First off, you can use a regular bola on them. It will immobilize them like normal, however you still cannot feed them. You can only feed them when they are Chain Bola'd.

Second, the easiest and fastest method we have found is to trap them and then shoot them until their health is low, which will cause their food to rapidly decrease in order to heal the damage. Let their food get down past half, maybe even 25% and you can feed them once every 5 secs or so to tame them super quick. Good luck out there.

More Tropeognathus Taming & KO Tips