If someone else started the process prior to you, actually seeing the Old Sabertooth die (see the death notification text) enables you to get the key item without first examining the bones to spawn the Sabertooth.
Note: If you do this quest with several of your characters, make sure you aren't holding the Ranger's Necklace from another character, as this will prevent you from completing the quest. If you do, you will get a message that you should return after sorting your inventory (normally refers to a full inventory).
In order to become a truly great hunter, one must be accepted by Mother Nature. In order for that to happen, one must gain the fang of a tiger, the fanged king. But it does not sound like any old fang will do...
SPOILER WARNING: Click here for additional details about this story line.