Squirrels see the world in roughly the same palette as a person with red-green color blindness. They are dichromats, meaning their retinas contain two types of color-detecting cone cells rather than the three types most humans have. Those two cone classes are sensitive to blue-violet light and green light, which gives squirrels a solid ability to distinguish blues from greens and to perceive yellows, but leaves them largely unable to separate reds and oranges from the greens and browns around them. The details vary across squirrel species in ways that say a lot about how each one lives.
The Two Cone Types Behind Squirrel Color Vision
Color vision depends on having multiple types of cone photoreceptors in the retina, each tuned to a different band of the light spectrum. In ground squirrels, electrophysiological recordings have identified two cone classes with peak sensitivities at roughly 437 nm (blue-violet) and 518 nm (green).1Journal of Comparative Physiology A. Spectral sensitivity of ground squirrel cones measured with ERG flicker photometry Tree squirrels such as the eastern grey squirrel show a similar arrangement, with cone peaks measured at about 444 nm and 543 nm, shifted slightly toward longer wavelengths compared to their ground-dwelling relatives.2PubMed. Spectral mechanisms in the tree squirrel retina In both cases the blue-sensitive cone (often called the S cone) and the green-sensitive cone (the M cone) work together to give the animal dichromatic color vision, confirmed across at least five ground squirrel species with no systematic differences found among them.3PubMed. Spectral sensitivity and colour vision in the ground-dwelling sciurids: results from golden mantled ground squirrels and comparisons for five species
Because there are only two cone types, the brain can compare their signals along a single color axis: roughly, blue versus green-yellow. Humans with normal trichromatic vision have a third cone type (sensitive to red-orange wavelengths) that adds a second comparison axis, letting them discriminate reds from greens. Squirrels lack that third axis entirely. So if you imagine stripping red and orange out of a photograph and replacing them with muddy olive-greens and tans, you are getting close to what a squirrel perceives.
Colors Squirrels Can and Cannot Tell Apart
Behavioral experiments have tested whether squirrels can actually use their two cone types to pick out colors in a practical setting. In one study, golden-mantled ground squirrels were trained to press colored bars in a modified Skinner box. They successfully discriminated blue from green, blue from gray, green from gray, yellow from gray, and red from gray. Follow-up tests ruled out brightness cues, confirming the squirrels were genuinely responding to color.4PDXScholar. Color Perception in Golden Mantled Ground Squirrels The ability to separate red from gray might seem surprising for an animal with no red-sensitive cone, but “red from gray” is a different task than “red from green.” A red stimulus still produces some activation in the green-sensitive cone, and the ratio of that response to the blue cone’s near-silence gives the brain enough information to distinguish it from a neutral gray.
Where dichromats really struggle is discriminating colors that differ only along the red-green axis. A ripe red berry against green leaves would pop out instantly for a human but would blend together more for a squirrel. Similarly, orange and yellow likely look almost identical to them, and many shades of green, brown, and reddish-brown probably collapse into a narrow range of similar-looking hues.
The Neutral Point and What Looks Gray
Every dichromat has a spectral “neutral point,” a specific wavelength of light that appears neither bluish nor greenish but simply gray. For ground squirrels, early behavioral work placed this neutral point near a well-defined wavelength in the blue-green region of the spectrum.5Vision Research. Visual sensitivity and color vision in ground squirrels For grey squirrels, recordings put it at about 500 nm.6PubMed. Spectral mechanisms in the tree squirrel retina Light at or very near 500 nm stimulates both cone types in a ratio the brain interprets as colorless. In practical terms, this means a particular shade of cyan-to-teal looks no different from a matching gray to a squirrel, even though a human would see it as a vivid blue-green. Wavelengths shorter than the neutral point look increasingly blue; wavelengths longer than it look increasingly green-to-yellow.
This neutral point matters ecologically. Many objects in a forest reflect light in the 490–510 nm range: lichen-covered bark, certain mosses, the undersides of some leaves. To a squirrel, these surfaces would all be close to achromatic, blending together with the gray tones of branches and stone. Meanwhile, the sky and blue flowers would stand out vividly, and fresh green foliage would register clearly on the long-wavelength side of the spectrum.
