deer mouse

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A North American mouse (Peromyscus maniculatus) having white feet and underparts, and a long, bicolored tail.

from The Century Dictionary.

• noun A common name of the American jumping-mouse, Zapus hudsonius, the only member of the family Zapodidæ (which see): so called from its agility.
• noun A popular name of several species of true mice indigenous to North America, of the family Muridœ and genus Hesperomys.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun brownish New World mouse; most widely distributed member of the genus