Like invading territory, the leader leads the group to a rival's territory. Except, instead of fighting the main group, they go for the burrow. They must first fight the baby-sitter before getting to the pups. Only the dominant female can kill the pups, to make it just. They can't just kill all the pups in one post, they must leave several posts before they can say the dominant female attacks and kills one/another. Pups don't go up for adoption until one week after they are born, in that time is the time a dominant will attack and likely kill them. Until they are adopted, who ever plays the mother will play the pups.