Less a function of are afraid than bewilderment, simply put, deer freeze in headlights since they can’t see.

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Deer eyes vs. Human Eyes

The eye of deer and also people re-superstructure a number of features, yet they likewise have a few far-ranging differences.


Unlike human being pupils, which space round and also when dilated execute not span much the the eye, deer pupils space elliptical (like a cat’s) and can dilate to cover the whole width of the orb. This better dilation enables a lot an ext light to reach the retina, improving vision particularly at dawn and also dusk as soon as deer are most active.


The lens that a deer’s eye is bigger than a human’s, and also this allows an ext light to permeate to the retina.

In addition, since people space most energetic during the day, ours lenses space slightly yellow to filter out damaging ultraviolet rays. By contrast, because deer are energetic at night and also have small danger that eye damage from ultraviolet light, your lenses room clear, which allow deer to check out a little of the UV spectrum – at some point giving that even much better night vision.


Essentially a reflector in ~ the ago of the eye (behind the retina), the tapetum lucidum reflects light back again throughout the retina, drastically increasing its irradiate exposure.

Although not found in humans, it is a common bit of eye anatomy in the pet world. This reflective class is discovered in dogs, cats, raccoons, rodents, birds and even fish, and is the cause of eyeshine – or the reflective glowing often seen when a light access time an animal in the dark.


Both deer and also humans have actually two species of photoreceptors ~ above the retina – rods and cones.

The cones room activated through brighter light and are perceptible to color, as well as help with street vision. Civilization have 3 different species of cone cells, each sensitive to a different color light – red, blue and also green. ~ above the various other hand, deer have actually only two species of cone cells, those that deserve to see blue and also yellow.

As a result, deer view red and orange poorly, and also do not view detail and at a distance as plainly as humans.

However, deer have actually a much greater proportion of stick cells. Rods permit both humans and also deer to distinguish in between light and also dark and also to view in dim irradiate (and in ~ night). Because deer have actually many more rods, castle are better able to watch in low light, and also thus have much superior night vision.


Within the rods is a pigment, called rhodopsin, that absorbs light, and in particular favors green-blue and red-purple irradiate (from i beg your pardon its nickname, visual purple, derives). Due to the fact that of rhodopsin’s capacity to bring an ext light right into the rods, and its affinity because that those color that are most current at night, it aids v night vision. And, due to the fact that deer have an ext rods, and therefore an ext rhodopsin, their ability to absorb irradiate at night, and see, is that lot greater.

However, after rhodopsin absorbs light, the pigment division down right into its component components – scotopsin and retinal. Throughout exposure to continuous light, favor daylight, rhodopsin becomes fully decomposed, and also the eye becomes less sensitive to light due to its absence. Return the pigment will certainly regenerate, that deserve to take some time, and the lack of light.

Non-continuous flashes will certainly also breakdown rhodopsin, however not before the speed overloads the system.

Flash Blindness

When one eye that has been in the dark long sufficient to regenerate far-reaching quantities that rhodopsin is suddenly exposed come bright light, a phenomenon that “bleaching,” or oversaturation, occurs, and also on a enormous scale. The an outcome in people is temporary, or flash, blindness.

With deer, remember that their pupils space larger and far more dilated in ~ night 보다 a human eye. Compound this with the greater amount of light that will reach the retina due to their larger lens, and also their higher concentration the rods (and rhodopsin), and multiply that by two thanks to their tapetum, together this creates a perfect storm the oversaturation.

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Add to this the fact that, as much as the allude of blinding light, the deer had actually been enjoying great night vision (thanks also to your UV vision), and also the merged effect of suddenly blindness should be bewildering and also overwhelming – causing the deer to possibly freeze.

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Bonus Deer Facts:

It has been reported that practically 1 million deer-related engine vehicle crashes happen yearly in the U.S. In 2011, this caused approximately 200 human being deaths and 10,000 an individual injuries, and also $1 exchange rate in financial damage.Depending top top the state and weapon offered (bow, crossbow, rifle, etc.), deer season deserve to start as at an early stage as August and also end as late together February, although October and November are maybe the most renowned months. Numerous deer room killed throughout the season, and also in 2008 alone, the U.S.’s 10 million hunters eliminated 6.2 million deer.Expand because that References