See the world through the eyes of animals

Nov 21, 2016 | Science

Vision or visual perception is the ability to see, organize and interpret one’s environment. It is dependent on many factors such as field of view, color differentiation, perception of depth and motion & acuity (or focusing ability). The functioning of these factors varies from one species to another, causing human vision to be quite different from, say, dog vision or cat vision. Dogs are quite near-sighted, twice as worse as humans in differentiating shades and have a vision similar to people with red-green color blindness. But they have an accentuated sense of hearing and smell that helps them ‘see’ the world. Every species in the animal kingdom has evolved vision based on its needs and activities. So, an eagle has a sharper vision to detect its prey from great distances while an owl has better nocturnal vision to see well during night-time, its active period. In this article, we look at how amazingly varied animal vision is and how different animals see objects and things compared to how humans see.

Animal Vision vs Human Vision

Human vs Dog vision

Dog vision is akin to human vision with red-green color blindness; what appears ‘red’ to us appears yellow to dogs and ‘green’ appears white or gray. Effectively, their visual world consists of yellows, blues and grays. The visual world of humans, however, consists of reds, greens and blues and all the other colors we see are a combination of these colors. Dogs have a low visual acuity with half the accuracy of humans in detecting brightness or shades. However, their ability to visually discriminate moving objects is very good and have more rod cells than humans, giving them better night vision. Many long-nosed dog breeds, such as sighthounds, have a wider peripheral vision with a field of vision up to 2700 compared to 1800 for humans.

Dog vision vs Human vision

Human vs Bee vision

Like humans, bees have primarily 3 color receptors. Unlike humans, though, they are green, blue and Ultraviolet. The UV vision of bees enables them to spot patterns on flower petals that guide them to nectar. Studies show that some spiders have also evolved to spin UV patterns into their webs to fool bees and trap them! Humans, though, don’t have the ability to perceive UV as a separate color. In addition to UV vision, bees can also detect polarization of light. Air molecules scatter photons to create a pattern of polarized light, which helps bees to navigate by the position of the sun.

Bee vision vs Human vision

Human vs Shark vision

Structurally, a shark’s eye is similar to human eye. However, when it comes to underwater vision, humans are no match for the sharks, whose underwater vision is estimated to be about 10 times better than ours in clear water. Sharks’ eyes are equipped with tapetum lucidum, a tissue of mirrored crystals behind the retina. This enables light that has escaped detection to be reflected back to the retina a second time, which increases the sensitivity of their eyes and enables them to see better, even in dark or murky waters. Although this process reduces their visual acuity a little, sharks are also blessed with keen electroreception (ability to detect vibrations) and chemoreception (ability to detect chemical changes in water) senses that help them in hunting.

How animals see: Shark vision

Human vs Snake vision

Snakes, unlike what many people believe, do have adequate vision to track movements but it’s generally not sharp. Their vision varies greatly with some just able to distinguish light from dark, while others, such as arboreal snakes, have good eyesight. Snakes generally use their forked tongues to smell and track their prey. Many snakes such as pit vipers, pythons and boas have infrared- sensitive receptors, which sense heat and create a thermal image of their prey, thereby enabling them to “see” the radiated heat. While snakes may not be blessed with great eyesight, they are very sensitive to vibration and can sense animals around them by faint vibrations in the ground.

How snakes see

Human vs Cat vision

Cats have the ability to see some colors but are able to more clearly distinguish colors near the blue end of the spectrum than the red end of the spectrum. Hence, their visual world consists primarily of blues and yellows. Studies suggest their eyes also exhibit sensitivity to ultraviolet light. Cats, like dogs, sharks and many other animals, are also equipped with tapetum lucidum, a reflective layer behind the retina, that improves their ability to see in darkness. In fact, the minimum light detection level for a cat’s eye is 7 times lower than human eye, resulting in better night vision in cats. Since the tapetum lucidum also results in lesser visual acuity, their ability to see well in bright light is hampered. They have a visual field of view of 2000 compared to 1800 in humans, resulting in wider peripheral vision. However, the absence of fovea in cats results in reduced sharpness and lesser eye resolution compared to humans.

Cat Vision vs Human Vision
How cats see at night

PC: Nickolay Lamm