Theory:

He wore a question mark for tail,
An overcoat of gray,
He sat up straight to eat a nut.
He liked to tease and play,
And if we ran around his tree,
He went the other way.
 
                    — Mildred Bowers Armstrong
Reference:
National Council of Educational Research and Training (2007). The Squirrel - Mildred Bowers Armstrong (pp. 17). Published at the Publication Division by the Secretary, National Council of Educational Research and Training, Sri Aurobindo Marg, New Delhi.