How Good is Deer’s Night Vision?

Deer are crepuscular animals by nature and typically spend most of their time doing their business at dawn or dusk. However, deer can also be seen thriving at night while evading several threats and predators roaming in the dark.

With only a small amount of moonlight lighting their way, these animals seem to have no problem seeing in the dark. Given that, several people wonder just how good is a deer’s night vision?

How Well Can Deer See In the Dark?

How Good is Deer's Night Vision?

Deer can see extremely well in the dark. Some species can see up to 20 times better than humans do at night. This is attributed to the way that deer eyes are placed on their heads as well as the number of photoreceptors present in their eyes.

Light Detection

Despite the darkness that comes with nighttime, deer eyes can still utilize the low amount of light and move about their surroundings with little to no difficulty.

This is because deer eyes are equipped with photoreceptors known as rod cells. These cells are responsible for night vision and have the ability to detect light in dim settings. In turn, this enables the deer to visualize their surroundings.

In addition to that, deer also have other optic enhancements such as the tapetum lucidum that reflects light thus increasing the brightness.

Color Perception

Colors are light rays that are reflected off of objects. These rays are absorbed by the photoreceptors in charge of color perception, the cone cells, and are translated to a corresponding color depending on its wavelength.

Because cone cells require a lot of light to work, their functions are hindered in dark settings. This renders the deer unable to fully see color at night. Instead, they view dull colors or shades of gray.

However, deer are said to have limited color perception in crepuscular settings. This is due to their sensitivity towards short-wavelength lights such as blue light – the most abundant form of light at dusk and dawn.

Scope of Vision

Deer can visually cover more area due to the location of their eyes. This ability can come in handy at night so that they can easily spot nocturnal predators and threats.

A deer’s eyes are found on the sides of their heads and therefore allow them to see a wider scope of it’s surroundings. In addition to that, their eyes are equipped with horizontal slits that allow them to focus on approximately 300 to 310 degrees around them.

However, these animals have been found to have low visual acuity. This means that while they can view a wider range of area, the images formed by their eyes tend to lack detail and appear more blurry.

Depth Perception

Despite their terrific eyesight, much like in daylight, deer still have trouble with depth perception at night.

Humans have greater depth perception because our eyes are located closer to each other. In comparison, deer’s eyes are located farther from each other and therefore only cover the 40 to 60-degree area where both eyes’ fields of vision overlap.

Movement Detection

Because of the deer’s natural inability to clearly focus on a wide scope of vision, these animals rely on terrific motion detection to evade threats and maneuver around their surroundings.

Deer can detect motion up to 100 to 150 yards away. These values can increase depending on the amount of moonlight they get that night.

This is evident in their high temporal resolution which is quantified with a critical flicker fusion (CFF) of 21.26 to 26.77 Hz. This is much higher than humans who have a CFF of only 10 to 15 Hz.

The higher your temporal resolution, the faster you process visual information. Thus, deer not only have the ability to see movement quicker, their minds process it faster allowing for a speedy response.

Why Do Deer See So Well At Night?

How Good is Deer's Night Vision?

The reason why deer see so well at night lies in the various adaptations their eyes have that enable terrific night vision. Specifically, these are the rod cells, pupil slits, and the tapetum lucidum.

  • Rod cells

Deer eyes have two types of photoreceptors – one of which is the rod cell.  These cells are neurons that are aptly named due to their cylindrical appearance and are the main players as to why deer can see so well in the dark.

These rod cells are easily excited by various intensities of light. This enables these cells to absorb even low levels of light and form images in low-light to dark settings such as nighttime. 

Deer have around 20 times more rod cells than humans do and thus have around 20 times better night vision.

However, these rod cells can only detect the size, shape, and distance of items and cannot detect color. As a result, any image seen through these cells comes out in shades of gray.

  • Pupil Slit

Pupil slits are believed to be evolutionary adaptations that enhance animals’ visions since it allows eyes to limit light to a certain field. 

Because deer have horizontal slits, they see things in a wider scope of the area as opposed to humans who have circular pupils. This is also why deer vision can be likened to panoramic vision. 

Their unique slit allows them to keep their eyes level on the ground despite grazing, so they can keep a constant lookout for predators and threats coming their way.

Plus, it can limit any interfering light coming from above or below allowing them to focus on rays of light directly in front of their eyes.

  • Tapetum lucidum

The tapetum lucidum literally means bright tapestry. This is a layer of tissue found in the eyes of several animals that provides light with a second chance at being detected by the photoreceptors. 

At night, crepuscular animals like deer, only have access to low amounts of light. So, to properly utilize this limited light, this tissue reflects all passing light back to the retina. 

The reflected light, in turn, is exposed more to more photoreceptors and thus have a greater chance of being absorbed. As a result, the tapetum also increases the brightness of deer vision by means of the reflected light. 

While this enhances visual sensitivity, images formed by the reflected light do end up slightly more blurry as opposed to light that was directly absorbed.

Fun fact: This tissue is also why deer’s eyes seem to appear bright and shiny when you directly hit them with a source of light.

Conclusion

The threat of darkness holds no bearing for deer due to their extremely efficient night vision. In addition to their already stellar eyesight during the day, they also have specialized cells and adaptations that enable them to see even better at night.

As a result, these animals can go about their business with little to no problem while always on the lookout for potential threats in even the darkest of nights. 

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