It's best to keep them at range with a bow or crossbow, don't try and knock them out at all. Be wary of how quick they can sneak up on you at all times near their spawn locations. Make sure you keep stimberries on your hot bar so that way you can still access them if you get bit by a Titanoboa as they will usually knock you out. Upgrading your fortitude can help counteract this so be sure to put some levels into your fortitude early on. Titanoboa's are easy to outpace but be very wary as they can climb over most obstacles so don't bother thinking your safe by hiding behind a rock or a steep slope. Killing these guys is pretty simple with any ranged damaging weapon, just run a couple of steps, turn around and fire, repeat. Make sure you keep an eye on your stamina as it can be easy to forget about it during a battle, running out of it allows the Titanoboa to catch up to you pretty quickly so manage it correctly.
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!