Fs it's a 4 month old terrier pup common sense lads it's only of the tit it's a baby but it's not like you'll be using it for a digging dog but at that age fs it wouldn't know what's happening so no need to hold it back let it grow up be a pup and when ever you see it switch on a bit start giving him a couple of rats out of trap before you know it he'll be on the job on his own