Bring lots of shock tranq darts and long neck rifle... maybe 2 or 3 shots to take down a wyvern, but they are back up very fast (less than 45 seconds). Get the first egg you see and then run. AFTER it hatches, go back to get the milk. If you get the milk before it hatches, it will spoil because it can't be refrigerated. Female wyvern give you 5 milk... this should be all you need.