Does being a bigger dog equate having a bigger heart? It certainly looks like it because both the cats have placed complete faith into the dog. They can be seen resting comfortably on its warm, brown fun, knowing full well that it has no ill intentions. Although the dog can swallow them completely should it desire, but it has the intellectual capacity to suppress the predatorial instinct.
After all, this is what separates the good dogs from the bad ones. The ability to put aside your differences in favor of what the other species has to offer as a cat. They are after all warm and cuddly buddies that the dog can use as a blanket should the time come for that. For now, its time to lend its fur to the little creatures and let them slumber in peace.