Sorry, I meant "tethered" weather balloons. Which I assume would solve the "recover-ability" issue. No idea on "stability".
However, if you just want to get rid of the pigs, not kill them, I could imagine that you could do pretty well herding them with a loud RC helicopter... perhaps even herd them into a trap or kill-zone.
So if you could get them high enough for the noise not to be a big issue, and to give them a reasonable coverage with the camera, you can easily put a few of these up in a network on autpilot (with way points) and just watch several screens at once.
It also appears, from the guy's videos, that he has a large area of ground to cover, and with the limited optics and image resolutions he's working with, a tethered balloon wouldn't be very functional.
He should just stick with his plane idea.