For some wyverns you don’t necessarily NEED wyvern milk to imprint them or get them to adulthood. I have two wyverns currently, that have not needed wyvern milk and are currently adults rn. Though it might look like their food levels are dangerously low, do not stress out much, Bc they will survive( I have all my world multipliers at default), I had to walk one to imprint and the other I had to pet it