Definitely! I was away earlier this year, and my housemate was minding the cats, and there was some ghostly activity going on (so much so even we knew about it). The cats were just going nutz, running around and meowing strangely. I have seen it before myself.

I like the concept of "veils" being thin in humans, and I also think that animals are naturally attuned to what goes on in the next life. My two remaining kitties, Pixie and Randie, certainly behaved oddly when Nibbler passed on to the Bridge.