Cat senses

Cat senses are adaptations that allow cats to be highly efficient predators. Cats have acute sight, hearing and smell, and their sense of touch is enhanced by long whiskers that protrude from their heads and bodies. These senses allow cats to hunt effectively in dim light or at night.

ight

Testing indicates that a cat's vision is superior at night in comparison to humans, and inferior in daylight. Cats, like dogs and many other animals, have a "tapetum lucidum", which is a reflective layer behind the retina that reflects light that passes through the retina back into the eye. [cite journal |author=Braekevelt CR |title=Fine structure of the feline tapetum lucidum |journal=Anat Histol Embryol |volume=19 |issue=2 |pages=97–105 |year=1990 |pmid=2240589 |doi=10.1111/j.1439-0264.1990.tb00892.x] While this enhances the ability to see in low light, it appears to reduce net visual acuity, thus detracting when light is abundant. In very bright light, the slit-like iris closes very narrowly over the eye, reducing the amount of light on the sensitive retina, and improving depth of field. The tapetum and other mechanisms give the cat a minimum light detection threshold up to seven times lower than that of humans. Variation in color of cats' eyes in flash photographs is largely due to the reflection of the flash by the tapetum.

Average cats have a visual field of view estimated at 200°, versus 180° in humans, with a binocular field (overlap in the images from each eye) narrower than that of humans. As with most predators, their eyes face forward, affording depth perception at the expense of field of view. Field of view is largely dependent upon the placement of the eyes, but may also be related to the eye's construction. Instead of the fovea which gives humans sharp central vision, cats have a central band known as the visual streak. [cite journal |author=Hughes A |title=A quantitative analysis of the cat retinal ganglion cell topography |journal=J. Comp. Neurol. |volume=163 |issue=1 |pages=107–28 |year=1975 |pmid=1159109 |doi=10.1002/cne.901630107] Cats can see some colors, and can tell the difference between red, blue and yellow lights, as well as between red and green lights. [cite journal |author=Schneider H, Beller FK |title=The Spectral Sensitivity of Dark- and Light-adapted Cat Retinal Ganglion Cells |journal=Journal of Neuroscience|language=English |volume=13 |pages=1543–1550 |year=1993 |url=http://www.jneurosci.org/cgi/reprint/13/4/1543] Cats are able to distinguish between blues and violets better than between colours near the red end of the spectrum. [ [http://www.kittyshow.com/x_cat_vision_color.htm Cat Vision and How Cats See ] ] [ [http://www.cathealth.com/CatEyes.htm Veterinary Topics: Feline Vision ] ]

Cats have a third eyelid, the nictitating membrane, which is a thin cover that closes from the side and appears when the cat's eyelid opens. This membrane partially closes if the cat is sick; although in a sleepy, content cat this membrane is often visible. If a cat chronically shows the third eyelid, it should be taken to a veterinarian for evaluation.

Unlike humans, cats do not need to blink their eyes on a regular basis to keep their eyes lubricated (with tears). Unblinking eyes are probably an advantage when hunting. Cats will, however, "squint" their eyes, usually as a form of communication. Cat owners can often entice their pets to squint or even fully close their eyes just by talking to them in a soothing or pleasing manner. Many cats will also squint in response to seeing their owners squint. When a cat does blink, it is a slower blink than in humans, so it will typically blink one eye at a time so it can still see from the other eye. When the cat is looking at someone while doing this, it gives the impression that the cat is winking at them.

Cats have a wide variation in eye color, the most typical colors being golden, green and orange. Blue eyes are usually associated with the Siamese breed, but they are also found in white cats and kittens. It is a common misconception that all white cats with blue eyes are deaf. This is not true, as there are many blue-eyed cats with perfect hearing. However, white cats with blue eyes do have slightly higher incidences of genetic deafness than white cats of other eye colors. [cite journal |author=Geigy CA, Heid S, Steffen F, Danielson K, Jaggy A, Gaillard C |title=Does a pleiotropic gene explain deafness and blue irises in white cats? |journal=Vet. J. |volume=173 |issue=3 |pages=548–53 |year=2007 |pmid=16956778 |url=http://linkinghub.elsevier.com/retrieve/pii/S1090-0233(06)00169-9 |doi=10.1016/j.tvjl.2006.07.021] White cats having one blue and one other-colored eye are called "odd-eyed" and may be deaf on the same side as the blue eye. [cite web|url=http://www.messybeast.com/whitecat.htm|title=White Cats, Eye Colours and Deafness|lastname=Hartwell|firstname=Sarah|accessdate=2006-09-05] This is the result of the yellow iris pigmentation rising to the surface of only one eye, as blue eyes are normal at birth before the adult pigmentation has had a chance to express itself in the eye(s).

Hearing

Humans and cats have a similar range of hearing on the low end of the scale, but cats can hear much higher-pitched sounds, up to 64 kHz, which is 1.6 octaves above the range of a human, and even 1 octave above the range of a dog. [ [http://www.lsu.edu/deafness/HearingRange.html Strain, G.M., How Well Do Dogs and Other Animals Hear?] ] When listening for something, a cat's ears will swivel in that direction; a cat's ear flaps (pinnae) can independently point backwards as well as forwards and sideways to pinpoint the source of the sound. Cats can judge within three inches (7.5 cm) the location of a sound being made one yard (approximately 91 cm) away—this can be useful for localizing prey, etc.

mell

A domestic cat's sense of smell is about fourteen times as strong as a human's.cite web | url=http://cats.about.com/cs/felineanatomy/a/catsnose_scent.htm | title=The Nose Knows | publisher=About.com | accessdate=2006-11-29] Cats have twice as many smell-sensitive cells in their noses as people do, which means they can smell things humans are not even aware of. Cats also have a scent organ in the roof of their mouths called the vomeronasal (or Jacobson's) organ. When a cat wrinkles its muzzle, lowers its chin, and lets its tongue hang a bit, it is opening the passage to the vomeronasal. This is called "gaping", "sneering", "snake mouth", or "flehming". Gaping is the equivalent of the Flehmen response in other animals, such as dogs, horses and big cats.

