You can also put a non routing scripted commander in the top left or bottom left corner or your position screen and have him hold/cast spells (if it's not a priest(ess) and if/when the mammoths/elephants rout they won't run him over since they run in a straight line.

Also what Alex said . High numbers of hard to kill units will make the unit have a greater moral. Then of course Sermon of Courage/Fanatism... Also nature Users have a spell called "Berserkers" which works like a charm for Elephant/Mammoth patrols.

Not to step on your toes Alex