Frogs Are Night Vision Champions
When it comes to night vision, humans are at a significant disadvantage. In the dark, the best we can hope to make out is general shapes and, if we're lucky, bold patterns. The vibrant colors and definitive shapes we can plainly see in the day are practically impossible to see under the cover of night. We simply aren't designed to be visually effective at night or in dark places because of our evolution as a primarily diurnal species. For nocturnal species, the story is quite different; many species can see quite clearly at night, and use the darkness as an advantage to hunt prey or avoid predators. Their eyes have evolved to be particularly effective even in near pitch black darkness. But even nocturnal species have their visual limitations.
Researchers from Lund University in Sweden believe they have identified the most superior night vision in the animal kingdom: frogs and toads. A recent study showed that not only can frogs and toads clearly see at night, but they are capable of seeing in color...even when it is so dark humans can't see ANYTHING at all!
Humans (and most vertebrates) have two types of cells in the retina: cones and rods. Cones are what allow us to see in color, but they require a large amount of light to function and become far less effective as the light fades. In the darkness, rods take over allowing us to still see, although the vision is limited to black and white. Frogs and toads however have rods of two different sensitivities, a trait that is unique to these amphibians, and it has long been suspected that they may be able to see some color in low-light conditions (finally proven in this study).
"It's amazing that these animals can actually see colour in extreme darkness, down to the absolute threshold of the visual system. These results were unexpected" - Professor of Sensory Biology Almut Kelber at the Faculty of Science, Lund University Source
It was during the third of three experiments that it was revealed that frogs were capable of using their rods to distinguish color in complete darkness. The test was designed to mimic a serious and common situation frogs find themselves in: escaping dark dens on the ground. This is a potentially everyday occurrence as frogs have to find their way out of these dark tunnels after night has fallen. With no available light to navigate, the frog must make use of any sensory information that is available; in this instance, color is likely the best bet for determining which direction is the exit.
The other experiments observed the frogs' reliance on color when searching for a mate or finding food. It was revealed that they stopped relying on color information fairly early when looking for a mate; this makes sense because frogs largely rely on the sounds of breeding calls to find and evaluate a possible mate. They do continue to rely on color-based visual information when hunting, allowing them to make out prey in darkness even when it isn't moving.
"We have previously shown moths and geckos are also able to see colour in inferior light conditions compared to humans. However, frogs apparently have a unique ability to see colour in the dark." - Almut Kelber Source
Article Link: https://www.sciencedaily.com/releases/2017/02/170228131001.htm
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Thank you!