Sciuridae
Sciurus niger
(fox squirrel)

Image Caption:
When examining me, fox squirrels will sometimes bob their head up and down a few centimeters several times.  Although I do not know what this behavior is for, I suspect it is to increase visual parallax so they can more accurately access the distance from me to them.  I must, however point out that I’ve only seem them do this when they were less than five meters from me, and the closer one is to something, the easier it is to judge distance and the less necessary greater parallax would be.  Another hypothesis is that they watch my eyes to see if I follow their motion, to see if I’m alive.  The animal would have to be dangerously close to a predator, though, for this to work.

Similar behavior is observed in the northern flying squirrel before launch.  This animal will sway its head from side to side (Vernes, 2001), probably to more accurately judge the distance of the next jump.

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Fox Squirrel (Sciurus niger rufiventer) in Two Positions

Works Cited:

Vernes, K.  (2001).  Gliding Performance of the Northern Flying Squirrel (Glaucomys sabrinus) in Mature Mixed Forest of Eastern Canada.  Journal of Mammalogy, Vol. 82, No. 4 (Nov., 2001), pp. 1026-1033.
Image Location: United States, South Dakota, Brookings
Image Date: 2008DEC06
Image Species: Sciurus niger rufiventer
 (EXIF Information is accurate – stamped in UTC).

Web Page and Pictures By Peter Leitheiser
Updated: 2009JAN01