I have horses, dogs, and a cat. The only one who seems to have noticed so far was my male horse (and he knew before the tests told me!)
Male horses are able to sense when a woman is on her period, or close to it. And he will often act a little more needy for attention when my AF is due. However, this month, a week before I got my BFP he started being EXTREMELY needy. As in LICKING my jeans, my arms, any part of my clothing that he could get to. And nudging my legs and hips with his nose. He DEFINITELY knew!