If you wish to kill it by hand, make sure you have some type of long range melee weapon. As long as you are playing on a non modded version of Ark, pikes work best. Keep out of it's bite range (for if it hits you without proper armor you'll be knocked out and eaten), and hold down the attack button.
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? Up-vote of you agree!