If you think that all creatures on this planet see objects the same way we do, then you are wrong. Living creatures’ visual perception of the surroundings depends on how their eyes process light.
Humans are trichromats; our eyes have three types of photoreceptors known as cone cells, which are sensitive to red, green, and blue. A different type of photoreceptors called rods detect small amounts of light; this allows us to see in the dark. Some animals, on the other hand, have only two types of photoreceptors, which renders them partially colorblind. Others, however, have four types of photoreceptors, which enables them to see ultraviolet light, while some can detect polarized light, meaning light waves that are oscillating in the same plane.
Scientists assert that good color vision helps animals find food on land or in water; for instance, good color vision helps land animals differentiate between ripe red fruit and unripe green fruit. Moreover, colors can make animals more attractive to each other. The ability to see colors also helps animals identify predators or any other thing that might attack them.
So, how do animals see the world?
Cats and Dogs
Cats and dogs are color blind; they only see very pale shades of color. Many of them have vision similar to humans who have red-green color blindness. According to Dan-Eric Nilsson, Professor of Zoology at the University of Lund, Sweden; and coauthor of the Animal Eyes book; cats vision is six times blurrier than ours in daylight, but is better at night, with sensitivity to movements. This is because they have more rods than humans; this ability enables them to hunt at night
Horses
Like zebras, horses eyes are pointing sideways to give them outstanding peripheral vision; this also helps them avoid predators and escape when possible. However, these animals have a blind spot directly in front of their noses, they also lack binocular vision; that is, a horse will always see two images and cannot merge them together like a human. Although horses have better night vision than humans, their color vision is rather poor; they can distinguish green and blue, but a horse’s sight is mostly in shades of grey.
Rattlesnakes
Rattlesnakes have low-resolution color vision during daylight and their vision is very dependent on movement, but very good color vision at night. They pick up infrared heat signals from warm objects around them because they have special sensory tools called pit organs.
Pit organs are a pair of holes on either side of the snout between the eye and the nostril; in each pit, a thin membrane is suspended to detect heat. According to David Julius, Professor of Physiology at the University of California, San Francisco; a neural receptor, is found in the snake’s nerve cells and connected to this membrane; this receptor is responsible for the snake’s ability to transform infrared light into nerve signals.
References
http://nautil.us/
http://www.eyes-and-vision.com/
http://www.iflscience.com/
http://www.colormatters.com/
http://phys.org/
http://io9.com/
http://news.discovery.com/
Cover Image by freepik