Let’s hope this person has an exploratory conversation with the neighbor first! They’ll need to ask a bunch of questions about why the neighbor is choosing to use this camera. They should let the neighbor do most of the talking, and then state their case.
Although this person is used to the tranquility of their family’s property, this new neighbor might not be. As they settle in, they might be making adjustments (hence the signs, for reasons that people elaborated on down below). I think it’s totally plausible that the neighbor picked a tree, glanced around, and thought, “Yeah sure, that’s a fine spot for the trail camera.” They might not be totally wedded to the idea of having the trail camera in that particular spot forever.
As some people pointed out, this person could be after deer or other local wildlife, and wants to track their habits or migratory paths. They might be security minded, and think that that’s the best choice for their property. And, as some folks noted, the trail camera can’t actually see that far into the distance, so it might not really be that big of a problem. But I still understand why you wouldn’t want to be on camera at your house in the middle of the wilderness. Even if the camera can’t see them, a lot of people just do not want any tech in their woods, feeling that it defeats the purpose of being in the great outdors.