A Retina Built for Daytime Color
Squirrel retinas are unusual among mammals. Most mammals are nocturnal or crepuscular, so their retinas lean heavily on rods (the receptors for dim-light vision) with relatively few cones sprinkled in. Squirrels have gone the other direction. The thirteen-lined ground squirrel retina contains about 7.5 million cones and only 1.27 million rods, giving it a cone-to-rod ratio that resembles the central portion of the human retina rather than a typical rodent eye.7PubMed Central. The topography of rod and cone photoreceptors in the retina of the ground squirrel Among those cones, M cones outnumber S cones by about 14 to 1, which means the retina is dominated by green-sensitive receptors, with a relatively sparse scattering of blue-sensitive ones.
This lopsided cone layout has consequences. The dense carpet of M cones gives ground squirrels sharp spatial vision and good sensitivity across the green-to-yellow part of the spectrum. The sparser S cones are enough to enable color discrimination but are not concentrated in one area the way blue cones cluster in the human fovea. Instead, S cone density stays fairly even across the retina, peaking at the temporal edge of a horizontal band of high cone density called the visual streak.8PubMed Central. The topography of rod and cone photoreceptors in the retina of the ground squirrel That streak runs roughly along the horizon of the squirrel’s visual field, which is exactly what you’d expect for an animal that spends its life scanning flat ground for food and predators.
Neural wiring in the retina reinforces this two-channel color system. Recent work on the thirteen-lined ground squirrel’s outer retinal circuitry shows that S cones and M cones feed into separate signaling channels from the very first stage of processing, with distinct horizontal cell connections modulating sensitivity for each cone network independently.9PubMed Central. S-cone-specific circuitry in the outer plexiform layer of a cone-dominant mammal This dedicated circuitry suggests that color discrimination is a priority for these animals, not just a side effect of having two pigments.
Flying Squirrels See a Very Different World
Not all squirrels share this daytime color-optimized system. Flying squirrels, which are nocturnal, have taken a dramatically different evolutionary path. Their retinas are rod-dominated, and the only cones detected by electrophysiology have a single peak sensitivity around 512 nm, with no short-wavelength cone class found at all.10Current Biology. Shortwave visual sensitivity in tree and flying squirrels reflects changes in lifestyle Without a second cone type, flying squirrels are essentially color-blind in the way people commonly imagine the term: they can see brightness differences but cannot distinguish hues.
Flying squirrels compensate in a different spectral direction. Unlike their day-active relatives, whose lenses are yellow and block ultraviolet light, flying squirrels have clear lenses that transmit significant amounts of UVA radiation.11PubMed Central. The spectral transmission of ocular media suggests ultraviolet sensitivity is widespread among mammals Whether flying squirrels actively use UV vision is still debated, but the hardware is in place. UV sensitivity could help them detect urine trails left by other animals (rodent urine fluoresces under UV) or navigate in the low-light conditions of dusk and dawn when some UV is still present in the sky.
The contrast between tree squirrels and flying squirrels illustrates how tightly color vision tracks an animal’s daily schedule. Tree squirrels active in bright daylight have invested in cones for color and sharpness. Flying squirrels active in near-darkness have invested in rods for sensitivity and have let their color vision dwindle. Molecular work has confirmed this: the short-wavelength opsin gene (SWS1) is intact and produces a functional violet-sensitive pigment in grey tree squirrels, with a measured peak at 440 nm.12Current Biology. Shortwave visual sensitivity in tree and flying squirrels reflects changes in lifestyle In flying squirrels, that gene appears to have degraded along with the cone population it once served.
