Depending on who you ask, a monkey or cat isn't conscious. From my point of view, I don't think you can really know that or recognize it. It's just a matter of degree of consciousness. I think it's safe to say that mammals are conscious to some extent. They have emotions, dreams, communication techniques, etc. we just have those (to some extent again) moreso than they do or we have them in different ways.
I think a question to ask is at what level or organization do we recognize self-direction? Am I conscious because I think so? What does that say about the bacteria that live inside of me that I rely on, or the individual neurons in my brain?
If both I and a dolphin are mostly the same, we have brains with neurons, we have blood cells, etc. how can you truly differentiate what is conscious and not? Even if you speak to another human it's not completely possible to say that they are conscious with certainty - only with what's most useful in day-to-day life.
At what level of circuity do we consider AI to be conscious? When it completes arbitrarily constructed tasks by humans? When it "feels"? How would you differentiate between sufficiently complex AI? Is there just AI or not? why?
/rambles