If you stumble upon a pack of sabertooths, make sure you have a movement speed of atleast 120%. If you do, run like heck away if you don't have any ranged weapons. If you have a range weapon and have atleast 130% speed, run on top of a rock and shoot the sabre. They die very quickly from any weapon since they have a weak health build.
You find these just about everywhere. Mostly in the tundra in small 2-3 packs. However, you may also find packs of them in the redwood mountains or large grass plains, and of course on carnivore island.
For those who read my rex story (about a rex on the other island and swam back a couple of seconds later and I was killed by a scorpion) This devil killed me the second when I reopened (near forest) I thought they were only in tundra or snow, I guess not :(