The dossier says:
"Found only in the dark caves of the island"
They are already wrong! It should say something more like:
"Found everywhere but the dark caves of the island, this creature will gladly ruin your day by jumping out and killing you as soon as you even think about going to the swamp. Nearly impossible to tame because it has to be tamed via passive which is very difficult to do. Worst of all you need to feed them fertilized eggs. Why can't it e a little easier?
If you kill it and look in its inventory, its got a lot of good stuff like bows, armor, and arrows or cooking recipes. I use bows and pikes to kill them, and pack stimberries. Im playing on easy-casual on ark mobile so might not be the same for other versions.