Stress shouldn't be considered a human emotion, or an emotion at all if you ask me. All animals can experience stress. There is distress and eustress.
Merriam- Webster's Dictionary
Distressed is another way of saying upset, disturbed, afflicted, pretty much something the animal doesn't like to experience, whether that be physically or as in a situation.Pain or suffering affecting the body, a bodily part, or the mind : trouble, a painful situation : misfortune: a state of danger or desperate need
But that's just my two cents.