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Monarch Butterflies
This research is conducted in collaboration with Dr. Henrik Mouritsen, University of Oldenburg, Germany. A very low friction bearing allows the butterflies to steer their intended flight directions to any point of the compass, while their headings are continuously recorded by an optical encoder and computer. This allows us to reconstruct long segments of their virtual migratory journey (Fig 2.). But what does the Monarch Butterfly use to navigate to a location they have never been to? Do they use the sun itself, the sky's polarization pattern or some combination, or do they use the earth's magnetic field? See How do Monarch Butterflies (Danaus plexippus) Navigate to Mexico? We have shown that monarchs use a time-compensated sun compass but not a magnetic compass, during migratory flight (Fig. 2). Monarchs flown under a natural sunny sky oriented southwest (Fig. 2A), those clockshifted ±6 hours, shifted their orientation 90° (Fig. 2B,C), while those tested under simulated overcast conditions were not significantly oriented suggesting that they were not using the natural magnetic field for orientation (Fig. 2D). See Mouritsen & Frost (2002).
Figure 4 shows the orientation of monarchs tested under various flight conditions. (A & B) 44° UVA-containing stimulus; (D & E) 85° UVA-containing stimulus without sunshades; (G & H) 85° UVA-containing stimulus with sun shades. None of the polarized light stimuli led to time-compensated compass orientation based on the orientation of the polarizer. When given a direct view of the sun, migratory monarchs with their polarized light detectors painted out were still able to use their time-compensated compass (Fig. 4C, dorsal-rim not occluded; Fig. 4F, dorsal rim area occluded). We conclude that in migratory monarch butterflies, polarized light cues are not necessary for a time-compensated celestial compass to work and that the azimuthal position of the sun disc and/or the associated light-intensity and spectral gradients seem to be the migrants' major compass cue. See Stalleicken et al., 2005.
SeabirdsHow do seabirds find their way? We know from previous work that migratory songbirds use at least two compasses, a magnetic compass and a celestial compass. These are known to work independently of each other. In comparison, no data are available from seabirds. The emergence of satellite transmitters have made studies of the navigational strategies of seabirds possible, since we can now follow individual birds.We have conducted navigation studies on the Waved Albatross in the Galápagos Marine Reserve in collaboration with Dr. Dave Anderson of Wake Forest University and on Sooty Shearwaters in New Zealand in collaboration with Dr. Henrik Moller of the University of Otago on the Keep the Titi Forever project.
Updated June 2005 |
Monarch butterflies (Danaus plexippus) from the eastern North
American population make remarkably long migratory journeys in the autumn,
some extending more than 3,500 km from Eastern USA and Canada to over-wintering
grounds in the neovolcanic belt in Central Mexico. 
Flight
in tethered insects is typically induced by directing a flow of air
horizontally toward their heads. We have developed a novel flight simulator
apparatus that directs the flow of air vertically from beneath the butterflies
(Fig. 1). Click 
To
test if migratory Monarch Butterflies use polarized light patterns as
part of their time-compensated sun compass, butterflies were exposed
to patches of naturally polarized blue sky, artificial polarizers or
a sunny sky. In addition, we tested butterflies with and without the
polarized light detectors of their compound eye being occluded (Fig
3).
