Movement across woodland edges suggests plantations and farmland are barriers to dispersal

Context The behavioural response of animals to edges between habitat patches and the matrix can influence population dynamics and species persistence in fragmented landscapes. Objectives We aimed to answer two questions: (1) How do edge-effects between three land-cover types affect movement of adult male butterflies, and; (2) is response to edges influenced by perceptual range? Methods In south-eastern Australia, we visually tracked the flight behaviour of the butterfly Heteronympha merope at edges between three land-cover types: native eucalypt woodland, farmland and exotic pine plantation. Using six replicates of each edge type, we released animals on both sides of the edges, and at two distances from the edge (5 m and 30 m). Results Butterflies avoided pine edges, appeared to have low perceptual range in pines, and when released in pines, departed quickly. Butterflies often crossed from farmland into woodland and stayed, whereas none crossed from woodland into farmland or pines and stayed. Butterflies moved further away from pine edges when they were in woodland than when they were in farmland, suggesting edge-effects of one land-cover type depend on how animals respond to the alternative land-cover. Conclusions Avoidance, and low perceptual range in plantations suggests plantations reduce landscape connectivity. Limited use of farmland is consistent with global reports that intensification of agriculture contributes to insect declines. Resource requirements of butterflies overlap with many other insects, and so extensive forestry plantations and intensive agriculture likely have negative impacts on a range of taxa, with improved land-sharing a possible solution.

Automated summary

The study found that butterflies exhibit avoidance behavior at the edges of plantations, with low perceptual range in these areas, leading them to quickly depart. Butterflies often cross from farmland into woodland and stay, but hardly any cross from woodland or plantations into farmland and stay. The distance butterflies move away from plantation edges in woodland is greater than in farmland, indicating that the edge-effects of one land-cover type depend on the animals' response to the alternative land-cover.