Vision is an amazing gift. Have you ever wondered what vision is like in the animal kingdom?
Birds have four types of cone cells in their eyes called photoreceptors, while humans only have three. This enables the avian species to visualize the world from a completely different perspective and much more clearly than we do.
Dogs only have two cones, blue and yellow but not red and green. Their vision can be compared to a human who is color blind. Dogs are virtually color-blind so they rely on their heightened sense of smell for most of their navigation.
Cats, like dogs and many other animals, have a tapetum lucidum, which is a reflective layer behind the retina that sends light that passes through the retina back into the eye. While this improves the ability to see in darkness, it appears to reduce net visual acuity. The tapetum and other mechanisms give the cat a minimum light detection threshold up to seven times lower than that of humans. This helps them to distinguish movement in the dark.
Pit vipers, like rattlesnakes, can literally see the world in two different ways. They can see some color, but also infrared, with extremely sensitive infrared sensors located on their heads. A rattlesnake has one small pit on each side of its head, filled with thousands of receptor cells which are actually microscopic-sized infrared sensors.