Visual social cues and habitat structure influence the behaviour of a nonsocial insect

Habitat fragmentation and loss is a known threat to biodiversity. Their combined effect leaves organisms in small isolated habitat patches, 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. Here, we test the hypothesis that visual social cues and habitat structure alter behaviours in a nonsocial insect, the wood white butterfly (Leptidea sinapis, Linnaeus 1758). We tested 85 wild-caught female individuals from landscapes with various habitat structures in outdoor cages reproducing habitats with or without visual 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 smaller, more fragmented habitat patches relied more on routine movement and had lower oviposition success compared with those from larger, less fragmented patches (except at the highest temperatures). Many insect species in Europe, including L. sinapis, are reportedly in decline. Our results indicate the importance of considering both physical and social landscape elements when assessing the impacts of landscape changes on insect behaviour, and consequently in the planning of conservation and habitat restoration efforts. Applying this approach to other nonsocial insects will be critical to fully understand how habitat structure influences their populations and contributes to declines.