Why Squirrels Cannot See Ultraviolet
Given that many rodents, birds, and insects can see into the ultraviolet, you might expect day-active squirrels to have UV vision too. They don’t, and the reason is their lenses. Diurnal squirrels across the sciurid family have distinctly yellow lenses that filter out all UV wavelengths before the light ever reaches the retina.13PubMed Central. The spectral transmission of ocular media suggests ultraviolet sensitivity is widespread among mammals Chemical analysis of the thirteen-lined ground squirrel’s lens found that its major UV-absorbing compound, N-acetyl-3-hydroxykynurenine, is present at a concentration of about 8.2 millimolar, roughly 11 times the concentration of the analogous UV-filtering compound found in human lenses.14PubMed Central. UV filters in the lens of the thirteen lined ground squirrel (Spermophilus tridecemlineatus)
That is a heavy-duty UV shield. Squirrels are spending long hours in direct sunlight foraging and watching for predators, so there is strong evolutionary pressure to protect the retina from UV damage. The trade-off is that even if a squirrel’s retinal pigments could theoretically detect UV photons, those photons never arrive. The grey squirrel’s S cone pigment peaks at 440 nm, which is violet rather than ultraviolet. Molecular work showed that shifting a single amino acid in that pigment’s sequence would push the peak 76 nm into the UV range, meaning the ancestral pigment was probably UV-sensitive before the lineage evolved its yellow lens and retuned the pigment to match the light it was actually receiving.15Current Biology. Shortwave visual sensitivity in tree and flying squirrels reflects changes in lifestyle
How Squirrel Vision Compares to Ours
Squirrel eyes are sometimes described as a useful model for the human visual system, and the comparison holds up in specific ways. Both species have cone-dominated central retinas, both have blue-sensitive and green-sensitive cones, and both process daylight color vision through opponent-channel circuitry. The ground squirrel retina in particular has been used as a stand-in for studying the human fovea because its dense cone packing and sparse rod population create a simpler version of the cone-rich center of the human eye.16PubMed Central. The squirrel as a rodent model of the human visual system
The key difference, of course, is the missing third cone. Humans with normal vision have L cones peaking around 560 nm (red-orange), M cones around 530 nm (green), and S cones around 420 nm (blue-violet). Squirrels have the equivalent of the S and M cones but nothing in the long-wavelength range. This makes squirrel color vision most comparable to the roughly 8 percent of men who have red-green color deficiency (deuteranomaly or protanopia), though the exact pigment peaks and overall spectral sensitivity are not identical.
In practice, this means squirrels outperform humans in one narrow respect: their cone-dense retinas and horizontal visual streak give them excellent motion detection and spatial resolution along the horizon, which is critical for spotting approaching predators. But they pay for that with a flatter color palette. A human in a forest sees a rich gradient from warm reds and oranges through greens to cool blues. A squirrel sees that same scene as bands of blue, gray-green, and yellowish-brown, with much of the warm end of the spectrum compressed into a few muddy tones.
Practical Implications for Feeders, Gardens, and Deterrents
If you’re trying to attract squirrels, or more commonly trying to keep them away from bird feeders, understanding their color vision can help set realistic expectations. Squirrels are frequently claimed to be attracted to or repelled by certain colors, but these claims rarely account for what the animals actually perceive. A bright red feeder, for instance, looks vivid to you but would appear as a dull greenish-brown to a squirrel. That doesn’t mean squirrels can’t find it. They rely heavily on spatial vision, brightness contrasts, and smell, not on color, to locate food sources.
Squirrel-proof feeder designs that use color as a deterrent are probably not working for the reason their marketing suggests. If a red or orange feeder seems to deter squirrels, it is more likely the structure, material, or placement doing the work than the color itself. On the other hand, highly reflective or UV-bright coatings on feeders or garden ornaments would be invisible in the UV range to day-active squirrels, whose yellow lenses block those wavelengths entirely.
For gardeners worried about squirrels raiding fruit, the dichromatic limitation cuts both ways. Squirrels probably cannot pick out a red tomato or strawberry from the surrounding green foliage by color alone the way a bird or a human can. But they have excellent noses and good spatial memory, so once they know where the food is, color camouflage is irrelevant. Netting and physical barriers remain far more effective than any color-based strategy.
Why Squirrel Color Vision Is Studied at All
The sustained scientific interest in squirrel eyes goes beyond just understanding squirrels. Because most mammals are nocturnal and rod-dominated, finding a small non-primate mammal with a cone-rich retina and functional color vision is genuinely useful for vision research. Ground squirrels have become a workhorse model for studying cone circuitry, retinal disease, and the neural processing of color signals. Their retinal wiring has fewer cell types to sort through than a primate retina, making it easier to trace how cone signals are combined and compared. The recent finding that S cones and M cones in the ground squirrel have dedicated, independently regulated processing channels from the very first synaptic layer supports ideas about how early color processing might work in more complex eyes, including ours.17PubMed Central. S-cone-specific circuitry in the outer plexiform layer of a cone-dominant mammal
The squirrel visual system also offers a window into evolutionary trade-offs. The lineage split between day-active tree squirrels with full dichromatic color vision and nocturnal flying squirrels with almost none is clean enough to study molecular changes in opsin genes and lens chemistry side by side, within closely related species. That kind of natural experiment is hard to find elsewhere among mammals, and it continues to generate insights into how quickly and cleanly a visual system can be remodeled when an animal’s lifestyle changes.