Social cues and habitat structure affect the behaviour of a non-social insect

Habitat fragmentation and loss is a known threat to biodiversity. Their combined effect leaves organisms in small isolated patches of habitat, contributing to the current biodiversity crisis. The first response of animals to environmental change is typically behavioural. Beyond the physical elements of the environment, the “social landscape” shapes the spatial distribution of the habitats available to organisms. In this article, we test the hypothesis that social cues and habitat structure alter behaviours in a non-social insect. We tested 86 wild-caught L. sinapis females from landscapes with various habitat structures in outdoor cages reproducing habitats with or without social cues. We demonstrate that the presence of same-sex congeners is a social signal to remain within a suitable patch of habitat. We further show that habitat structure is associated with oviposition success and investment in navigation but not with emigration. Butterflies from small, fragmented habitat patches relied more in routine movement and had lower oviposition success. Like many other insects in Europe, L. sinapis is in decline. Our results suggest that this decline may be exacerbated in degraded habitats due to behavioural strategies selected by both physical and social landscape elements.