What do you think of when you look at your sweet, soft fur darling curled up sleeping in your lap? A beautiful creature as graceful, lithe and agile as a dancer? Look again. This time, do you see a full communication system, versed in verbal and nonverbal abilities, from nose to tail? Now look once more. Do you see a stealthy, skillful predator?
The answer to all three of these questions should be “yes.”
Every facet of the feline body fuses form and function to create an obligate carnivore, a fearsome predator designed to hunt and eat prey and utilize the essential nutrients from it. This natural design cannot be undone and cats cannot choose to be vegetarian any more than we can choose our biological parents. The predatory behaviors activate within the first 52 days of life.
For the thousands of years that cats have shared our home and hearts, and with all that we know, we’re still amazed, mystified, and at times, unsure about how the graceful, stealthy, agile and elegant feline design functions.
The Feline Skeleton
The cat’s skeleton is composed of approximately 244 bones, about 40 more than humans. The difference in number primarily comes from how many tail bones an individual cat has. The hard skeleton provides support and protection of soft tissues, like the internal organs, yet is lightweight for springing and is extraordinarily flexible.
In addition to bones, other structures include ligaments, the connective tissue which holds bones together (where two bones meet is called a joint); cartilage, the padding between joints; and tendons, connecting bone to muscle. Together, these elements form a graceful, agile and speedy predator.
One of the most fascinating aspects of the cat’s physical structure is seen in its slinky strut. Watch a cat walk and you’ll see how the shoulders alternatively dip, giving it a beautiful slinky stride. This is because the cat’s small collarbone, or clavicle, is not fused to the skeleton. Rather, it is connected to the chest by muscle. This structure narrows the deep chest and allows the front legs and feet to stay close together while giving speed, long strides, flexibility and the uncanny ability to get into tight spaces. Notably, some cats have no collarbone at all.
The 30 very flexible vertebrae in the supple spine, and the way the spine attaches to the legs, allow felines to stretch out and lengthen during leaps, compress the spine to curl up in a tiny ball, arch the back and rotate, bend and twist the front half of the body independently from the back half. This ability, combined with the keen sense of balance from the fluid-filled cochlea in the inner ear, enables the righting reflex. The righting reflex is an automatic response of the cat’s nervous system that corrects the orientation of its body when it isn’t in its normal, upright position.
This innate righting reflex turn allows a cat to land on its feet when jumping or falling. As soon as the cat senses disorientation, the head rotates first, followed by the front legs. Then the hindquarters rotate around, and the legs extend out for landing, with the flexible joints acting as shock absorbers. Remember, cats do not always land on their feet and can, and do, sustain injuries from falls.
The vertebrae in a cat’s tail, called caudal vertebrae, are as flexible as the spinal vertebrae. The number of vertebrae varies from cat to cat. Bobtailed cats, such as the Manx of Japanese Bobtail, may have three vertebrae in the tail, while long-tailed cats, like the Siamese, may have up to 28 vertebrae.
Limbs and Digits
A cat’s slender limbs differ in structure and purpose. The front legs are more flexible in rotation, allowing the front paw pads to reach the head and face for grooming. The front legs have elbows, which are hinged backward and slightly bent, but can be locked in place by supporting ligaments and muscles.
Cats have flexible wrists that aid in climbing, throwing prey (or toys) in the air, and curling the paws underneath the body during sleeping.
The less flexible rear legs move forward and backward. The structure of the knee, which opposes the elbow, powerfully propels the cat’s spring in pouncing and running. Felines, like Formula One race cars, are built for speed, not distance.
At the base of those slender legs are fleshy, hairless, sensitive pads which support the feline body and act as shock absorbers. The front paws have five toes each and the back paws have four toes each, for a total of 18 toes. Cats with a genetic anomaly that causes them to have up to eight toes per paw are called polydactyl cats.
A cat’s toes have curved, sharp claws used for scratching, fighting, climbing and gripping. We usually think of the claws as retractable. However, the default state is retracted, meaning the claw is hidden away or sheathed. The claws may stay hidden to avoid excessive wear and tear from walking. The claws are connected to the last toe bone and are exposed when your cat is excited or frightened.
Cats, like dogs, are digitigrades, meaning they walk on their toes and what we call the ball of the foot. Humans walk on the sole of the foot, which makes us plantigrade. The digitgrade posture enables the quick, quiet movement necessary for stealthy predators.
A cat’s gait is unusual in the animal kingdom. Cats walk in a “pacing” gait, moving the front and rear legs on one side of the body, and then front and rear legs on the other side. Camels and giraffes are the only other two animals with this “pacing” gait. When a cat breaks into a trot or sprint, they use the “diagonal” gait, with diagonally opposing front and hind legs moving in unison, like when you walk and swing your arms.
Feline Ears and Eyes
Cats’ ears help them to maintain balance and signal emotions. Hearing is also one of the cat’s sharpest senses. They can hear sounds too faint for our ears and hear sounds at a much higher pitch than we, or even dogs, can hear. The cat’s hearing range is from 45 to 64,000 Hz.
Like all four-legged animals, cats have cup-shaped ears. These cup-shaped ears have over 32 muscles, enabling them to swivel 180 degrees, as well as move independently of each other to locate the source of a sound.
Sound is the vibration of air. The outer flap of the ear, or pinna, grabs the sound vibration and funnels it down the external auditory canal, the ear canal, to the eardrum, the tympanic membrane. From the ear drum, the three auditory bones, the ossicles, carry the vibration to the snail-shaped cochlea in the inner ear. The cochlea converts the sound into electrical impulses. The auditory nerves carry the impulses to the brain where they are registered as sound.
Upon hearing a sound, a cat’s whole head turns toward it and the eyes focus in, too. The ears also serve as a mood barometer. Upright, forward ears mean a relaxed cat. Swiveling ears signal an interested, listening cat. Ears turned sideways, back or down express agitation. The flatter the ears, the more agitated the cat.
Cats’ eyes are unusually large relative to their body size. In comparison, if our eyes were as large relative to our body size, each eye would measure approximately eight inches in diameter. The large cornea, the part you see when facing your cat, allows more light into the back of the eye. The elliptical shaped pupil acts like venetian blinds to allow more or less light into the eye.
What about those spooky eyes that glow in the dark? That ability comes from a reflective layer of cells in the back of the retina called the tapetum lucidum. When illuminated, these cells reflect light back into the retina and cause the eyes to shine at night. The large number of rods within the retina gives cats their superior nighttime vision.
Cats have a whopping 200-degree field of vision compared with our 180 degrees, enabling them to see practically in all directions except straight behind. For this enhanced field of vision, the cat cannot see objects close up because the muscles that control eye’s lens are weak, making cats farsighted. The optimum viewing distance is a range between seven and 20 feet.
By Sarah Zumhofe