Why did the butterfly cross the road? Ecological effects of roadside mowing on butterflies (Lepidoptera: Hesperioidea and Papilionoidea)

Studies on road ecology and vehicular collisions with animals have primarily focused on vertebrates, leaving invertebrate taxa rather underrepresented. The vegetation in roadside right-of-ways (ROWs) in North Central Florida is routinely mowed to maintain both highway safety and aesthetics, yet ROWs have the potential to provide habitat for many invertebrate taxa. The objective of this study was to investigate alternative ROW mowing treatments and their effects on butterflies (Lepidoptera: Hesperioidea and Papilionoidea), which may be using the ROWs as habitat. Three different mowing treatments were applied to sections of ROW along highways in Alachua County, Florida: no mowing, mowing every 6 wks, and mowing every 3 wks. Each treatment was applied along a 200-m-section and was replicated eight times. Living butterflies were counted using linear transects and dead butterflies were collected from the roadside. Relative mortality was calculated and compared between the three treatments. Differences between living butterfly counts, dead butterfly counts, or relative mortalities may suggest differences in habitat suitability and mortality risk. Floral species richness and density per square m were also compared between the three treatments. Correlations of the floral variables to the butterfly variables were also investigated. The study covered one flight season from mid-April through late-October. Butterflies were chosen because they serve as practical ecological indicators for other flying insect pollinators. The long term goal is to address the Florida Department of Transportation with a mowing treatment that would accommodate both highway safety and pollinator conservation.