How dim is dim? Precision of the celestial compass in moonlight and sunlight.
Author
Summary, in English
Prominent in the sky, but not visible to humans, is a pattern of polarized skylight formed around both the Sun and the Moon. Dung beetles are, at present, the only animal group known to use the much dimmer polarization pattern formed around the Moon as a compass cue for maintaining travel direction. However, the Moon is not visible every night and the intensity of the celestial polarization pattern gradually declines as the Moon wanes. Therefore, for nocturnal orientation on all moonlit nights, the absolute sensitivity of the dung beetle's polarization detector may limit the precision of this behaviour. To test this, we studied the straight-line foraging behaviour of the nocturnal ball-rolling dung beetle Scarabaeus satyrus to establish when the Moon is too dim-and the polarization pattern too weak-to provide a reliable cue for orientation. Our results show that celestial orientation is as accurate during crescent Moon as it is during full Moon. Moreover, this orientation accuracy is equal to that measured for diurnal species that orient under the 100 million times brighter polarization pattern formed around the Sun. This indicates that, in nocturnal species, the sensitivity of the optical polarization compass can be greatly increased without any loss of precision.
Department/s
Publishing year
2011
Language
English
Pages
697-702
Publication/Series
Philosophical Transactions of the Royal Society B: Biological Sciences
Volume
366
Issue
1565
Document type
Journal article
Publisher
Royal Society Publishing
Topic
- Zoology
Keywords
- orientation
- polarized light
- dung beetle
- vision
- navigation
Status
Published
Research group
- Lund Vision Group
ISBN/ISSN/Other
- ISSN: 1471-2970