When raising a Wyvern make sure it's food does not plummet to low. Lower level babies may not have 1200 food so you may need to force feed the milk rather then having it feed itself. Imprinting with milk also counts as a feeding, so don't feed him milk before an imprint!
I got a level 150 lightning egg and I was so excited to hatch the egg...that when I went to put the egg down I accidentally ate it instead. :( ps4 users: R2 ISN'T GONNA DROP THE EGG YOU'RE GONNA EAT IT LIKE ANY OTHER EGG. REMEMBER THIS. LOGIC BEFORE EXCITMENT.