well, actually, in relation to animistic spirituality practiced by natives, they are properly called totems, and calling them "spirit animals" would be highly insulting to the totem
the whole "spirit animal" thing is really a hippie white person thing that came about when the LSD crowd started combining LSD use with certain elements of animistic spirituality
either way it is annoying and people who use the term "spirit animal" (such as "going on long jogs in the morning is my spirit animal") come off as being clueless in almost all cases