Whale Senses
Sight
Whales are required to spot prey and predators in the murky deep waters
of the ocean. These depths are not illuminated by the sun to any significant degree
(depending, of course, on the depth). Whales have an adapted sense of sight to allow
for them to course through the waters without being hindered by dangers or obstacles.
When underwater, whales can see approximately 35 feet (10.7m) ahead of themselves.
When leaping out of the water, whales are more near sighted as the air density and
pressure is significantly different to that of water. The eyeball is not completely
round, but flattened from front to back, with a compressed cornea. This decrease
in curvature means that the refractive index (the degree to which the speed of light
is reduced within the medium) is lowered. The reflective layer behind the retina
(called the tapetum lucidum) reflects the limited amount of light onto the retina
twice, increasing the quality of the picture seen. Whales have ducts on the corner
of each eye that secrete an oily lubricant to clean the eyes. There are no tear
ducts. Because of the depths to which a whale dives, there is an enormous amount
of pressure placed on the eyeballs (as there is on the rest of the organs too),
and these are designed to withstand such pressure. Whales have more rods than cones
in their eyes, which means that their ability to see a rich diversity of colours
is compromised for the ability to gather more low-intensity light.
Smell
There is contradictory research on the sense of smell in whales. While some believe
that whales are able to smell to a very limited degree, others state that adult
whales lose all function of the olfactory nerves.
Sound
Because the vision of whales is compromised by the low light levels and
murkiness of the ocean, their excellent sense of hearing is very important. Their
hearing is particularly acute in terms of low frequency sounds. Boat engines are
audible, and whales have even been known to react to the click of an underwater
camera.
Baleen whales do not have pinnae, or outer ear flaps (as humans do), to direct noise
into the canal. Their outer ear is, in fact, plugged shut. They have only an outer
ear canal, which leads directly to a tympanic membrane, as the eardrum is known.
This vibrates when noises are received into the canal and causes the 3 bones inside
the ear (the malleus, incus and stapes) to vibrate as well. As the stapes rocks
back and forth, it causes wavelike motions in the fluid of the inner ear’s sac.
Pitch and volume is determined by the way and extent that the way fluid moves over
hairlike cells, as is the case of humans. The further over the hairs are bent, the
more intense the sound perceived. These take some time to revert back to their upright
position (as is the case when we listen to very loud music), and consideration should
be taken regarding the noises that we inflict on these animals, and the long-term
effects these may have.
Toothed whales hear through their lower jaw, where a layer of acoustic fat transmits
sound to the middle ear, which is filled with fluid and foam. This foam obviously
contains air too, and this is what assists the whales to be able to discern the
direction from which the sound is coming.
Taste
As taste is so closely related to smell, there also exists differing opinions
regarding the extent to which whales can taste and the importance of this sense.
There is an active part of the brain that discerns taste, and whales do have taste
buds, so they are able to sense different tastes to some extent.
Touch
Whales have a relatively thin skin. This is rich is blood vessels and nerves,
making them very sensitive to touch. It is for this reason that whales value touching
one another as an important means of communication.
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