Lion Eyes: Why Don’t They Look Like Cat Eyes?

The cat family (felidae) is a large and diverse family. It includes big cats such as lions and tigers, medium-sized cats such as bobcats and caracals, and small cats such as domestic cats. Size differences aside, big cats like lions are similar to domestic cats in many ways. They all have beards, are carnivores, and they are very territorial. They also have the same body shape. However, although they are closely related, there are distinct differences between them. One of the subtle differences is that a lion’s eyes don’t look like a cat’s.

The pupils of a lion are usually round, while those of a domestic cat are narrow and vertical, resembling a dagger. Domestic cat eyes seem to be standard for small cats, while big cats like lions and tigers tend to have round pupils.

Despite these differences, there are certain similarities between the eyes of the two feline species. For starters, they all have better eyesight than humans, and their eyes also reflect light at night, giving off a terrifying glow. Pups of both species are born blind. Given all these similarities, why do lions and cats have different eye shapes? Read on to find out.

Why a Lion’s Eyes Don’t Look Like a Cat’s Eyes

Unlike cats, which have vertical slits, lions have round pupils. No one knows exactly why this is, but scientists have come up with a convincing theory for the difference in the eyes of the two feline species. Basically, lion’s eyes are not like cat’s eyes because they are bigger. They hunt their prey differently and are more active during the day than at night.

Martin Banks, a professor of optometry at the University of California, Berkeley, has conducted extensive research to answer questions about differences in eye shape in different animals. The research, carried out in collaboration with Durham University in the UK and published in the journal Science Advances, proposes a hypothesis linking eye shape to the ecological niche an animal occupies.

For the study, Banks and his colleagues analyzed 214 land animal species. The scientists linked the animals’ eye shape (round, horizontal and vertical) to their lifestyle, in terms of how they foraged and what time of day they were more active.

According to the study, the main reason lions don’t have the eyes of small cats is because of their location in the ecosystem. Researchers have found that the pupils of tall prey-chasing animals such as lions, tigers and wolves tend to be round.

In contrast, small cats have vertical slit pupils because they are more likely to be ambush predators. Their small size means they cannot aggressively chase prey like the big cats. Instead, they hunt by stealth.

Size, stealth hunting and eye shape

Concentration is very important for stealth hunting animals. Shorter predators like cats and alligators naturally need more focused eyes because they have to get close to their prey to catch it. The scientists found that eyes with slit pupils were the perfect adaptation to make this possible. Slit eyes allow ambush predators to accurately judge distance through two optical processes called stereovision (or depth perception) and blurring.

Stereoscopic vision is an adaptation that allows the brain to perceive information from each eye at a slightly different angle. Meanwhile, blur refers to the difference in clarity of objects at different distances from the eye. These two phenomena make it easier for small cats to accurately estimate the distance between them and their prey.

Big cats do not require these adaptations. They simply force their way through the hunt by chasing their prey from a distance and lunging at them. Of the 65 ambush predators Banksy studied, 44 had vertical pupils, and 36 of them were less than 16.5 inches tall at the shoulder.

However, there are exceptions. Not all dwarf predators have vertically slit pupils. Pallas the cat is a good example. This feral cat is odd because of its round eyes, even though it is about the same size as the average house cat. The reason is still a mystery, and no one can give a conclusive explanation. However, since small cats with round eyes are outliers, the hypothesis linking slit eyes to small body size seems to hold.

Lions are more active during the day

Another hypothesis is that lions have round eyes because they are generally more active during the day than cats. The pupil of the eye is like the aperture of a camera. It regulates how much goes into the eye by dilating (opening) or contracting (closing).

Round pupils like the lion’s have circular muscles to control how much they open and close, while pupils with vertical slits like the cat’s have muscles on the sides. The result is that the cat’s pupils open and close more strongly, allowing for a greater change in size during the night and letting in more light. The researchers believe this ability helps cats see better in dim light.

Since lions can hunt during the day, they really don’t need specialized eye structures to let more light in. Even without slit pupils, lions can still see well at night thanks to other adaptations, such as the layer of reflective cells behind the retina called the tapetum. It acts like a mirror, helping animals see better in the dark.

Other Interesting Facts About Lion Eyes

• Lions can have blue eyes: Lions have beautiful round brown amber eyes. White lions (lions without the usual lion pigment) have characteristic light brown eyes. However, in rare cases, lions have blue eyes instead of their typical characteristic color.
• Lions can’t see certain colors: The retina of a typical lion contains more rods. The ratio of rods to cones in lions is 25:1. Rods are the reason animals see better in low light. Cones, on the other hand, help organisms distinguish colors. Big cats only have cones for blue and yellow light. This means that lions cannot effectively distinguish red light.
• Lions have an extra eyelid: This extra layer, called the nictitating membrane, provides extra protection for the cornea. The cornea is at the front of the eye and directs light to the retina at the back. The nictitating membrane prevents dust from entering the lion’s eyes. In addition, it keeps the eyes moist, which is necessary for optimal vision.
• Lions are born blind: Like kittens, lion cubs are born blind. It takes about four days for them to gradually regain their vision. This makes them very vulnerable and completely dependent on their mother.

in conclusion

We still don’t fully understand the main reason why animals have different eyes. The root cause appears to be more than feeding technique and whether the animal is nocturnal or diurnal. Regardless, there are high hopes that more focused research will give a more plausible and acceptable explanation.

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