After years of struggle, the two of them decided it would be better to become good friends instead of enemies. They sleep over each other, play with each other and share the same food. It must have a tiresome day which has allowed them to become this sleepy. There used to be a time when they would snap their jaws at each other's flesh in the hopes of inflicting harm.
They would halt their violent activities once the owner enters into the picture. But the owner would see right through their tricks, and would admonish them for their violent tendencies. After a few instances of disciplining by their master, they realized it would be so much better to just get along. They are the best of friends today, inseparable and insurmountable against the worst of admonition.