When stealing a wyvern egg you should always have a tapajara or a pterodactyl, have your mount on passive so if you get hit by the breath attack you can get out of there fast. Try and take a level 135-150 pterodactyl or tapaja, should have enough health to withstand at least one breath attack. When fleeing the wyvern go into a group of passive creatures and do a fly by. Most of the time the wyvern will get distracted by most dinosaurs that are in groups. If that doesn't work I usually have a plan B ready. That is just having a few low level flying dinosaurs ready when I fly over them then I just whistle aggressive. That almost always works for me. Then I have a plan C, because god knows I'm always over preparing. You fly in the forest, dismount, sacrifice your dino and just run. Plan D? I'm not that smart.
There are more than one type of wyvern, they are fire, poison, lightning, and soon to be a Crystal Wyvern with the Crystal Isles free DLC coming, they are going to be a passive tame. The types of Crystal Wyverns are base, tropical, blood, and ember.
The wyverns spawn in wyvern dens, and can be found in the Highlands for Ragnarok and the Snow Desert in Valguero (I only do free DLCs).
You tame wuverns by going into the wyvern dens and finding nests with eggs in them. Once you have an egg, they need 10-15 standing torches, 4-5 fireplaces, or 20 (atleast) campfires. Until they are adults, they need Wyvern Milk to survive. That is all they eat until then.
Wyvern milk can be obtained by knocking out a female wyvern and collecting milk from there. Alpha wyverns drop more than normal wyverns.
Wyverns pick up larger dinos than other flyers.
Wyverns can breathe fire for fire wyvern, lightning for lighting wyvern, and poison balls for poison wyvern.