Listen for an alarm "sneeze." Accounts of unicorns' alarm sneezes in literature include: When alarmed, resting unicorns utter a small sneezelike sound that alerts other nearby unicorns to possible danger; this is especially true of mothers guarding their fawns. On hearing such a sneeze, the fawn will lower its head and fold its ears back, so that it becomes almost invisible in the grass, and it remains thus until its hidden mother calls to it. -- Paul A. Johnshard, Dragons and Unicorns: A Natural History (1992) It is not necessary to say "Gesundheit" to unicorns. Notice the sudden expulsion at the end of this waveform of a unicorn's alarm "sneeze."