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Journal of Experimental Biology, Vol 202, Issue 9 1159-1166, Copyright © 1999 by Company of Biologists

JOURNAL ARTICLES

Evidence for orientation using the e-vector direction of polarised light in the sleepy lizard tiliqua rugosa

MJ Freake
School of Biological Sciences, The Flinders University of South Australia, GPO Box 2100, Adelaide, SA 5001, Australia. mfreake@bio. indiana.edu.

Adult sleepy lizards (Tiliqua rugosa) were trained to orient in a predictable direction under natural sky light in outdoor pens. When tested under clear skies in the late afternoon, without a view of the sun, the lizards exhibited a symmetrical bimodal pattern of orientation with respect to the trained axis. Since the e-vector of polarised light provides an axial rather than a polar cue, the bimodal orientation exhibited by the lizards is consistent with the use of a celestial compass based on sky polarisation patterns. To confirm that the lizards could orient with respect to a polarisation pattern, lizards were trained in indoor pens to orient in a predictable direction under a linearly polarised light source. When tested in a circular arena illuminated by another polarised light source, the lizards used the e-vector direction of the polarised light source to orient along the trained axis. There was no evidence that the lizards were using any room-specific cues or brightness patterns to orient in the training direction. These results support the hypothesis that the lizards can use the e-vector direction of polarised light in the form of a sky polarisation compass.




© The Company of Biologists Ltd 1999