Landscape factors influencing roost site selection by monarch butterflies Danaus plexippus during fall migration in Ontario, Canada

Abstract

Worldwide, insect populations are declining, and the eastern migratory group of the monarch butterfly Danaus plexippus in North America has not escaped this fate. The conservation of this iconic species is an international priority but requires knowledge of how monarchs interact with the landscape during different stages of the annual cycle. To better understand habitat needs of monarchs departing their core breeding range in southern Ontario, Canada, we examined how various landscape features influenced roost site selection during fall migration—an instrumental resource link between the breeding and wintering grounds. Using dedicated fall migration surveys along the Great Lakes coastlines and a citizen science dataset collected across all of Ontario, we evaluated the relationship between roost site occupancy and 18 landscape variables using a boosted regression tree (BRT) modelling approach. Results suggest that a closer distance to the Great Lakes, increased goldenrod Solidago spp. cover, moderate forest cover, rural road cover, and urban land cover are all important to roosting site selection. Our research provides important insights into the habitat characteristics of stopover sites, which will help guide future investigations and conservation actions to preserve monarch butterflies and their migratory phenomenon.