Evaluating the Use of Highway Corridors by Monarch Butterflies

In response to the decline of critical pollinators, including butterflies, a presidential memorandum entitled, “Creating a Federal Strategy to Promote the Health of Honey Bees and other Pollinators,” established the Pollinator Health Task Force. The U.S. Department of Transportation is a member of this task force and is tasked with evaluating its current guidance and identifying opportunities for establishing pollinator habitat and promoting pollinator friendly practices in transportation corridors. The monarch butterfly is found throughout the lower 48 states, Hawaii, southern Canada, and northern South America. Because of its large bright orange and black-patterned wings and its migration path spanning much of the northwestern hemisphere, its decline has been more noticeable than most other pollinators. This butterfly has experienced a 59 percent decline, based on observations when they are concentrated in overwintering grounds. Reasons for its decline: habitat and food source loss; invasive plant species that outcompete milkweed; species both native and introduced that mimic milkweed and fool the butterfly into laying eggs where the milkweed required for the larval stage does not exist; pesticide use; and illegal logging in its very limited overwintering grounds. Milkweeds, which provide food for the larval stage, are often considered “weeds” in need of eradication in agricultural settings. Research is needed to expand on the existing body of knowledge around roadside pollinator habitat to provide a better understanding of the relationship between long-term maintenance and roadside management activities. In particular, the information will assist in evaluating potential tradeoffs between providing monarch butterfly habitat and safety concerns relative to changes in maintenance practices to maintain the habitat. The objectives of the research are to (1) provide objective answers as to whether planting native species, including the milkweeds preferred by the larval stage of the butterfly and nectar producing plants for the adult stage, along roadways contributes to sustainable or increased populations; (2) produce implementation guidelines on the minimal area of plantings needed to create effective habitat enhancement for the monarch butterfly, as well as location of plantings in the roadside topography, and whether planting too close to the roadway may increase butterfly mortality through strikes by vehicles or mowing plants when larvae are present in clear zones; and (3) provide information to state departments of transportation about the impacts of transportation on and benefits and drawbacks of planting milkweed and nectar providing plantings for the butterfly.


  • English


  • Status: Proposed
  • Contract Numbers:


  • Sponsor Organizations:

    National Cooperative Highway Research Program

    Transportation Research Board
    500 Fifth Street, NW
    Washington, DC  United States  20001

    American Association of State Highway and Transportation Officials (AASHTO)

    444 North Capitol Street, NW
    Washington, DC  United States  20001

    Federal Highway Administration

    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590
  • Project Managers:

    Rogers, William

  • Start Date: 20160512
  • Expected Completion Date: 0
  • Actual Completion Date: 0
  • Source Data: RiP Project 40856

Subject/Index Terms

Filing Info

  • Accession Number: 01599005
  • Record Type: Research project
  • Source Agency: Transportation Research Board
  • Contract Numbers: 20-119
  • Files: TRB, RiP
  • Created Date: May 12 2016 1:00AM