Senses of Beluga Whales

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. In comparison, the average hearing range for humans is about 0.02 to 20 kHz. In a study using two trained beluga whales in an open-ocean environment, scientists found that the sensitivity of a beluga's hearing does not change with depth. 3. Sound reception. • Most sound reception probably takes place through the lower jaw. A beluga may also receive sound through soft tissue and bone surrounding the ear. • 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. • 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. Belugas have a tiny external ear opening a few inches behind each eye.

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EYESIGHT

1. Beluga whales have acute vision both in and out of the water. Belugas have excellent eyesight in and out of the water. • A beluga's eye is particularly adapted for seeing in water. In air, certain features of the lens and cornea correct for the nearsightedness that results from the refraction (bending) of light rays as they go from water to air. • 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. (Rod cells respond to lower light levels than cone cells do.) As with other whales, belugas lack short wave-length sensitive visual pigments in their cone cells indicating a more limited capacity for color vision than most land mammals. 2. Glands at the inner corners of the eye sockets secrete an oily, jelly-like mucus that lubricates the eyes and washes away debris. This tear-like film may also protect the eyes from infective organisms.

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TACTILE

1. Studies on belugas in zoological environments indicate that they seek out physical contact with other belugas.

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TASTE

1. Biologists have noted sensory areas in beluga whale mouths that may function in taste.

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SMELL

1. Olfactory lobes of the brain are absent in all toothed whales, suggesting that they have no sense of smell. Like other species of toothed whales, the brain of a beluga does not have olfactory lobes indicating that they have no sense of smell.