Some dogs also dig when they are bored. Could you provide some interactive toys for them? A kong filled with dog food/peanut butter or some of the other treat dispensing toys. Or even a box that you cut some holes in that they have to push around to get the kibble to fall out.
You look to have highly trainable dogs, you might try to teach them to dig in only one area as someone suggested. As suggested bury toys in that area and go have a digging party there (you dig also), and without their presence quietly fill in all other holes (do not yell at the dog and point to the hole or shove their nose in it, all the dog can tell is "hey, I dig holes I get attention", unless you catch them in the act of digging, then you can yell). In unwanted holes you can try putting their feces in the hole, the vinegar water ballons, the pepper, or fill them in and put chicken wire right below the surface. Above all be consistent! Rememeber to praise them for good behavior (digging where allowed), not just correct them for bad behavior.
Happy Digging,
From the deep mining terriers.
You look to have highly trainable dogs, you might try to teach them to dig in only one area as someone suggested. As suggested bury toys in that area and go have a digging party there (you dig also), and without their presence quietly fill in all other holes (do not yell at the dog and point to the hole or shove their nose in it, all the dog can tell is "hey, I dig holes I get attention", unless you catch them in the act of digging, then you can yell). In unwanted holes you can try putting their feces in the hole, the vinegar water ballons, the pepper, or fill them in and put chicken wire right below the surface. Above all be consistent! Rememeber to praise them for good behavior (digging where allowed), not just correct them for bad behavior.
Happy Digging,
From the deep mining terriers.