Hi Kerry
If one hog was circling the other and the one being circled was turning around inside the circle, making a rhythmical huffing sound, it was a male circling a female. (although you said no sound, which is strange). It’s still quite early, but if there are males and females around, is likely to happen. It’s part of their, kind of, courtship. The circling can, at times, go on for hours.
It isn’t always easy to say just from a short description. It could just have been one hog checking out another for some reason.
