Roadside Environments and the Effects of Roadside Management Practices on Milkweeds and Monarchs

Abstract

The potential of roadsides as habitat for wildlife has gained interest in recent years, with research suggesting positive effects for several taxa. Roadsides cover a vast area in the United States, and are actively managed by state and federal agencies. However, not much is known about the potential of roadsides to provide habitat for the monarch butterfly (Danaus plexippus). Therefore, I assessed milkweed densities on roadsides and in adjacent lands, the effects of different mowing times in roadsides on milkweed density, number of stems per plant, plant height (cm), and latex production, and mortality rates for monarch butterflies on roadsides oriented in a north/south and east/west direction during fall migration. My results show Asclepias viridis and A. asperula milkweed densities are higher on roadsides than adjacent lands in Oklahoma; mowing roadsides lowers counts of A. viridis milkweed but those lower counts are limited to the actual times of mowing; monarch mortality during fall migration did not differ with highway orientation. Although additional research is needed, roadsides have the potential to provide monarch butterfly habitat and should be considered when assessing conservation strategies.