It seems like there are a half dozen or so miscellaneous quests that require a mammoth tusk, and I personally hate killing anything that isn't hostile towards me (killing mammoths reminds me of those people shooting bison for fun from a train in mid 1800's america). And why should I when there are hundreds of mammoth skulls lying about?
This mod makes it possible to harvest mammoth tusks from any mammoth skull (check out the mammoth burial grounds northwest of Loreius Farm, and the jarls longhouse in Winterhold). Now you can fulfill all those quests without slaughtering a single mammoth.
Should be compatible with everything that doesn't alter the mammoth skull statics.