Even in humans the state of being animals that possess consciousness varies over the course of time: new-born infants are in a different state of consciousness than 4 year old children, for example. Not to mention our regular fading in- and out and transitioning between various states of consciousness during our sleep cycle.
The first important step towards a better understanding that would allow proper assessment would be to develop a sound metric to allow qualifying consciousness. Doesn't have to be precise, but a scale from say 0 (non-conscious) to 100 (awake neuro-typical sober human adult) would be a great step forward IMHO.
Maybe we are defining consciousness differently but how do you know? how do you prove that? Don't get me wrong I too believe that animals have consciousness, but I think humans other than me have consciousness too and I can't prove that either. That's a big part of the whole issue particularly in regards to whether the current ai of the week is conscious or not.
You can demonstrate that animal and human brains achieve similar brain states given similar stimuli but how do you demonstrate that those brain states are sufficient for/require consciousness? for all we know every animal is a philosophical zombie and we can't prove otherwise.
Most animals don't have self-awareness, though some even have that, like great apes, certain cetaceans, elephants, and possibly even some birds.
The only things that seem to be uniquely human are complex language, cultural evolution and prolonged neuroplasticity during childhood and early adulthood.