title: A magnetic compass aids monarch butterfly migration.
abstract: Convincing evidence that migrant monarch butterflies (Danaus plexippus) use a magnetic compass to aid their fall migration has been lacking from the spectacular navigational capabilities of this species. Here we use flight simulator studies to show that migrants indeed possess an inclination magnetic compass to help direct their flight equatorward in the fall. The use of this inclination compass is light-dependent utilizing ultraviolet-A/blue light between 380 and 420 nm. Notably, the significance of light <420 nm for inclination compass function was not considered in previous monarch studies. The antennae are important for the inclination compass because they appear to contain light-sensitive magnetosensors. For migratory monarchs, the inclination compass may serve as an important orientation mechanism when directional daylight cues are unavailable and may also augment time-compensated sun compass orientation for appropriate directionality throughout the migration.
authors: Department of Neurobiology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, Massachusetts 01605, USA.
authors: Patrick A
authors: PA
authors: Guerra
authors: Department of Biology and Biotechnology, Worcester Polytechnic Institute, Gateway Park, 60 Prescott Street, Worcester, Massachusetts 01605, USA.
authors: Robert J
authors: RJ
authors: Gegear
authors: Department of Neurobiology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, Massachusetts 01605, USA.
authors: Steven M
authors: SM
authors: Reppert
mesh_terms: D025041:Animal Migration / Q000502:physiology*; D000818:Animals; D057506:Arthropod Antennae / Q000502:physiology; D002080:Butterflies / Q000502:physiology*; D003198:Computer Simulation; D060328:Magnetic Phenomena; D012621:Seasons; D065854:Spatial Navigation / Q000502:physiology* / Q000528:radiation effects; D014466:Ultraviolet Rays; D014481:United States