Since wyverns are passive tame ride one and out dini gates in one of your selective boxes. You don't have to agro the managarm. Just try to put down the dini gates normal size right behind the wings and neck and another in front of legs but over neck. Box it in with dino gates as quickly as possible. You don't have to get off the wyvern. But I guess you could do it with any flying dino. Be careful not to get frozen.