1. Baleen whales have well developed hearing, which is valuable in the poorly lit ocean environment where vision is less dependable. Portions of the baleen whale brain dedicated to hearing suggest this sense is excellent.
2. Baleen whales probably hear very well in the low frequency ranges but may lack the ability to hear high frequency sounds. Baleen whales react to noises such as boat engines and cameras clicking underwater.
3. Baleen whales have a small external ear opening on each side of the head. Each opening leads to a narrow auditory canal that is completely closed by a waxy substance and reduced to a strand of fibrous connective tissue. The effectiveness of sound reception and hearing through the ear canal is unknown. The middle and inner ear follow the basic mammalian ear structure. More research is needed to determine the exact mechanism for sound reception in baleen whales.
4. A foam surrounds the ear bones. This foam contains air. Air stops sound waves
traveling through water and living tissues. Many scientists believe that this foam
acoustically isolates the ears, enabling a whale to tell from which direction a sound
comes.
B. Eyesight.
1. Because the ocean is often dim, baleen whales have adaptations for vision in low-light conditions.
a. The baleen whale eye is flattened from front to back, and the cornea is less curved. This lowers the refractive index and allows better vision in low-light conditions.
b. A tapetum lucidum, a reflective layer behind the retina, reflects light back to the retina a second time. This takes advantage of what light exists at depth.
2. Baleen whales' eyes are constantly bathed in water. There are no tear ducts, but glands at the outer cornea and eyelids secrete an oily substance that lubricates and cleans the eyes.
3. Baleen whales are nearsighted in air.
4. Retinas of baleen whales' eyes contain mostly rods, cells which gather more low
intensity light. Cone cells, which are responsible for color vision, are much less
abundant.
Baleen whales have sensitive skin, especially on the head and flukes.
The sense of taste has not been well studied in baleen whales. Nerves and the area of
the brain concerned with taste are present. There are taste buds on the base of the
tongue, but their importance is unknown.
Olfactory nerves and bulbs are present in baleen whales during the fetal stage, but they are greatly reduced in the adult brain. Scientists have yet to discover whether such nerves and bulbs are functional.
Adaptations for an Aquatic Environment
SeaWorld/Busch Gardens Animal Information Database
www.seaworld.org / www.buschgardens.org
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