Sows sing to their piglets while they are suckling.
Pigs are very social animals and care lovingly for their litter.
If they can be born outside, the pregnant mother pig digs a homely hollow and fills it with soft branches, grass and leaves before she gives birth to her litter. In it, the litte ones are born and after a few minutes they start looking for the teat to slurp tasty breast milk.
Their mother even sings them while they suckle on her. At least it sounds like it in the ears of the piglets. It consists of grunts at different pitches and intervals.