Touch

A cat has about twenty-four movable vibrissae ("whiskers"), in four rows on each upper lip on each side of its nose (some cats may have more), in addition to a few on each cheek, tufts over the eyes, bristles on the chin, the cat's inner "wrists", and at the back of the legs. [ [http://www.moggies.co.uk/html/whiskers.html Cat's Whiskers ] ] The Sphynx (a nearly hairless breed) may have full length, short, or no whiskers at all.

Vibrissae aid navigation and sensation. The upper two rows of whiskers can move independently from the lower two rows for even more precise measuring. Whiskers are more than twice as thick as ordinary hairs, and their roots are set three times deeper than hairs in a cat's tissue. Richly supplied with nerve endings at their base, whiskers give cats extraordinarily detailed information about air movements, air pressure and anything they touch. Vibrissae possess exquisite sensitivity to vibrations in air currents. As air swirls and eddies around objects, whiskers vibrate too. Whiskers may detect very small shifts in air currents, enabling a cat to know it is near obstructions without actually seeing them. Cats use messages in these vibrations to sense the presence, size, and shape of obstacles without seeing or touching them.

Whiskers are also good hunting tools. The structure of the brain region which receives information from the vibrissae is similar to that found in the visual cortex, suggesting that the nature of the cat's perception through its whiskers is similar to that via its vision. [ [http://jn.physiology.org/cgi/content/abstract/40/5/997 Somatotopic projections of mystacial vibrissae on cerebral cortex of cats] , Journal of Neurophysiology, Vol 40, Issue 5, pp. 997–1014, 1977.] [ [http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1353593 Properties of different functional types of neurones in the cat's rostral trigeminal nuclei responding to sinus hair stimulation] , J Physiol. 1977 October; 272(1): 57–84] [ [http://www3.interscience.wiley.com/cgi-bin/abstract/109689064/ABSTRACT?CRETRY=1&SRETRY=0 Mystacial vibrissae representation within the trigeminal sensory nuclei of the cat] , The Journal of Comparative Neurology Volume 253, Issue 1, Pages 121–133,
9 October 2004.] [ Haight, J. R.: The general organization of somatotopic projections to SII cerebral neocortex in the cat. Brain Res. 44: 483–502 (1972). ] Stop motion photography reveals that at the moment a cat's prey is so close to its mouth to be too near for accurate vision, its whiskers move so as to form a basket shape around its muzzle in order to precisely detect the prey's location. [ [http://www.floridaconservation.org/panther/handbook/natural/relation.html Cat Traits] Floridaconservation.org ] [ Sunquist, M. & F. Sunquist. 2002. Wild Cats of the World. Univ. Chicago Press.] A cat whose whiskers have been damaged may bite the wrong part of a mouse it's attacking, indicating that signals from these delicate structures provide cats with vital information about the shape and activity of its prey — interestingly, whiskers also help cats detect scents. fact|date=October 2008

It is thought that a cat may choose to rely on the whiskers in dim light where fully dilating the pupils would reduce its ability to focus on close objects.

Whiskers are also an indication of the cat's attitude. Whiskers point forward when the cat is inquisitive and friendly, and lie flat on the face when the cat is being defensive or aggressive. fact|date=August 2008

Whiskers can also be a bother to a cat, especially when the cat tries to eat food out of a bowl. The end of the whiskers touching the side of the bowl transfer irritating sensations to its brain, making it hard for it to continue eating. fact|date=August 2008

Taste

The cat family was shown in 2005 to lack the T1R2 protein, one of two required for function of the sweetness sensory receptor; a deletion in the relevant gene ("Tas1r2") causes a shift in the genetic reading frame, leading to transcription stopping early and no detectable mRNA or protein produced. [cite journal
last = Li
first = Xia
coauthors = Weihua Li, Hong Wang, Jie Cao, Kenji Maehashi, Liquan Huang, Alexander A. Bachmanov, Danielle R. Reed, Véronique Legrand-Defretin, Gary K. Beauchamp, Joseph G. Brand
title = Pseudogenization of a Sweet-Receptor Gene Accounts for Cats' Indifference toward Sugar
journal = PLOS Genetics
volume = 1
issue = 1
publisher = Public Library of Science
date = July 2005
url=http://genetics.plosjournals.org/perlserv/?request=get-document&doi=10.1371/journal.pgen.0010003
doi = 10.1371/journal.pgen.0010003
accessdate = 2006-11-08
pages = e3 ] The other protein, T1R3, is present and identical to that of other animals, and the relevant taste buds are still present but inactive. Such a genetic marker found in the entire family and not other animals must be the result of a mutation in an early ancestor; as a deletion mutation it could not revert, and thus would be inherited by all descendants, as the evolutionary tree branched out. Most scientists now believe this is the root of the cat family's extremely specialized evolutionary niche as a hunter and carnivore. Their modified sense of taste would cause them to some degree to ignore plants, a large part of whose taste appeal derives from their high sugar content, in favor of a high-protein carnivorous diet, which would still stimulate their remaining taste receptors.

References