2013 was hard on sheep. Rams usually survive winters a lot better than lambs and yearlings. The winter of 2013 wiped out a lot of lambs and yearlings. This last winter was rough in some reas, but not all. it will bounce back pretty quick, but we'll see the same pattern in 7-8 years from now.
Rams and ewes do get through winters differently, but it is not always hardest on the ewes. The rut puts a lot of stress on rams and they frequently fail to survive.
