They need to do that, but they’re thinking like city people and civilized human beings who don’t grasp the rape, pillage and plunder relationship with nature that drives these idiots.
If they don’t throw up a perimeter, these idiots will poach every last deer, raccoon, possum, squirrel, songbird, or any other critter that isn’t hibernating they can reach on foot. It is an ideological, hormonal and psychological imperative for them that they do just that. They’re looking forward to it. On the upside, eating the wildlife somewhat increases the chance they’ll end up with some kind of gastrointestinal illness or one of the many diseases that are endemic among small animals in the wild, resulting in a quicker surrender, but it’s really not worth letting them kill all the animals on the chance they’ll make themselves sick.
Also, without a perimeter–and miserable work manning it will be–their fellow idiots will backpack food into them.
They could probably keep the idiots from desertifying the immediate area and prevent smuggling with drone coverage and a quick reaction force rather than a perimeter, but that would up the odds of conflict resulting in dead people, which is the opposite of what they want.