No pen just tamed it by flying over dropping feet eggs near it. Had backup to protect and kill other animals. Bit so far I only have 1 and wanted it for eggs really have had better luck flying over swamp looking for their eggs on rocks and beaches.
Knock out it then place wooden spike walls around it then drop fertilized egg near the snake. When it will woke up, it will consume all the eggs and become yours. Please tap the good button to bring me happyand others can also see this tip.
You tame them by droping ferti eggs from your inv on the ground. You need to do so when the snake is not aggroed, so sit on a rex or smthing it wont attack. Be sure to drop them from your inventory, not from dino ones, that will make it bugged, it wont eat. To a lvl 20 Rex egg gives 29% on 2x event, bronto 26.7% and giga and wyvern the same, looks like all the big eggs give approxymately the same amount.. so dont waste the best you have ? If they get aggroed on you just run away and return, taming wont drop. Happy taming!