The ewes recognise their lambs by smell. When the lamb is licking milk, the ewes must first sniff the lamb's hindquarters to identify with their own lambs. In grazing, once they are out of the group or separated from the lambs, they echo each other with long cries. This shows that the sheep's sense of smell and hearing are more sensitive. Individual sheep have their own odor. A group of sheep have a group odor. Once two sheep are mixed, the sheep can distinguish whether they are the same group of sheep by odor.