How they see
How does a squirrel see the world?
The rare daytime rodent, red-blind
The squirrel is that rare rodent that lives by daylight, and its eyes are built to match: cone-rich, wired for a bright, busy world of leaping between branches. It sees blues and yellows clearly but is blind to red, and it gives up night vision almost entirely in exchange for sharp daytime alertness high in the canopy.
See through their eyes
Human ≈ 60 cpd (20/10)
How sharp is a squirrel's vision?
Its eyes resolve about 4 cycles per degree (20/150 (est.)), while a human reaches around 60 cpd (20/10). Its field of view spans about 340°.
How does a squirrel see a human?
Its eyes resolve about 4 cycles per degree against your 60, so a face has to be roughly 15 times closer for it to pick out the detail you do. Your outline and your movement read clearly; your expression does not.
Colour comparison
How each colour shifts when seen through this animal's eyes, using the same colour model as the app. Tones a screen can't emit (such as ultraviolet) are shown as an approximation.
What colours can a squirrel see?
Blue–yellow dichromacy; cannot see red. Good daylight colour for a rodent.
Photoreceptors
Dichromat (2 cone types), cone-rich (diurnal)
Cone peak sensitivities
- S (blue)440 nm
- M (green)543 nm
How does a squirrel see in the dark?
Poor — built for daylight, unlike most rodents.
How does a squirrel's vision compare to a human's?
A squirrel sees around 20/150 to your 20/20 and two colours to your three. At night it fares worse than you, who at least keep some vision, but by day its wide field holds a constant watch for hawks overhead.
What is special about a squirrel's vision?
- Day-active rodent
- Cone-rich retina
- Wide field for predator detection
What the research shows
Squirrel colour vision has been measured in both tree and ground squirrels, and the page's profile draws on each. Blakeslee, Jacobs & Neitz (1988) characterized the spectral mechanisms of the tree squirrel retina, finding a short-wavelength cone near 440–444 nm, a middle-wavelength cone near 543 nm and rods near 502 nm; earlier ground-squirrel work by Jacobs (1978) supports the same two-cone plan. The dichromacy is sharply defined, with a neutral point near 500 nm and no hue discrimination between about 495 and 505 nm, where the two cone signals balance. Jacobs (1993), a review of colour vision across mammals, supplies the context for why this counts as a strong system for a non-primate.
The retina explains the lifestyle. Squirrels are unusually cone-rich for mammals, with a rod-to-cone ratio of about 2:3, and they have no tapetum, which is why their night vision is poor. Acuity is an estimate of around 4 cpd, which is also what the simulation uses; flicker fusion of 80–120 Hz is estimated rather than measured. One modeling limit deserves stating. Because the 543 nm cone sits between the human M and L cones, the choice of a protanopia-based transform is borderline, and any matrix built on human colour-blindness is an analogue of the squirrel's colour space, not a reconstruction of it.
Guides: Are animals colour blind? · Which animal has the best eyesight? · All guides
Scientific sources
- Jacobs (1993)
- Kryger, Amthor & Jacobs (1998)
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