Today at the state park, Isaac raced ahead of me into the woods as usual, then about the time I reached the woods, he came running back out. I thought that was odd and didn't understand why.
A minute later I heard voices and realized there must be other hikers on the trail, even though I hadn't seen any other cars in the parking lot. Isaac heard people too, and started to run back into the woods to greet them. Because of course he think everyone wants to meet him and be his friend.
I started to follow him and then got my first glimpse of the people. They were not hiking, they were on horseback!
Isaac has had limited experience around horses and that must have been why he came running back out of the woods the first time.
The second time, he stood on the trail, staring at them intently, tail wagging like he thought he wanted to make friends but wasn't quite sure. Then he barked a couple times. I put him back on leash and moved him out of the way, and also told him to quit barking which he did, so the riders could pass.
Luckily their horses were not at all concerned about my silly dog. Isaac watched them for a quite a while before he was ready to hike, though.