I agree with Sally i would have thought it very unlikely a fox would attack a sound ewe. We have a high fox population and we lamb in December, we rarely have lambs taken, sometimes they may grab a very weak one at birth especially if mum goes down to lamb the next twin, but we pen the ewe maybe for a day or two then let mum and lamb/s out, at a couple of days old those lambs can really move so we have not lost any to foxes ( touch wood). Now ravens that's another story they come and peck lambs and ewes whilst ewe is in the throws of birthing, lost 10 lambs and 2 ewes one year to them.