The ability of cats to see in darkness gives them the special ability to hunt at night. It’s quite normal for a cat to catch a moth midair. It’s also normal for a pet owner to find their cat lying comfortably on their bed when waking up in the morning.
Domestic cats are often active as their owners sleep. They have nocturnal hunting tendencies that are attributed to their great night vision. Thus, cats are able to hunt efficiently during day and night.
Just like the wild felines who often hunt in the jungle only to be given away by their beautiful, glowing eyes, domestic cats behave the same way. The way cats view the world is what determines the kind of sleeping pattern and behavior they adopt.
Felines have a unique and beautiful eye structure that assist them in seeing in darkness. The size and shape of the pupils and the glowing irises contribute significantly to their night vision abilities.
In case you’ve been wondering why the pupils of a cat tend to look like some sort of a straight line in daytime but expand at night to appear like saucer-sized shapes, then get ready to learn why that happens in this article.
The difference in the pupils is all about the lighting amount that a cat needs to see. For instance, the vertical appearance of a cat’s pupils in daytime allows different levels of lighting to enter through different sections of its lens, thereby constricting to assist in focusing.
However, during the night, the pupils dilate to be bigger in size. While this tends to make the vision a bit blurry, it makes it possible for more lighting to pass through the eyes.
The dilated pupil of a domestic cat can be as much as 135-300 times bigger than its constricted size. The human pupil, which is circular in shape, can only expand 15 times in size at night.
Thus, the pupils of a cat expand more than those of a human, thereby allowing more light to pass through the eyes.
While cats boast of having better vision during the night than human beings, they still require some lighting to see properly at night. As light passes through the eye, light rays usually hit the eye retina.
The retina is a form of a layer comprising of tissues that house photoreceptor cells. It’s situated at the back section of an eye. Both humans and cats have a retina with similar functions.
The retina comprises of two photoreceptors which are the cones and rods. The function of the cones is perceiving day vision and color whereas the role of the rods is to assist in peripheral vision, night vision, and sensing motion.
Dogs and cats have a higher number of rods when compared to cones. On the contrary, the human eye has more cones than rods. The higher number of rods in cats gives them better vision in poorly lit environments, especially at night. They only need about 1/6 of lighting that humans need for vision.
The larger number of rods in cats help them to hunt effectively at night despite having the problem of nearsightedness. If the human eyesight is rated 20/20, that of can cat would be around 20/80 on the higher side and 20/100 on the lower side.
For instance, a human being can be 4-5 times far away from an object to spot it in detail, but a cat needs to be closer to the object to spot it in detail. Basically, the vision of cats is blurry when compared to that of human beings.
However, cats are better in sensing changes in lighting and subtle motion. For example, cats can notice moving shadows better than humans, something that assists them in nocturnal hunting.
The eye also has a reflective kind of membrane known as a tapetum. It’s located behind the eye’s retina. Its role is to enhance the light perceived by the rods. The tapetum is also responsible for the glow seen in cats’ eyes in the darkness.
The tapetum, which is the yellowish-greenish shining part of the eyes of a cat is what makes it require less lighting to see in darkness than humans.
It reflects light such that the perceived details hit the retina cells twice whereas in the human eye, the details perceived hits the retina just once.
The reflection in a cat’s eye is the yellowish-greenish reflection you get to see whenever light rays shine in their eyes rather than the reddish reflection seen in the human eye.
Other animal species that hunt or move about during the night, including horses, cattle, dogs, and deer also have the reflective tapetum in their eyes.
On the contrary, some primates and all humans don’t have a tapetum. Thus, when you happen to notice an iridescent eye shine when camping, you’d want to be careful of the animal hanging around.
Here is an interesting Ted-Ed video on how animals actually see in the dark: