to echo @teellbee, we don’t really know, but we can try to interpret animals’ reactions. some studies do let us see electrochmical responses in the brain, etc., but that’s not the same as understanding what it feels like, ie., empathy.
I’d advise that people use caution when trying to interpret animals’ signals. Many species are fantastic communicators and will clearly display their emotions, mood, and intents… but we are not usually the “intended” audience and we can easily mis-interpret signals or miss them entirely.
Although, there is little to mis-interpret in the snarl of a wolf, or the loafing of a pet cat.
