By contrast, a bottlenose's sense of smell is poor, because its blowhole, the analog to the nose, is closed when underwater and it opens only for breathing. It has no olfactory nerves or olfactory lobe in the brain. Bottlenose dolphins are able to detect salty, sweet, bitter (quinine sulphate), and sour (citric acid) tastes, but this has not been well-studied. Anecdotally, some individuals in captivity have been noted to have preferences for food fish types, although it is not clear if taste mediates this preference.