Supplementary material from "Narrow anthropogenic corridors direct the movement of a generalist boreal butterfly"

Ecological and anthropogenic corridors are becoming more common worldwide, but little is known about how corridor size (width) affects species' movements, and thus their effects. Here we investigated whether 4- and 8-m wide anthropogenic corridors (seismic lines) cleared for petroleum (oil sands) exploration in boreal forests in Alberta, Canada, act on altering the behaviour of a habitat generalist butterfly, the Arctic fritillary (Boloria chariclea). Specifically, we captured 539 Arctic fritillaries and released them in seismic line corridor or control sites with no structural directionality (i.e. forests and clearings), and recorded both their initial direction (along the seismic line or not) and persistence in directional movements. Arctic fritillaries moved inside these lines twice as often as they left them, and maintained their initial direction more often, regardless of line size and independently of forest structure or sex of individuals. Thus, anthropogenic corridors as narrow as 4 m can affect insect movements. Given the vast area of boreal forests disturbed from seismic assessments, investigating if the effects of these dense, localized lines affect population dynamics and species interactions would provide important insights to managing this ecosystem and identifying restoration actions.