While it isn't direct evidence, the relative size of the auditory (tympanic) bulla in relation to the skull is a good indication of the importance of sound to a species. In animals with sensitive hearing and diminutive external ears, a large auditory bulla is present. The auditory bulla increases hearing sensitivity in at least two ways; by acting like a resonating chamber, increasing the vibration on the tympanic membrane (eardrum), and because it is directly connected to the malleus (hammer) by a tiny ligament, which increases the vibration on the tiny bone in the inner ear. The shape of the auditory bulla in ferrets apparently increases sensitivity to specific frequencies of sound--quite an advantage when stalking animals in underground lairs. The presence of a large auditory bulla is significant evidence of the importance of sound to a ferret. http://homepage.mac.com/billgruber/fml/hearing2.html Ferrets are extremely responsive to auditory stimulation, and are trained better to sounds than to visual commands (clickers, tones, and whistles are very effective). Sound enrichments can include everything from natural sounds (waterfalls, rain, insects, birds), music (anything except country western: no one should be forced to listen to THAT), recorded voice, and wind chimes. Part of an auditory enrichment can include tactile enrichment as well; sound vibrations can be part of the sound experience. Wizard is normally an extremely energetic ferret--one that can hardly hold still enough to pose for a photo. Sitting a speaker on its back, covering it with a dark cloth, cranking up the bass (but not so loud to harm delicate ferret ears), and playing a cut from "Ride the Lightning" got his attention. Wiz lay with his stomach in contact with the speaker for more than five minutes, all the while looking around trying to see who was tickling him. Finally, he shot off the speaker and dashed around the room for a good half hour, periodically returning to the speaker "to check it out." http://homepage.mac.com/billgruber/fml/hearing.html Bob C [Posted in FML issue 4213]