Even if something is placed on government-owned land (eg. a river), they're still bound by the fourth amendment and they can't use security cameras that surveil

Even if something is placed on government-owned land (eg. a river), they're still bound by the fourth amendment and they can't use security cameras that surveil where the owner/person has a 'reasonable expectation of privacy'. Whether or not that means the owner of the land has such expectation on hundreds of acres depends on how secure the location is; you could make the argument "anyone could legally boat down the river and see them, therefore there is not an expectation of privacy", or you could make the argument that cameras installed at an unreasonably high elevation (eg. the top of a tree on the river) would be surveilling land that nobody not trespassing could see. This is also assuming you have a legal fence/barrier that informs anyone trespassing isn't allowed, otherwise it'd be harder to claim treading the land and setting up 'wildlife cameras' is trespassing.