On some occasions we have surely seen a cat at night or in the dark, highlighting the brightness of their eyes, especially when they are focused by some kind of light.
Although it is not uncommon for us, it is likely that at some point we wondered why this glow, That they have their eyes that make them shine that way and if it is of any use to them. In this article, we intend to answer this question.
In fact, it is a question that has aroused the curiosity of man since ancient times, coming to consider cats as the guardians of the night and of the underworld in ancient Egypt because of this peculiarity, among other things. It was believed that the iridescence of his gaze during the night was due to the fact that they saw the truth and even beyond death, and that he kept the world in the sun. But the glow of a cat’s eyes has a scientific explanation, the tapetum lucidum.
Why do cats eyes glow? The tapetum lucidum
The answer to the question of why cats’ eyes glow is none other than the existence of a band of cells located behind the photoreceptors in the eyes of these animals, specifically between the retina and the optic nerve (this could be considered part of the choroid). Called a tapetum lucidum, it acts like a concave mirror inside the eye, causing light to enter the pupil to pass through the retina as it enters the eye and bounces off the screen. like that, the amount of light reflected in the retina increases dramatically and can even be seen from the outside. Technically, it’s not that their eyes shine, but that they reflect outside light.
This allows them to pick up and make the most of ambient light, making it easier for them to move around at night than other creatures and see in the dark until it’s total. Its visual capacity increases considerably and in turn serves as a deterrent to possible attacks.
Tapetum lucidum increases the sensitivity of the stems thirty to fifty times, although that would not be enough for them to see in absolute darkness. In most animals without this adaptation, much of the visual information is lost because the eye does not reflect all of the light that enters the pupil. In the case of cats, although there is some loss of information, this loss is much smaller thanks to the presence of tapetum lucidumSo that a much larger proportion of light is retained in the retina and the eye sticks can process a lot more information.
Not just cats
Tapetum lucidum is what makes cats’ eyes glow in the dark, but it’s a biological adaptation shared with other species. And cats aren’t the only creatures whose eyes glow at night. The same effect can be seen in most feline species and even in most dogs. Bats, sharks, horses, crocodiles or even cows have tapetum lucidum.
They are generally nocturnal animals, both in terms of predators and prey. And it is that evolution has led to the emergence of such structures so that the beings that live and act mainly at night or the prey or predators carrying these habits can survive. However, most diurnal animals usually do not own it, such as humans and pigs.
Can this cause them difficulty?
Tapetum lucidum has many advantages, but you would think that it can be a disadvantage in situations where there is a lot of light, such as during the day. However, cats’ vision has other characteristics that allow them to adapt to other difficulties.
Among them, they have a pupil capable of contracting to unsuspected limits, contracting into a narrow band, and reducing the amount of light that enters the eyes when intense.
- Coles, JA (1971). Certain reflective properties of the cat’s eye Tapetum lucidum J. Physiol .; 212 (2): 393-409.