Biologists have solved the long-standing scientific mystery of how mice first know to nurse or suckle. This basic mammalian instinct, which could be a key to understanding instinctive behavior more generally, was thought to be triggered by a specific odor (pheromone) that all mouse mothers emit. But the trigger in mice turns out to be a more complicated blend of nature and nurture: a signature mix of odors, unique for each mother, which her offspring learn.

Source: The smell of mom: Scientists find elusive trigger of first suckling in mice