I do think it's a sign that a pig has or is an under-pig, however that can change. My first pig had notches and even a hole in her ear where she had lived with another before (which died), and I don't know what their relationship was like but the two were kept in a tiny hutch and not cleaned out often, so I've been told by the neighbour of the family who kept her. Anyhow stress may have been a factor in this case.
As she was a lone pig when I took her on, I got a friend for her straight away and this friend was a baby. The First pig (the one with the notches in her ears) and her new companion naturally took on dominant elder and submissive baby role, though actually the elder pig mothered the younger, she was a gentle leader.
This first pig eventually became head of a herd of four, of piggies of various ages.
She had probably been an under pig who had risen to leader through circumstance, not really by personality.
None of her underlings had gained any notches to their ears though.
First-pig died, second pig (the previous baby) became head of the herd, and she was a little more assertive but still gentle. |Again no-one gained any ear-notches.
This is a cycle that has continued. Penny, once a baby of the herd and bottom, now leads the sows, again through circumstance. She had seemed very much a natural submissive pig who followed the leader everywhere. After the leader died Penny found her own leadership skills and although again she is a gentle leader I have discovered she can be aggressive if she doesn't like a new-comer. She had always seemed like a follower before...
I do think it can be a sign when the dominance has had to be established between two similar-aged piggies, but circumstances can change, so a notched pig may not necessarily always be happy to be the underling. It's not always a sign of a submissive pig as such, just one who has conceded to it's current position.
What I am saying is, in future introductions this seemingly submissive piggy may decide it's time to be boss.
