Why and How Can Animals See In Dark?
Science & Tech / /
It is sure that we, humans, are the most advanced species in this world, but there are some things in which we find ourselves hopeless and the one of them is seeing in the dark. So most of the time we are interested and ask how some creatures which are not so advanced like people are can see in the dark the same way we see in a bright day?
This is an issue which biologist Anna Stöckl from Lund University in Sweden explains (you can see that in the video below).
Different species have evolved differently and use different methods to see in the dark. But before that, it is useful to know how to actually operate our eyes in low light.
Basically, our eyes catch the light particles called photons that strike the photoreceptors of the retina at the back of the eye. They are converted into electrical signals and sent back to the brain, which interprets and tells us what we see. The more light there is around us, the more photons arriving in the eye and look better.
While our eyes somehow get adjusted when dark or in other words, the pupil spreads in a way that it is be able to enter more light - but not so good at seeing in the dark as many other animals like cats and owls.
For example, owls have very large eyes that allow them to collect more photons – something like a touch up of specialized sticks (photoreceptor cells) in the back of the eye. By making circular movements’ reflector system in their eyes called "tapetum lucidum" it allows them to see the light that comes not once, but twice.
Cats also have a structure "tapetum lucidum" as the owls, that when we see their eyes at night, they have a ghostly glow because light reflects back from the photoreceptors.
In the picture below, you can see how animals see in night and how we see in night, and there is quite a difference.
The frogs, however, use different techniques - their eyes take longer to build up a picture, so that more photons to arrive. That means they get an updated picture every four seconds.
Finally, we have to mention the evening star (moth) that can actually see the flowers in color at night. It does this by grouping information from neighboring photoreceptors, thus losing the sharpness and some details.
For some more details, if you are interested, just click on the video below.