If you’ve ever lived with a cat, you know they can be incredibly active at night, often running up and down hallways, and all over their owners’ beds, without bumping into walls. or the doors.
Given their ability to avoid collisions during these late-night exercise sessions, you might think cats have natural night vision. but they do?
According to Caryn Plummer, a clinical specialist in veterinary ophthalmology at the University of Florida College of Veterinary Medicine, that’s not the right question to ask.
“It’s not about seeing in the dark or not seeing in the dark,” he told wordssidekick.com in an email. “the perception of vision, you could say the ‘quality’, is more of a spectrum than a yes or no”.
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plummer explained that the amount of ambient light present influences what an individual, be it a human or a cat, can see. however, compared to humans, cats are much better at distinguishing objects when there is very little light available, and this is largely due to the evolution of their eyes.
“Cats can see in the dark because the structure of their eyes, and specifically their retinas, allows them to see ‘better’ than humans when light levels are low,” Plummer said. “Cats have a higher percentage and concentration of rod photoreceptors than humans, which means they have better light sensitivity and can see more in low light levels than we do.”
according to the cat protection charity (opens in new tab), this abundance of rods means cats can see “six to eight times better” than humans when it’s dark.
So why did cats evolve to have such exceptional night vision?
“Adaptations for vision are the direct result of a species’ need to interact with its environment,” Plummer said. “Cats are obligate carnivores, which means they must eat meat to stay healthy. They cannot produce certain required proteins and must ingest them from an external source. Many of their potential prey are active at night or in low light. ”
despite being more active than the average human at night, cats are not strictly nocturnal animals. rather, they are considered “crepuscular”, or active during twilight, due to their penchant for hunting at dusk and dawn.
However, while feline eyes are designed for nocturnal walks, there is more to cats’ ability to successfully navigate their environment during periods of near darkness than the makeup of their eyes. according to plummer, cats also rely on their other senses.
“Cats have very acute hearing and smell [the sense of smell], which aids in their ability to navigate,” Plummer said. “interacting with the environment requires the collaboration of all the senses.”
So, cats are much more adept at roaming at night than humans, but when it comes to quality of vision, they certainly don’t beat humans during the day.
“In evolution, there is usually a price to be paid for every advantage,” Ron Ofri, a professor of veterinary ophthalmology at the Hebrew University of Jerusalem Koret School of Veterinary Medicine in Israel, told Live Science. in an email.
for cats, the downside of having excellent night vision is having to make do with relatively poor vision during the day.
“As a result of the adaptations that allow such sensitive night vision, their daytime visual acuity is only about 1/7 of ours,” said ofri. “This surprises people who think cats always have excellent vision: they do, but only at night; they have horrible day vision.”
Related: Did North American cats really disappear for 7 million years?
according to plummer, there are other differences between the eyes of humans and cats. for example, cats do not register color in the same way as humans.
“cats have a lower absolute number and concentration of cone photoreceptors compared to humans, so they don’t perceive color like we do, nor do they have the degree of detail resolution that we do”, said plummer.
the cones in the eye are responsible for determining the color of “day vision”. humans have three types of cones, which allow us to perceive the colors blue, green and red, while cats have only two types of cones, which means that what we see as green and red appears gray to cats. cats were long thought to be color blind, but many scientists no longer believe that to be the case, although the discussion continues. It’s now widely thought that cats can see blues and grays (opens in new tab), and potentially some shades of yellow and green as well, but really no one can say for sure.
“Cats are dichromats, which means they have two types of cone photoreceptors, compared to our three types,” Plummer said. “so they don’t see as many colors or colors as bright as we do. we would perceive their daytime visual resolution as fuzzy and out of focus.”
Originally posted on Live Science.
