The measurements showed that fresh degu urine reflects UV much stronger than the longer wavelengths of the spectrum. In contrast, dry old urine mostly reflects longer wavelengths and very little UV. With their UV-sensitive eyes, degus have the potential to discriminate fresh urine marks from old ones not only by olfaction, but also by vision. Degus can see where a conspecific has recently walked by, and where the current social "hot spots" are. Olfactory signals are dispersed by air movements and are, hence, rather imprecise markers of location. The visual detection of urine marks should significantly improve localization. This may have been the evolutionary pressure to maintain UV vision.
The hypothesis can be extended to other rodent species. Some species are also known to produce UV-reflecting urine and use it for scent marking (e. g. mice and rats). Previous studies in these species have not addressed the potential link between UV vision and urine UV-reflectance. There is also, however, a drawback associated with the potential advantage of visible scent marks. Diurnal
'"/>
Contact: Dr. Leo Peichl, Max Planck Institute for Brain Research
49- 69-96769-219
Max-Planck-Gesellschaft
10-Jun-2003