Rabbits have a highly developed sense of smell, about 20 times greater than the human sense of smell (they have about 100 million olfactory cells compared to 40-60 million in humans).
The sense of smell is used to search for food, recognize members of the group, identify predators and to regulate sexual activity.
Rabbits are obligate nasal breathers. The nostrils have rapid movements (20-120 per minute) that cease when the rabbit is relaxed or asleep (or in conditions of discomfort). These continuous movements have the function of increasing the deposition of particles in the olfactory region.