Sciuridae
 Sciurus niger
(fox squirrel)

Image Caption:
A fox squirrel peers at the world with obsidian eyes.  Among mammals, the eyes of squirrels have some unique adaptations to cope with the bright light of diurnal life.  Rather than clear, the fox squirrel's lens is yellow (Walls, 1931 and personal observation) which, by absorbing a narrow bandwidth of light (mostly wavelength greater than 460 nm), may reduce chromatic abberration (Yolton, Yolton, Renz, & Jacobs, 1974).  Chromatic abberration is an optical effect that occurs because a lens refracts different wavelengths of light at different angles, causing a blurred image to form on the retina.  The trade-off is that less light enters the retina.  The nocturnal southern flying squirrel (Glaucomys volans), likely because it often copes with scarce light, has a clear lens (Yolton, Yolton, Renz, & Jacobs, 1974).

<<  Diurnal Adaptations in Squirrel Vision                           >>

Fox Squirrel (Sciurus niger rufiventer) Close Up
Works Cited:

Walls, G. L.  (1931).  The Occurrence of Colored Lenses in the Eyes of Snakes and Squirrels, and Their Probable Significance.  Copeia. 1931(3). pp. 125-127.  American Society of Ichthyologists and Herpetologists.

Yolton, R. L., Yolton, D. P., Renz, J., Jacobs, G. H.  (1974).  Preretinal Absorbance in Sciurid Eyes.  Journal of Mammalogy.  55(1) pp. 14-20.

Image Location: United States, South Dakota, Brookings
Image Date: 2009APR02
Image Species: Sciurus niger rufiventer
Sex: Male
Large Image: (EXIF information is accurate, stamped in UTC time).

Web Page and Pictures By Peter Leitheiser
Updated: 2009APR29