour matching and the effect of social environment in rock-pool mosquitoes

Several animal species conceal themselves from potential predators by actively choosing environmental patches that best match body colouration and chromatic patterns. Growing evidence shows that a variety of contexts and conditions can affect this background choice behaviour, yet the extent of this variety remains largely underexplored. Here, we explore the effect of disturbance and social environment on background colour choice behaviour in the rock-pool mosquito Aedes mariae. We exposed single individuals and groups of individuals to experimental arenas made of dark and bright patches, and recorded individuals colour preferences when alone and within groups, as well as before and after a disruptive event. We found a marked prevalence of individuals favouring a dark background and an among-individual variation in choice over replicated trials. Moreover, we observed a non-significant effect of disturbance but a significant role of the social environment. In fact, being caged in groups significantly increased the proportion of mosquitoes choosing the dark background. Our results provide strong evidence of a background colour choice in Ae. mariae, a density-dependence of this choice, and a non-negligible inter-individual variation in this behaviour. Overall, these findings offer intriguing insights into the background choice behavioural variation and flexibility in mosquitoes.