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]