Report 17939: Possible stalking of two people walking in the early evening near Lake Michigan and Gulliver Lake (Upper Peninsula)

I was on vacation with my family at Gulliver Lake in Scoolcraft county MI in the Upper Peninsula. Me and my sister would usually take a walk after dinner. The path we would always take was Gulliver lake road ( I believe) next to the lake that looped back to our fathers cabin. Next to the lake was a wooded area that went uphill then on the other side was large sand dune. We went out later than usual so it was completly dark outside, a moonless night save a few lightpoles. As we passed the lake and made left to the other side of the wooded area where the dunes were my sister heard something but at the time she did not say anything. As we kept walking my sister would say to me that something was following us on our left side behind the treeline. We stopped to listen I thought i heard something move but was not sure. As we started to leave the wooded area behind us we both clearly heard a grunt 20 feet behind us. It sounded like a  " ooogghh" or "uuugghh". I swear it sounded as if it tellin us to get out of its territorry.