Sciurus aberti, like many other sciurids including Sciurus vulgaris and Sciurus carolinensis, shows a coat color polymorphism. Like Sciurus vulgaris, Sciurus aberti shows a correlation between coat color phase and dorsal hair length. Both squirrels show an increased frequency of dark morphs in the northern portions of their respective ranges.
Hancock, Denis C. Jr. and Nash, Donald J.
"Dorsal hair length and coat color in Abert's squirrel (Sciurus aberti),"
Great Basin Naturalist: Vol. 42
, Article 14.
Available at: http://scholarsarchive.byu.edu/gbn/vol42/iss4/14