If your going to keep the discussion on whether or not they "can sense physiological changes in an animal or person they are near or touching"
Then yes, I totally agree. I just dont know the threshold that they can sense to. If we give off hormones or some scent of "fear" then they will probably be able to smell it with how sensitive they are.
Do I believe they recognize it as fear? No, I think they view it as high stress, discomfort, or a restless scent.

I think they pick up vibrations extremely well. Can they feel our heartbeat when they constrict? Heck yea they can. Have you ever had your Blood pressure taken? I can feel my pulse through my ears at that point.
They may be able to associate that with an animal being alive and not ready for eating, or not. I don't know.

Do I believe in biorhythms? Not in the sense that they can know or identify our moods. That again would lead to them reasoning and having the ability to understand moods or thoughts.
But for physiological reasons, they probably can tell what's going on concerning stress and eustress.