In Native American tradition, an animal guide is a person's counselor and guides and accompanies that person through life.
The creature that guides a person does not define who that person is, it simply chooses to be with them. Therefore, no one can choose their own animal guide. It would offend a guide if its identity was revealed to others. Being in touch with one's animal guide is what Carl Jung thought he invented when he came up with his active imagination technique in 1932.
Kathryn Janeway once guessed that Chakotay's animal guide was a bear, but Chakotay said that while the bear had powerful pokattah, it was not his animal guide; the only thing he was willing to reveal about his guide was that it was female.