2. Cetacean Ears
65
FIGURE 2.4. Middle ear/tympano-periotic complex architecture. A mid-modiolar
cross-section is shown of the right tympano-periotic complex in situ-in a bowhead
whale (Balaena mysticetus) late-term fetus. The ear is shown in its natural orientation in the whale's head. Characteristic mysticete features include a dense hemispheric tympanic (t); a triangular periotic (p); and a blunt, membranous tympanic
membrane (glove finger, gf), which is relatively short in this species. The short arrows
indicate the tip and tympanal junctures of the glove finger. Trigeminal nerve (tn)
bundles traversing the corpus cavernosum (cc) are indicated by long arrows. The
only ossicle visible at this level is the malleus (m). a, Apex; b, basal turn of the
cochlea; me, middle ear cavity; nf, auditory nerve fibers; sq, squamosal; v, vestibule.
(Dr. Daniel Hillman of Louisiana State University School of Veterinary Medicine
provided access to the specimen and prepared the section.)
studies of both African and Indian elephants show unequivocally that elephants respond to infrasound (Payne et al. 1986; O'Connell et al. 1997), but
the published audiogram of an Indian elephant indicates best sensitivity
is near 1kHz with fairly steep decline in thresholds for all higher and
lower frequencies and no indication of any infrasonic hearing (Heffner and
Heffner 1980). O'Connell et al. (1997) showed that elephants produce
seismic range vocalizations and use body movements to induce Rayleigh
waves, a type of ground surface wave that travels at three-quarters the
65
FIGURE 2.4. Middle ear/tympano-periotic complex architecture. A mid-modiolar
cross-section is shown of the right tympano-periotic complex in situ-in a bowhead
whale (Balaena mysticetus) late-term fetus. The ear is shown in its natural orientation in the whale's head. Characteristic mysticete features include a dense hemispheric tympanic (t); a triangular periotic (p); and a blunt, membranous tympanic
membrane (glove finger, gf), which is relatively short in this species. The short arrows
indicate the tip and tympanal junctures of the glove finger. Trigeminal nerve (tn)
bundles traversing the corpus cavernosum (cc) are indicated by long arrows. The
only ossicle visible at this level is the malleus (m). a, Apex; b, basal turn of the
cochlea; me, middle ear cavity; nf, auditory nerve fibers; sq, squamosal; v, vestibule.
(Dr. Daniel Hillman of Louisiana State University School of Veterinary Medicine
provided access to the specimen and prepared the section.)
studies of both African and Indian elephants show unequivocally that elephants respond to infrasound (Payne et al. 1986; O'Connell et al. 1997), but
the published audiogram of an Indian elephant indicates best sensitivity
is near 1kHz with fairly steep decline in thresholds for all higher and
lower frequencies and no indication of any infrasonic hearing (Heffner and
Heffner 1980). O'Connell et al. (1997) showed that elephants produce
seismic range vocalizations and use body movements to induce Rayleigh
waves, a type of ground surface wave that travels at three-quarters the