In addition to beetles and bees, a number of other animals are now known to see remarkably well in dark environments: cockroaches, lantern fish, cuttlefish, frogs and nocturnal primates such as owl monkeys. So neuroscientists are turning to the question of how they do it.
The gold for night vision goes to owls. These nocturnal predators have large eyes with five times the rod density of human eyes and a tapetum lucidum on top of that. Finally, their swiveling heads give them 270° visibility. All of this allows them to spot small prey across long distances in very low light.
First of all, it is impossible to see anything at all in total darkness. Total darkness means the absence of light, and our eyes depend on light to see.
Large facial eye rings common to owls also reflect light toward the eyes. Contrary to myth, owls cannot see in pitch-black darkness. However, they are able to see with only one-tenth to one-one hundredth the amount of light that humans need to see clearly.
The truth is that cats cannot see in absolute darkness any more than we can. However, they are much better adapted than humans for seeing in low levels of light. They use three clever evolutionary adaptations to allow them to do this. First, as compared to a human eye, the cat eye can let in several times more light.
Like us, cats can't see in the dark when there is absolutely no light available. However, they do have better vision than we do in low light conditions, such as on a moonlit night.
While they can still get around better than humans in total darkness due to their other senses, they will not be able to see. Although it's rare to have complete darkness, it's helpful to turn on a nightlight so your dog can see better at night.
Mantis shrimps probably have the most sophisticated vision in the animal kingdom. Their compound eyes move independently and they have 12 to 16 visual pigments compared to our three. They are the only animals known to be able to see circular polarised light.
Humans have the opposite, which is why we can't see as well at night but can detect colours better. Cats can't see fine detail or rich colour, but have a superior ability to see in the dark because of the high number of rods in their retina that are sensitive to dim light.
Contrary to the popular belief that all nocturnal animals can see well in the dark, many of them actually have poor eyesight. Animals can see in the dark to a certain degree depending on two aspects: the spectral range of light they can see and the structure of their eyes.
Psychology textbooks state that on a clear, dark night, a candle flame can be spotted from as far away as 48 kilometres.
Results indicate that the period of susceptibility to darkness extends only to about 10 weeks of age, which is substantially shorter than the critical period for the effects of monocular deprivation in the primary visual cortex, which extends beyond six months of age.
Alone in the dark
One impact of being in complete darkness is that it can wreck your sleep cycle. Two of the key mechanisms for sleep cycle regulation, the hormone melatonin and the brain's suprachiasmatic nucleus, both rely on light to function. Daylight reduces our levels of melatonin, helping us feel awake.
Thanks to the larger numbers of rods and the tapetum lucidum, your horse has superior night vision. Galloping at full speed through the woods and pastures is no problem for equines. In fact, they see nearly as well in the dark as they do during the day.
Owls are the only animals that have better night vision than felines. The Great Grey Owl has huge black pupils that allow it to see better than any other night animal. Another fascinating thing about an owl's eyes is the creature can't move them. They can only see directly in front of them at all times.
Hogs DO NOT possess this layer - their eyes do not reflect light and their night vision, comparatively speaking, is poor at best. Hogs are not color blind as some may lead you to believe, they have 2 pigment cones in each eye, this results in poor color perception but NOT color blindness.
Lions have fewer cones so see less colour but have great night vision especially since their eyes also have a membrane that concentrates weak light back to the retina and their pupils are able to enlarge to an extent much bigger than ours.
Tiger eyes have large lenses and pupils that increase the amount of light let into the eye. This characteristic helps the tiger with night vision and when there are low light levels available.
Most dogs have only about 30 to 60 degrees of binocular overlap versus approximately 140 degrees cats and humans. But dogs are champions when it comes to visual field of view. That means when King looks straight ahead he can still see 240 degrees, compared to 200 degrees in cats and 180 degrees in humans.
The mantis shrimp's visual system is unique in the animal kingdom. Mantis shrimps, scientifically known as stomatopods, have compound eyes, a bit like a bee or a fly, made up of 10,000 small photoreceptive units.
If you encounter an aggressive lion, stare him down. But not a leopard; avoid his gaze at all costs.
Licking is a natural and instinctive behaviour to dogs. For them it's a way of grooming, bonding, and expressing themselves. Your dog may lick you to say they love you, to get your attention, to help soothe themselves if they're stressed, to show empathy or because you taste good to them!
But there's no need to leave every single light in your home on just for your dog. In fact, darkness at the right time can be good for dogs. According to the Sleep Foundation, dogs, like humans, have circadian rhythms that are influenced by light. It's easier for them to sleep if it's dark, or at least dim.
Yes, your dog knows how much you love him! Dogs and humans have a very special relationship, where dogs have hijacked the human oxytocin bonding pathway normally reserved for our babies. When you stare at your dog, both your oxytocin levels go up, the same as when you pet them and play with them.