Mate location behaviour of the butterfly Pararge aegeria in woodland and fragmented landscapes

Visually cued mate location behaviour in insects such as butterflies is typically classified by 'wait or seek' dichotomies. Perching males adopt a sit-and-wait strategy at a particular spot rising to intercept passing females (which is often done in an aggressive territorial way), whereas patrolling males are permanently on the wing searching for females. The potential influence of changes in landscape caused by habitat fragmentation on mate location behaviour has only rarely been addressed. We investigated this behaviour among populations of the speckled wood butterfly, Pararge aegeria, living in continuous woodland versus highly fragmented agricultural landscape with hedgerows and small patches of woodland. In the latter landscape males showed higher levels of aggressive fast take-offs (an indicator of territorial perching), but also higher levels of displacement (an indicator of patrolling). In an independent census, behaviour intermediate between perching and patrolling was much more frequent in the agricultural landscape than in the woodland landscape. Our results suggest that the dichotomy of perching versus patrolling as typically observed in woodland fades away in highly fragmented agricultural landscape. We discuss our results in relation to differences in densities and thermal properties of both types of landscape.