I do feel that animal spirits can come to help you at different times and they might be of different species, maybe you'll have the same one.

There is separate concept of an animal that isn't so much as helper as your identity, perhaps a projection like an avatar, possibly deeper.

I think the term totem is used, though I believe traditionally totem denoted an animal symbol that a particular tribe shared.

Different animal spirits have come into my lives at different times, to teach or warn me about specific situations. When this happens, I might get a fascination of that species, or seem to see a flood of synchronicity involving that animal.

There is another personal concept of the animal self.

It' a hard concept to explain, it's not that I feel that I am really an animal trapped in a human body. I fully acknowledge that I'm human. Maybe I have been an animal in a past life, though my concept of time doesn't quite jibe with reincarnation, I don't believe in belief enough to discount anything entirely. Maybe it's just a deep connection of some type, but though I'm human, my astral form isn't if that makes any sense.

Some people I've met have an animal self, some don't.

I wouldn't think of it so much as summoning, but it native american traditions, they would use various ways to overcome the conscious mind to allow visions such as this to come through. Fasting, sleep depravation, repetitive drumming/dancing, hallucinogens. They would basically continue until granted a vision.

Like Drob said, animal guides come to you. Sometimes its at the least expected time. I encountered a wolf once on a vaped dmt session, and it had tried to communicate with me. However, for some reason its message could not get through to me, but I could feel that it was trying to send me a message of some sort. I guess I will never know what it wanted to show me unless it comes back and I am able to receive its message.

My dog had a third eye while I was walking around outside on a 5 gram mushroom trip. I thought of her as my spirit guide.

Though as far as spirit animals go. I have always had favorite animals, cuttlefish, stingrays, coyotes, foxes, hyenas, otters, thorny devils, chameleons, alligators, deer, bears, humans ect. but my favorite animal oddly enough is a crow, both for its symbolic significance and the fact that crows are really smart. Also the mythological storm crow, a crow that heralds storms seems pretty cool to me. Either way I say just pick an animal that resonates with you and call it your spirit animal, why not. Create your own mythology.

Unless you want to wait for an animal to come to you in a dream or a drug trip, that works too.

If I'm not mistaken, the peyote using Native Americans use a mythical blue deer as their spirit animal I think everywhere the blue deer steps a peyote button grows. I think that's the myth if I remember it correctly, though don't quote me, I'm not totally sure.