Whitetail Eye Reflectors Were Blue in Northern States and Golden in Georgia

IReflector Colors

Northern Deer Reflected Shorter Wavelengths Than Deer From Georgia

A 2025 study published in the Journal of Experimental Zoology Part A measured the reflective layer at the back of the eye called the tapetum lucidum in 27 deer culled in five states in spring 2023. The researchers removed the cornea, lens and retina before taking measurements so the study measured removed reflectors and never measured live eyeshine.

Our rule is that anyone running a spotlight count or reading night photos should count and locate deer by eyeshine and keep its color out of judgments about a deer's sex, age or origin. Reflector color ranged widely within most states, and neither hue nor saturation differed significantly by age or sex.

IIState Differences

Missouri Peaked Lowest, Georgia Highest and Texas Varied Most

Reflectance peaks above 400 nm differed by state. Missouri had the lowest mean of 453 nm and Georgia had the highest of 601 nm, and both differed significantly from every other state at p < 0.01. Indiana's 473 nm and Minnesota's 475 nm did not differ significantly from Texas's 509 nm. Texas also showed the widest range of individual peaks, from 446 to 675 nm. Hue and saturation followed the same pattern, with the three northern states differing from Georgia and Texas differing from neither group.

The eyes came from culls conducted from March 1 to April 26 by federal and state agencies acting independently of the project. The Texas deer were captive while the rest were free-ranging. Researchers took both eyes immediately after death and kept them in buffered saline for under 36 hours before measuring the center of each tapetum from about 45 mm away. The authors treated each sound eye as a separate sample and checked the results with a mixed model that treated each deer as a random effect, which supported the same patterns.

IIIAuthors' Ideas

Latitude, Canopy and Dark Skies Remain Untested Explanations

The authors describe the results as largely descriptive and raise environmental explanations as possibilities. Reindeer share that kind of tapetum with deer and are the only mammal known to change its color with the seasons, going from gold-turquoise in summer to deep blue in winter. The authors note that the northern whitetail means sit within the winter reindeer peak of 444 to 486 nm. Georgia's mean sits within the summer reindeer range of 541 to 625 nm, with Texas between the two.

The three northern herds were at or above 40° latitude with low to moderate canopy cover, while Georgia was below 35° with high canopy cover. The authors think a reflector tuned to blue would help where long twilight and snowy ground provide plenty of short blue wavelengths. The authors also suggest that Georgia's turquoise-gold reflectors may fit nighttime forest light, which is richer in middle green wavelengths.

Missouri does not fit the latitude pattern. Missouri had the lowest mean peak despite being the southernmost northern site, and the authors think night sky brightness may explain that difference. Only the Missouri site had artificial sky brightness below 90 microcandelas per square meter, with a reading of about 10. In reindeer, prolonged pupil dilation in dim light may cause the winter blue shift. The authors suggest that deer under brighter skies show less pupil dilation at night, which could hold back the same shift.

The seasonal question remains open. Every sample came from March or April away from the solstices and the authors write that they cannot tell whether the differences reflect lasting population traits, seasonal change or both. The authors suggest that Georgia's summer-like reading could reflect an early seasonal shift. Our sight and sound guide explains the cone and ultraviolet tests behind deer color vision, and our moonlight paper considers whether night light is strong enough to matter to deer eyes.

IVBeam Color

Overlapping Reflector Colors Could Not Reveal Origin, Age or Sex

In a living eye a spotlight passes through the cornea and lens, then crosses the retina on its way to the tapetum and again on its way back. Researchers cut away all three tissues for the study. Our read is that the reflector, those tissues, the lamp and the angle all shape the color a hunter sees in a beam. An earlier anatomy study cited by the authors describes the whitetail tapetum as azure blue in the center and blue-green to yellow at the edges, while the researchers measured only the center of each reflector. We think the same eye may reflect a different color when a deer looks away from the beam.

The spread within herds was broad. Minnesota peaks ranged from 445 to 522 nm and Texas peaks ranged from 446 to 675 nm. Those ranges overlapped with ranges in other states so one deer's eye color will not tell you where it lives. A night photo made with an infrared flash records wavelengths above the measured range's upper end of 700 nm, so it contains none of the reflector color measured in the study. Eyeshine still tells you an animal is present and facing the light, which is why our rule is to use it for counting and locating.

VSpring Samples

Researchers Measured Removed Reflectors From Few Deer in One Spring

Sample sizes were small at 3 to 8 deer per state and 27 overall, and the Texas deer were captive. All eyes came from March and April 2023 culls and each state's deer came from one or two collection dates, so a state label may represent one local herd. Treating both eyes from a deer as separate samples adds measurements without adding deer, though the mixed-model check addressed that issue. The study measured reflectors removed from the body without ever measuring live eyeshine, and it sampled no other season. The study ran no tests of deer vision, behavior, detection of hunters or hunting success. The explanations based on latitude, canopy and light pollution are hypotheses from the authors.