How does having a non-circular pupil affect the way an animal sees?
In: Biology
The pupil of an animal is almost always directly related to their place in the food chain and how they hunt/flee.
If you take a domestic cat for example, they tend to sneak up on their dinner then strike! Their long vertical pupils and ability to dialate their eyes help them see in the dark but also helps to better measure distance.
The horizontal pupils on pray animals is very interesting however! When you look at goats or sheep their eyes are on the sides of their heads as they need to be watching around themselves at all times. The position and horizontal views give them a near panoramic view of their surroundings. When a predator is spotted they must be able to clearly see forward those their eyes are positioned to the side of their head. With their unique pupil shape they can focus ahead and get a very good gauge on distance for an effective escape! This would be like turning off a wide angled view on your phone camera to better focus on the closest items to youA (!)
Edit:
I got lots of questions I did not know the answer to and have spent my morning reading to try to find some answers! I will add I am in no way a proffesional, I just have awful eyesight as was always fascinated by this.
Vertical Slit Pupils – This is common on ambush predators and specifically those low to the ground. Think foxes, cats, snakes and crocodiles. The view from a vertical pupil is going to be elongated vertically with less coming in from the horizon, they also have an ability to dialate more then a circular pupil allowing better sight in low light conditions. This is believed to be seen on predators that are low to the ground because they have a naturally shorter line of sight, and it works to increase depth perception for gauging distance better. Ambush preditors depend on catching their prey quickly, as they are not nearly as adept at a chase.
Circular pupils – We have the most experience with this, as it seen on humans, canines and big cats. Predators that are not low to the ground have a naturally further line of sight, taking away the need to have virtical pupils. This allows a mix of the horizontal and vertical view, but does not seem to have any specialized niche beyond the different level of dilation and thus sight in low light across species. As nature says, if it ain’t broke breed it.
Horizontal pupils – This is common in large prey animals, think goats, horses and moose. This is going to elongate the view of the horizon, shortening the vertical view but allowing for more sight around the body. This is also seen on animals whose eyes are placed to the side of their heads, which still allows them accurately see forward facing, which is vital for running away. It is also believed this gives a steady view of the horizon both when the head is low to graze and the when the head is upright. Another fun fact, most all animals for horizontal pupils have special combs in their eyes to limit light coming from above, stopping the sun from blurring their view of the horizon. The best way to sneak up on a goat is indeed a parachute!
W shaped pupils – Cuttlefish have this specifically as a F*** You to all the research done. It is widely believed to be a cosmic prank, specifically designed to give marine biologists headaches. Not a lot of research has been done, but it appears the W shape allows for better sight in the low light conditions of the Cuttlefishes habitat. Simulations of the eyesight within their habitat shows increased depth perception of shadows allowing for better navigation. It is also theorized to aid in their camouflage.
TLDR and overly simplified version:
Vertical Slit – Like a phone screen
Circular pupil – A standard screen TV (as in a square for all you youngins)
Horizontal Pupils – A widescreen TV
W Shaped Pupils – A bad mushroom trip
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