Is there something special about where they're digging for it to be plagued with such a large amount of rats? It looks like it would take weeks to cover all of their land with this digging + dog method.
That building you can see at about 30 seconds in is on skids, it is a barn/coop for chickens (or perhaps some other similarly small and light animal).
The bottom of the building is slatted to allow waste and other debris to fall through.
Because it's warm, and there's a constant sufficient supply of food it's an attractive home for rats and mice.
On some kind of regular schedule, the barn will be pulled along to a new location to allow the droppings/waste to be cleaned up, and the rats to be killed off.