In a group of pet rats, social hierarchy refers to the ranking system that determines the dominant and submissive roles among the rats. Rats establish their hierarchy through various behaviors such as grooming, scent marking, chasing, and vocalizations. Dominant rats typically have priority access to resources like food, shelter, and mates, while submissive rats may display submissive behaviors such as avoiding eye contact or backing down during interactions. Maintaining a stable social hierarchy helps reduce conflicts and ensures order within the group.