spirit animal vs fauna

spirit animal and fauna both are nouns.

Word	Noun	Adjective	Verb	Adverb
spirit animal	Yes	No	No	No
fauna	Yes	No	No	No

As nouns, fauna is a hypernym of spirit animal; that is, fauna is a word with a broader meaning than spirit animal:

spirit animal: An animal whose characteristics match a part of a person's behavior
fauna: a living organism characterized by voluntary movement

Other hypernyms of spirit animal include animal, animate being, beast, brute, creature.

spirit animal (noun)	fauna (noun)
An animal whose characteristics match a part of a person's behavior	a living organism characterized by voluntary movement
	all the animal life in a particular region or period