Kenneth G. Wilson (1923–). The Columbia Guide to Standard American English. 1993.
buffalo, bison (nn.)
As every schoolchild should know, the American bison is not a buffalo at all. Buffaloes (or buffalos or buffalo; see PLURALS OF NOUNS ENDING IN -O) can be any of several wild oxen that live in Africa and elsewhere, but not in North America. Nonetheless, buffalo persists as the popular name for the American bison, especially in the Wild West of history and imagination, and both words are Standard English, except in biologically precise use, where bison must prevail.
