Can there only be human ghosts?

In theory there can only be human ghosts, but this is because a ghost is usually defined as a human lindering spirit. But then we get into other sections where people might see something like an old horse buggy go by that dissapears. This is not really a ghost as much as like a time stamp in a moment from the past. I have never encountered anything like this but in books, they mostly say this is what can be accounted for if you do witness a scene in time rather than a ghost who looks directly at you or a ghost that u might see in different areas in the house. The reason I say in different areas of the house is beccause if you see a person like a ghost in the house but the sillouette or person always does the same thing, this may also be like a time stamp from a dramatic past. There are also demons which are different and usually can be associated with great fear when you witness anything like this. If you see a large man come down the hallway but notice his face is more like a bull than human and he slightly makes you want to change your pants, then this would be more associated with a demon than a ghost. Ghost usually are in a area already and cannot easily move to a different location. Rather I don't believe they have that ability. Demons however are brought to a place possible by past experiences such as people using a quija board or summoning spirits. Demons also can imitate more of a ghost like form but have the ability to follow or strongly change moods or actions. Soo are their only human ghosts? yes..