Two squirrels frolic on a sidewalk in Alexandria, Va. Monday, June 5, 2006. (AP Photo/Gerald Herbert)

A squirrel allows his legs to dangle freely as it lounges on a section of fence in Alexandria, Va. Sunday, Aug. 1, 2004. (AP Photo/Gerald Herbert)

The Richardson ground squirrel uses ultrasonic frequencies to provide a warning to fellow members of its group, the first time an animal has been found to use high-frequency sound this way.(AFP/File/Paul Richards)

A moose named Zero stands in a wildlife park in Gray, Maine, on Wednesday, May 5, 2004. A moose's bulbous nose adds to the cartoonish look of the gangly creature. Two researchers decided to take a closer look at the unconventional snout. Among their findi