|
Sciuridae Sciurus niger (fox squirrel) Image Caption: Pictured is the eye of a juvenile male fox squirrel. The organ had a mass of 1 ± 0.5 g, a height of 13.6 ± 0.5 mm, a width of 14.2 ± 0.5 mm, resulting in a diameter of about half that of the 25 mm human eye (Ndabahaliye, 2002). The squirrel has a tinted coating over the eyeball which would normally hide the blue of this squirrel's eye. The covering and a tinted lens probably protect the retina from the bright sun. Assuming the shorter diameter eyeball translates into a shorter focal length and by using photographs to estimate the squirrel aperature to be less than 5 mm in bright light, compared to the human aperature of about 2.7 mm, I can estimate the ratio of light that would strike the squirrel's retina comparted to the human. The squirrel's retina would receive somewhere around 3 times more light then a human's if the squirrel had no pre-retinal absorbance. |
 Works Cited: Ndabahaliye , A. (2002). Diameter of a Human Eye. Physics Factbook. Retrieved April 23, 2009, from http://hypertextbook.com/facts/2002/AniciaNdabahaliye1.shtml. (Link)
|
|
Image Location:
United States, South Dakota,
Brookings Image Date: 2008APR18 Image Species: Sciurus niger rufiventer Sex: Male Age: Juvenile (EXIF Info is accurate – stamped in UTC). Web Page and Pictures By Peter Leitheiser Updated: 2009APR22 |