Pupil Shape Blog Post!

Submitted by jacksonn1 on Sun, 11/27/2022 - 15:18

The pupil is the round opening in the center of the iris that allows light to enter the eye to be processed by the retina. However, the pupil is not always round! A round pupil is found in humans and other animals like dogs, but other animals can have differently shaped pupils serving different purposes. The various shapes found in the animal kingdom include vertical and horizontal slits, crescent and W-shaped, and circular. But why is there such a variety, and what purpose do they all serve?


Evolution has created these different pupil shapes to help animals survive. Prey animals typically have horizontal slit pupils that provide a wider field of vision. This gives them an advantage in seeing nearby predators. Although their visual field is larger though, their vision is not very sharp, only allowing them to vaguely see the surrounding area. This pupil type can be seen on animals like goats and antelopes!

Why Do Animals Have Differently Shaped Pupils in Their Eyes?

Image result for mongoose pupil  The Evolution Of The Rectangular Eye | Science 2.0


Predatory animals, especially smaller ones, tend to have vertical slit pupils. These animals hunt closer to the ground, so these pupils give them a highly focused field of vision to provide accurate depth and distance perception. These animals also usually hunt at night, so having the vertical slit allows them to narrow the slit during the day to prevent damage from bright light during the day and open up to see more at night. Animals like foxes or house cats typically have this pupil shape.

Why Our Pupils Are Round, Cat's Are Slit And Herbivores' Are Rectangular? –  Juan Pascual  Image result for crocodile eyesImage result for gecko pupils


Larger predatory animals, like lions and humans, will have circular pupils. These animals hunt higher off the ground and in packs and are generally more intelligent. This shape allows an even focus across the entire visual field, but it also doesn’t allow good coping with sudden changes in light as it cannot constrict as tightly. 

Pupil - WikipediaAmazon.com: Close Up Gray Wolf Eyes Portrait Photo Wolf Posters for Walls  Posters Wolves Print Posters Art Wolf Wall Decor Nature Posters Wolf  Decorations for Bedroom Cool Wall Decor Art Print Poster


Crescent-shaped pupils are typically found in sea creatures like dolphins. This shape allows for a wide visual field and reduces the effects of light distortion by water. These animals are able to search for both predators and prey with a huge advantage. 



W-shaped pupils are also found in sea creatures, like cuttlefish. These types of pupils likely evolved from horizontally shaped pupils, but they open in darker environments like the deep sea. This shape allows light to enter the eye from many angles and provides great acuity underwater and decreases light distortions, similar to crescent-shaped eyes.

A cuttlefish with W-shaped pupils which may help them discriminate colors.  - Cuttlefish eye - Cephalopod - Wikipedia | Cuttlefish, Cephalopod, Octopus  eyes. Cuttlefish? More like Cuddle-fish, amirite? : r/aww






Submitted by eeggers on Sun, 11/27/2022 - 22:08


Looks great - I like how you go through all the different types and have the images too.