Many animals like cats and dogs have better night vision than humans, but not all animals are equipped to see well in the darkness. If you’re wondering which animals struggle to see at night, read on as we dive into the details.
If you’re short on time, here’s the quick answer: Nocturnal animals like owls and raccoons can see very well in the dark due to special adaptations. However, most birds and fish have limited night vision.
Nocturnal Mammals Have Excellent Night Vision
Nocturnal mammals like owls, bats, raccoons, and cats have specially adapted eyes that allow them to see well in the dark. Two key adaptations give them excellent night vision compared to humans and other daytime animals:
Light-Reflecting Tissue in the Eyes
The eyes of nocturnal animals contain a special light-reflecting surface called the tapetum lucidum. This tissue lies behind the retina and reflects visible light back through the retina, giving the light a second chance to activate the animal’s rod photoreceptor cells.
This allows the eyes to make the most of low light conditions.[1]
More Rod Photoreceptors Than Cones
Human eyes use two kinds of photoreceptor cells to see color and details: cones for daytime vision and rods for night vision. Nocturnal mammals have a far higher ratio of rods to cones compared to humans – their retinas may contain over 95% rods rather than only 5-10% as in humans.[2] This rod-dominated retina sacrifices color vision but is far more sensitive in low light.
Animal | Rods | Cones |
---|---|---|
Human | 92 million | 4.6 million |
Cat | 250 million | 1 million |
As the table shows, cats have nearly three times more rod cells than humans, and far fewer cones. This allows them to see in light levels six times lower than humans can.[3] 😺
Diurnal Animals Struggle in Low Light
Photoreceptors Less Sensitive
Many diurnal animals like humans, dogs, and butterflies have eyes adapted for daytime vision with photoreceptors that are not very sensitive. Their eyes cannot collect enough light particles in dim conditions to form sharp images.
For example, the human eye uses cone cells for color vision in bright light. But these cones don’t work well in the dark, leaving us struggling to see when the sun goes down. Comparatively, the rod cells used for peripheral and night vision are 1000 times more sensitive than cones but there are fewer of them.
Butterflies are active during the day so they primarily use photoreceptors tuned to bright light. Their eyes lack the light-gathering power needed for night flights. According to a 2016 study, butterflies have between 12,000 and 20,000 ommatidia (individual eyes) compared to moths which may have over 25,000 per eye.
Each ommatidium must catch enough photons to trigger a visual response. With fewer individual eyes, butterflies simply cannot catch enough light particles to see well at night.
Eyes Did Not Evolve for Darkness
Daytime creatures did not evolve eyes tailored for night vision. Natural selection favored eyes that function best during the hours the animal is active. Humans became diurnal to take advantage of hunting opportunities and plant foods available in daylight.
Our vision adapted to these daytime activities.
Dogs evolved as hunters, scavengers, and watchdogs for human camps. Their eyesight became specialized for daytime tasks like detecting movement, discerning objects, and judging distance. So dogs do not have the huge, light-drinking eyes of nocturnal predators.
According to the AKC, dogs have more rod cells than humans but fewer than cats and significantly fewer than owls and other night-dwelling animals. So canine night vision is decent but not great.
Birds Have Limited Night Vision
Few Nocturnal Bird Species
Unlike many mammals, only a small percentage of birds are nocturnal. Out of the approximately 10,000 bird species worldwide, only around 100 hunt at night. The vast majority of avian species rely on vision over other senses and are active during daylight hours.
Diurnal activity patterns allow most birds to fully utilize their excellent color vision and visual acuity that is suited for daytime conditions.
Owls make up the majority of nocturnal bird species. Their large, forward-facing eyes optimized for low light help them hunt rodents and other prey in darkness. Other examples include nightjars, some albatrosses, shearwaters, and petrels that forage over oceans at night.
More Cones Than Rods in Eyes
Unlike mammals, a higher ratio of cone to rod photoreceptors in avian retinas contribute to their lower sensitivity in low light conditions. Cones allow birds to have excellent daytime vision, perceiving color and fine details. Rods function better for night vision but compromise visual clarity.
For example, oscine songbirds have up to four times as many cones compared to rods. Raptors like hawks and eagles have among the highest cone proportions of all birds, adapted to spotting distant prey while soaring high in daylight.
Even owls have more cones than rods. This cone-rich configuration limits most avian species’ ability to see well in the dark.
Bird Group | Cone/Rod Ratio |
---|---|
Oscine songbirds | 4:1 |
Raptors (hawks, eagles) | 8:1 |
Owls | 2:1 |
While owls like the barn owl (Tyto alba) and barred owl (Strix varia) have higher rod ratios than other bird groups, allowing greater night vision, their visual acuity still pales compared to most mammals. For example, barn owl peak rod density only reaches about 37% of human foveal cone density.
Furthermore, avian photoreceptors may not gather as much light compared to mammals due to differences in retinal oil droplets.
So while iconic nocturnal hunters like owls have suitable adaptations for low light environments compared to other birds, the majority of avian species simply do not have retinal specializations required for true night vision.
Their vision depends much more on photo receptors geared towards excellent daytime sight.
Most Fish Cannot See Well at Night
Lack Adaptations for Low Light
The majority of fish species have limited visual capabilities in low light conditions, such as at night. This is because their eyes lack adaptations that would allow them to see well in the dark. Here are some key reasons why most fish cannot see well at night:
- Their eyes lack a tapetum lucidum – a reflective layer behind the retina that amplifies dim light in animals like cats.
- They have low densities of rods – the photoreceptor cells responsible for low light vision.
- They lack other anatomical features like a large pupil size that improves light gathering.
Without adaptations such as these, the eyes of most fish are not sensitive enough to capture and process images at night or in turbid waters. Their vision is adapted for well-lit conditions during the day. As soon as darkness falls, most fish struggle to see even objects directly in front of them.
Differences Between Species
However, some fish species do have specializations for maximizing vision in low light. Here are some of the differences:
Fish Type | Night Vision Adaptations |
---|---|
Deep sea fish | Tubular eyes, large pupils, high rod density |
Catfish | Tapetum lucidum, upward facing eyes to detect silhouettes |
Sharks | A reflective layer in the retina, a high density of rods |
So while the majority cannot see well in the dark, some species have excellent nighttime vision. But most fish eyes are simply not adapted to function optimally under low light conditions. Their vision depends on daylight conditions, when their eyes can capture enough light to form sharp images.
Conclusion
While many nocturnal mammals like raccoons and cats have specially adapted eyes to see in the dark, most birds, fish, and diurnal animals lack these adaptations. As a result, they struggle to navigate and find food effectively at night compared to animals that are active in the darkness.