Sciuridae
 Sciurus niger
(fox squirrel)

Image Caption:
A squirrel removes the husk of a black walnut (Juglans nigra) and flings the pieces to the ground.  Next she will have to chisel through the shell.  Black walnuts are one of the hardest nuts, and the squirrels took an average of 6 minutes (n=7) to open them, although some animals were consistently faster than others.  Smith & Follmer reported an average of at least 15 minutes (1972).  To reduce seed mortality, walnut trees produce nuts hard enough to deter almost every animal except squirrels and some insects from eating them (Stapanian & Smith,  1978, p. 884), and even squirrels can't devour the crop quickly.  To further increase the chance that some nuts wil survive to seed, nut producing trees produce exceptionally large quantities of nuts in synchrony every several years, called masting (Vander Wall, 2001, p. 96).  This probably increases the chance that squirrel will cache nuts and not recover them (Vander Wall, 2001, p. 97).

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Fox Squirrel (Sciurus niger rufiventer) Eating Black Walnut (Juglans Nigra)

Works Cited:

Smith, C. S., & Follmer, D.  (1972).  Food Preferences of Squirrels.  Ecology.  54:82-91.

Stapanian, M. & Smith, C. C.  (1978).  A Model for Seed Scatterhoarding: Coevolution of Fox Squirrels and Black Walnuts.  Ecology. 59:884-896.

Vander Wall, S. B.  (2001).  The Evolutionary Ecology of Nut Dispersal.  Botanical Review.  67:74-117.

Image Location: United States, South Dakota, Brookings
Image Date: 2009SEP06
Image Species:  Sciurus niger rufiventer
(EXIF Info is accurate – stamped in UTC).

Web Page and Pictures By Peter Leitheiser
Updated: 2009SEP17