Animals must use information about their environment in order to survive. The chemical senses are among the oldest and most basic means to this end, and are present even in the simplest of creatures. Smells provide animals with rich information-critical for nding and selecting their food, avoiding toxic or harmful environments, navigating their path, evading their predators, overcoming their competitors and selecting their mates. Odors guide creatures to potential food sources, and provide critical information about the food’s nutritional value, quality, and whether or not it is safe to consume. Odors allow predators to track their prey, and warn potential prey about the presence of its predator. They guide animals to their conspecics and help them infer intimate details about the identity, sex, genetic background, hormonal state, tness, and health of those individuals, thus serving an important factor in all aspects of social interaction.