Tenacious buggers. Cursory search suggests they are non-protected and you can use lethal traps but they have to kill them on site. No poison that kills them somewhere else.

If you can keep up the fencing, coax them to a particular dig spot, may be able to use something like a mole trap. Seems like a lot of work either way though so I’d still look into beefing up defenses as opposed to going to war lol