We once had a dog that couldn't kill a fox in a earth...she was a mixer with them but put her in a rockpile she could kill them in quick time if they couldn't bolt... she was bred out of two digging dogs to.. lives up to the age of 15 in till she drank antifreeze out of a mucky puddle from a tip while ratting...we had one pup out of the old girl who was too hard for her own good .. bitch was killed in a pile at cowling at 7 years old..