I borrowed a zwarble fo a couple of months, I didn't trust him, don't know why, but then when I had to bring them in the field shelter for a couple of days I heard the occasional 'bang' as I walked away, went back and my little black ewe would be running round, one day I bolted the door, was looking at something when 'bang' looked back quick and he's smashed straight into little ewe's side, he seemed to wait till I'd gone before laying into her, couldn't wait to get him away.
She's just had a lovely black lamb, big chunky boy.