You may be interested in a paper Thomas Negal wrote about 50 years ago called "What is it like to be a bat?"
https://www.sas.upenn.edu/~cavitch/pdf-library/Nagel_Bat.pdf
It's not just about emotional states, which we can observe the behavioral states of but don't know what it is like to experience as other animals. It's about experience and consciousness which I think speaks to the underlying question of when other animals experience an emotional state if we can relate it to our own phenomenology for similar appearing states.
Faith is belief without evidence, and I have evidence everyone who has lived so far has died and the rest of us have enough in common that would cause us to die for similar reasons as those already dead. I don't need faith to believe we're all going to die, faith would be needed to believe someone won't die because we have no convincing evidence for any immortals yet.