Do you know why your cat or dogs eyes glow in the dark? Like humans,
animals have a layer of tissue in the back of the eyes called the retina that captures everything we see. However, animals such as the cat, dog, fox &
other predatory animals’ posses a second layer of tissue behind the retina known as the tapetum lucidum. This second layer of tissue gathers incoming
light that is then reflected like a mirror back to the photo receptors also
known as, rods & cones/retinal cells. As this second layer
of tissue is so sensitive, every scrap of light that enters the eyes is then utilized. However, this
will not be effective in complete darkness. In total darkness, such
animals must rely on their good sense of smell, hearing & their amazing whiskers. It is fact that the human
eye absorbs far less light than these animals. Because of this difference, such animals can detect movements &
objects in semi-darkness far better than the human eye. Like other semi-nocturnal or nocturnal animals the eyes of a
cat, dog or other animals a like are far more attuned to seeing in dim light as they need only one-sixth of
light to see detail of movement & shape of objects in dim light conditions.
The pupils: Like the fox & as cat owners will notice, their cat posses diamond shaped pupils that shut
a lot firmer to form a vertical slit in very bright light in order to prevent dazzling. This is important
when a cat ventures out in very bright sunlight & it is vital to such animals that
rely very much on their night vision. As the vertical slit helps control the amount of light that
enters the eyes, it therefore helps to protect the sensitive membrane of the back of the eyes. It is apparent
that such animals with diamond shaped pupils use their eyelids to further reduce intense light such as very
bright sunlight. The more intense the light the more the pupils will form the vertical tight slit. In return the less
light that enters the eyes the reverse effect happens in that the pupils will dilate to black pools (wider
pupils) like other animals & humans eyes do. However, not all predatory animals such as lion’s posses’
diamond shape pupils & therefore they posses’ horizontal pupils like humans, dogs & other animals.
Other uses of the eyes: Many animals use their eyes as a tool to communicate with each other by using different signals with
the movement of their eyes in different directions. Some cat owners may notice a sudden dilation with
in their cats eyes when a hungry cat is having their food put in front of them. The diamond shaped pupils will suddenly
change into dark pools of feline expectation, (wide pupils) just like they do in the dark. Further studies show this
sudden dilation will happen with in a split second & the pupils increase to around four
or five times its previous size. This sudden change is related to the cats mood-signalling system but this is only one
way in which the eye expression changes. The most basic eye change depends on the strength of light any
time of day.
The proximity of a viewed scene affects the pupils in that the closer an object is,
the more it constricts the pupils. The further an object is the pupils will be expanded a little. This change also interferes
with our reading of the mood signals coming from the eyes. Further more, there are two other types of mood-changes, the pupils
will enlarge when a cat or other animal a like sees something both pleasant & or threatening. The
only way to recognise this sudden change is when there is no change in the strength of light or proximity of an
object then the animal may be experiencing strong emotions. Such emotional arousals may be the arrival
of their food or an unpleasant arrival of an unwanted aggressive rival that may try to be a threat. In
both cases the pupils will enlarge more than usual.
Many predators rely very much on their binocular vision when hunting. A
cat will often sway its head from side to side in a steady motion to locate the exact spot where
the prey is before pouncing on & capturing the unlucky victim. With out the cat using such
action & using its vision in this way catching the prey could fail.
Colour vision: Many people believe an animal such as a cat or dog is colour blind & can only see black & white.
This has been proved not to be the case but sure enough such animals may not see colour like the human eye. Rods (retinal
cells) are useful for seeing black & white in dim light & cones (retinal cells) are for colour vision. It
is understood that a cat can distinguish colours but not apparently with much finesse. In more recent tests since
the 1940s it has so far been proved that a cat can see the difference between, red & blue, red & green, red &
grey, green & blue, green & grey, blue & grey, yellow & blue & yellow & grey. It is still not yet understood
if a cat can tell the difference in other pairs of colour. There is some suggestion a cat may be able to tell
the difference between red & yellow. It is felt that colour is not as important to cats’ dogs or many
animals as is it is for humans. Colour vision may differ between different animals like dogs & cats.
How well can an animal hear? Many animals have much the same low pitch range of hearing as humans. However, such animals
have a far better ability to hear at a high pitch range. A young persons hearing can range from about,
30,000 cycles per second. As we get a little older, it decreases to around, 20,000 cycles per second. By the time
a human is of retiring age it decreases down to a bout 12,000 cycles per second. As for animals they have
a much higher range of about 35,000 to 40.000 cycles per second. Cats have an even higher range of about 60,000-100,000 cycles
per second. Like cats & other predators, they largely rely on their hearing when hunting. Such predators
have the ability to hear high pitched squeaks of rodents, bats, birds & other prey. The ability to hear sound
at such a high range would be totally inaudible to the human ear.
A dog or cat has the ability to recognise the footsteps of their owner from
long distances & they to can define the engine of their owners’ vehicle.
Hearing is one of the most important senses for many animals. Hearing is the
most highly developed sense of some animals such as rabbits & hare. Pricking of the long ear flaps of a
rabbit or hare is important as this helps to catch the faintest of sound that will warn them of danger from predators. The
long ear flaps gather sound waves in a similar way to television or radar dishes that gather electronic signals rather than
sound. Such animals will raise their body & swivel their highly sensitive ears to improve the reception of sound. Other
animals’ ears act in much the same way for their own purpose. Animals often make signals with their ears in
order to communicate with each other.
How sensitive are the whiskers? It
is true that the whiskers act as feelers in that an animal can tell if it is navigating between wide &
narrow gaps. With out doubt & indeed, this is beneficial in complete darkness but there is more
to how the remarkable whiskers are used as they operate as air-current detectors. This is possible as
they can detect the slightest changes in the air when the animal is passing solid objects without having
to touch them as signals are transmitted from the whiskers to the brain. The whiskers are
indeed a vital tool for a predator. A predator such as a cat will usually make a clean kill of their
prey both day & night but if the whiskers are damaged, a clean accurate kill can only be performed in the daylight.
The reason being is; a predator with damaged whiskers is likely to misjudge the point of the body to kill
in the dark as they are likely to bite into the wrong part. It is therefore easier for a predator
with damaged whiskers to make an accurate kill bite in the daytime as their daytime vision will compensate. Healthy whiskers
are highly effective in the dark as they act as a guidance system as the predator is able to locate the correct
part of the outline of the prey's body to locate the nape of the neck to kill the unfortunate victim. The tips of
the whiskers act in much the same way as the fingertips of a blind person reading braille in that the whisker
tips can read the outline of the body of the prey. This is done in an astonishing split second
in order to find the nape of the prey's neck. Some photographic evidence shows how a cat carrying
a small rodent in its jaws also reveals how its whiskers are partially wrapped round the prey. The whiskers will transmit
any information about the prey to detect if there is any movement assuming the prey is still
alive. Since many predators are predominantly nocturnal hunters (hunters by night), their whiskers are a very important
tool in order to benefit their survival.
The whiskers are very thick & toughened hairs that are situated on ether
sides of the top jaw towards the nose.
How sensitive is the nose? Many animals rely heavily on their amazing sense of smell for many reasons
as their sense of smell is far more advanced than that of humans. MORE INFO SOON.