Compared to most animals, a human’s night vision abilities are next to nonexistent. This is largely because homo sapiens as a species lack a layer of tissue in the eye, the tapetum lucidum, found in many species of animals, that serves to reflect incoming light back to the retina and increase the light given to photoreceptors, resulting in superior night vision.
“Eyeshine” is a result of this process, which is why many animals have eyes that appear to glow under the cover of darkness, especially when there is a specific source of light around, like a flashlight.
But while large arrays of animals have a tapetum lucidum, there are some species that stand above others when it comes to night vision. Not only can these animals see in the dark, they can see colour, a phenomenon that is quite rare in the animal kingdom, and can’t quite be explained.
One example is the elephant hawkmoth, the first species of animal discovered to have colour night vision. Through evolution, the hawkmoth gained lenses in their eyes that are quite large, subsequently shortening the total distance between incoming light and their colour receptors. Hawkmoths are then able take in enough light to see ultraviolet, blue, and yellow light even under near complete darkness, allowing them to find flowers during the night like other insects do in the daylight.
An assortment of nocturnal lemurs also have the rare ability of colour night vision, such as the aye-aye lemur which has eyes that can zero in on blue light when there is limited light. Varieties of insectivore bats, along with fruit-eating varieties have been found to have colour night vision, dispelling the long-standing notion that all bats are blind. In both cases, however, the animals have a need for colour night vision, namely to locate food and be more aware of their surroundings in general in the night.
Helmethead geckoes similarly have large lenses allowing them to recognize colour, though the reason is a mystery. Lizards lack rods (the part of the eye used to detect light in darkness) in their eyes, Helmetheads included, but this specific species somehow developed cones that act like rods, which allow them to be more sensitive to light and endow the lizard with colour night vision. Given that Helmethead geckoes are only active during the day, like almost all lizards, the reason for their colour night vision in an evolutionary context is a mystery.
Humans, as we all know, lack strong night vision capabilities, with colour night vision even being nonexistent. Fortunately, the strongest asset man has is ingenuity. So while we have not evolved with colour night vision, we have developed other means to see under the cover of darkness, namely through night vision technologies.
But even mankind’s creations to see in the night lack the ability to differentiate between colours. Perhaps humanity can look to the animal kingdom in order to improve our own technology, which still pales in comparison to what certain species of animals can do naturally.
Featured image courtesy of: gailhampshir