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.
These guys are super scary. no matter how powerful you are, always watch out for these guys if you're in or around a swamp. swamps are FILLED with these guys, and when they bite you, they fill your torpor bar up and knock out both you and your mount. DO NOT get knocked out, especially when in a dangerous area like a swamp. if you get bitten, eat a bunch of stimberries and feed them to your mount too. my pteranodon and tapejara and me can take out almost anything we come across (so far), and i'm still terrified of these guys. stay away from titanoboas and other poisonous creatures, even if they're not powerful they'll get you killed. keep at least 50, preferably 100-200 stimberries on you when traveling through, over or near swamps.
To collect eggs, build a 2 room pen (Dino gates work great as walls and dividers). Agro a bunch of TBs and lead them to one side of the pen then trap them in. Lead them back and forth between the sides as they drop eggs.