Cats function very well in low-light conditions, so much so that cat owners sometimes believe them to be nocturnal creatures. This is incorrect. Instead, cats are crepuscular creatures, meaning that they are most active during dawn and dusk. As for why cats are crepuscular creatures, well, there are a number of benefits for being so. For instance, a lot of predators are active during either the day or the night, meaning that being active during dawn and dusk reduces the chances of an animal running into them. Something that is very important for cats because they are predators that can be predated upon. Furthermore, it is worth mentioning that this can increase the population of crepuscular creatures, thus creating more feeding opportunities for the predators that are active during dawn and dusk.
Regardless, the crepuscular nature of cats means that they are better at seeing under low-light conditions than humans. They can’t see under total darkness. However, cats can see with just one sixth of the light that humans need to see, which is possible because feline eyes have a number of features to help them out in this regard. For example, their pupils can dilate to full circles, thus enabling them to capture more light than otherwise possible. Likewise, feline eyes have more rods when compared with human eyes, which is important because rods are responsible for sensing light. It is not a coincidence that all of these things are beneficial for a cats engaging in normal cat activities during dawn and dusk.
Having said this, it should be mentioned that a simple comparison of feline eyes with human eyes isn’t possible. Yes, there are areas in which feline eyes are much better than human eyes. Their superior night-vision is an excellent example. Moreover, others include their superior field of vision and their superior ability to pick up on subtle movements, both of which are connected to their increased number of rods. However, there are serious tradeoffs for these disadvantages. For instance, the dilated pupils that enable the capture of more light are also responsible for cats having much blurrier vision than humans. Similarly, human eyes have more rods, with the result that we are better at seeing color as well as seeing far-off things. Cats are still capable of seeing color, but they see a more limited palette that isn’t as rich. As such, just because cats have sight that is very well-suited for normal cat activities, that is no reason for cat owners to be envious of them.
Can Any Animal See in Total Darkness?
Some people might be curious if any animal can see in total darkness. For starters, it is worth mentioning that the concept of total darkness can be rather complicated. Generally speaking, when we think of light, we think of what we call visible light. However, visible light is just a part of the electromagnetic spectrum, which goes from the low-frequency radio waves and microwaves to the high-frequency X-rays and gamma rays. Furthermore, it is important to note that we define visible light based on our own capabilities. As such, just because we can’t see what we call infrared light and ultraviolet light, it doesn’t mean that other animals are bound by the same limitations. For example, there are numerous species of fish, frogs, snakes, and blood-sucking insects that can see in infrared. Similarly, both butterflies and reindeer are capable of seeing ultraviolet light. Amusingly, goldfish has the distinction of being the one known species that can see in both infrared and ultraviolet, though insufficient research means that it is perfectly possible that there are other species that can do the same out there. Regardless, the important point is that what counts as total darkness isn’t necessarily total darkness for some species. To be fair, total darkness in the strictest sense is so impractical that it isn’t worth considering. However, it is definitely possible to come up with a set of conditions that produce what is effectively total darkness for known forms of life. Under those circumstances, nothing can see for the simple reason that sight is reliant upon light.
Interested individuals might have heard accounts of people who can still see even under total darkness. However, this has been proven to be a case of the human brain engaging in some very interesting shenanigans. For those who are curious, a pair of researchers looked into whether people could see their own hands moving while in total darkness. Remarkably, between 50 and 75 percent of the participants showed some ability to see their own movements. Something that was actually confirmed by special cameras that captured their eyes following the movement of their hands in a very smooth fashion, which shouldn’t be possible unless their eyes were indeed tracking something. For comparison, the participants who reported an inability to see their own movements showed no such smoothness in their eyes but rather the random jerks that are normal when human eyes aren’t tracking something. The researchers weren’t 100 percent why this was the case, but they speculated that the brain was essentially filling in the gaps based on previous experience, which is something that brains do in the case of sight on a regular basis. As for why they suspected that this was the case rather than some people possessing the real ability to see in total darkness, well, suffice to say that the participants had very different results when it came to movements that weren’t their own.
Further evidence for the inability of animals to see in total darkness can be seen in the example of species that have become adapted to living in caves on a full-time basis. Essentially, what happens is that they start losing features that are useless in their circumstances while picking up other features that have become more useful. For example, a lot of cave-dwelling species lack pigmentation because there is no need for it. Similarly, a lot of cave-dwelling species are either blind or have very poor vision, which makes sense because they have no need for the very energy-intensive eyes of their predecessors. Meanwhile, it is very common for these animals to pick up heightened senses of touch, smell, and hearing because those remain useful for them even though they are living in total darkness.