A. Hearing.
1. Beluga whales have a well-developed, acute sense of hearing. The auditory cortex of the brain is highly developed.
2. A beluga whale can hear sounds in the range of 1.2 to 120 kHz, with a peak sensitivity of about 10 to 75 kHz (Fay, 1988). The average hearing range for humans is about .02 to 20 kHz (Considine, 1976).
3. Sound reception.
a. Most sound reception probably takes place through the lower jaw. A beluga may also
receive sound through soft tissue and bone surrounding the ear.
b. The fat-filled lower jawbone appears to conduct sound waves through the jaw to bones
in the middle ears. The lower jaw of toothed whales broadens and is hollow at the base,
where it hinges with the skull. Within this very thin, hollow bone is a fat deposit that
extends back toward the auditory bulla (earbone complex). Sounds are received and
conducted through the lower jaw to the middle ear, inner ear, and then to hearing centers
in the brain via the auditory nerve.
c. A beluga has small external ear openings, a few inches behind each eye. Each opening leads to a reduced ear canal and an eardrum. Some scientists believe that beluga whales receive sounds through these openings. Other scientists believe that a beluga whale's external ear openings are nonfunctional.
B. Eyesight.
1. Beluga whales have acute vision both in and out of the water (Herman, 1980).
a. A beluga's eye is particularly adapted for seeing in water. In air, certain features
of the lens and cornea correct for nearsightedness (Herman, 1980).
b. A beluga's retinas contain both rod and cone cells, indicating that they may have the ability to see in both dim and bright light (Herman, 1980). (Rod cells respond to lower light levels than cone cells do.) The presence of cone cells suggests that belugas may be able to see color, although this ability hasn't been documented.
2. Glands at the inner corners of the eye sockets secrete an oily, jellylike mucus that lubricates the eyes and washes away debris. This tearlike film may also protect the eyes from infective organisms.
C. Tactile.
Studies on belugas in zoological environments indicate that they seek out physical contact with other belugas (Ridgway and Harrison, 1981).
D.
Biologists have noted sensory areas in beluga whale mouths that may function in taste (Haley, 1986).
E. Smell.
Olfactory lobes of the brain and olfactory nerves are absent in all toothed whales, suggesting that they have no sense of smell.
Adaptations for an Aquatic Environment
SeaWorld/Busch Gardens Animal Information Database
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