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Grey squirrel vision: the science and the numbers

Sciurus carolinensis · order Rodentia · Mammals: all the numbers

The grey squirrel has 2 colour receptor classes (444 and 543 nm): mainly blues and yellows; reds and greens look alike.[1] Its sharpest vision resolves 3.9 cycles per degree, against 63.75 for people in this dataset.[5] Both eyes see the same 60° in front of it.[7]

See it on your photoBack to How does the grey squirrel see?
  • 2colour receptor classesMeasured
  • 3.9cycles per degree (sharpness)Measured
  • 60°seen by both eyesMeasured

The grey squirrel (Sciurus carolinensis) is a mammal in the order Rodentia. Its eyes belong to the vision type Small prey mammal (UV): two or three cone types, often including ultraviolet, low sharpness and a near-panoramic field. Measured in this species: colour, sharpness, field of view and night vision. Measured core: measured values on at least 3 of the 6 dials.

This is a simulation built from published eye measurements, not what the animal experiences.

Method: How we know what animals see (the See Like Animals vision engine) · Sources · Last updated . Every value below carries its evidence level and sources; nothing is typed by hand.

What the grey squirrel sees: colour receptors

Grey squirrel colour receptor peaks, 300 to 700 nmGrey squirrel: 2 receptor peaks at 444, 543 nm; you: 3 at 421.5, 532, 558.4 nm. ultraviolet300400500600700
Grey squirrel: 444, 543 nmPeople: 421.5, 532, 558.4 nmWavelength in nanometres

What stands out

  • It has two colour receptor classes (a dichromat): reds and greens fall on one axis, as in red-green colour blindness in people.
  • Its sharpest vision resolves 3.9 cycles per degree: the finest stripe pattern it can tell apart from grey.
  • Both eyes see the same 60° in front of it (binocular overlap), where depth is judged best.
  • Activity pattern: diurnal.

The six dials

Evidence levels: how the tiers work. "Measured" means a value measured in this species; "Estimated" values come from a close relative or an eye-size formula. The last column gives the values for people from the same catalogue.

Vision values for the grey squirrel (Sciurus carolinensis), catalogue-v1
DialValueEvidenceSourcesPeople
ColourColour receptors
2 receptor classes: 444 nm (SWS (blue)), 543 nm (LWS (long))
measured in this species
Measured[1]Colour receptors: 3 receptor classes: 421.5 nm (VS/SWS (violet)), 532 nm (MWS (green)), 558.4 nm (LWS (long)) Measured (not re-verified)[1][2][3][4]
SharpnessAcuity
3.9 cycles per degree
median of 1 behavioural rows (method priority rule)
Measured[5]Acuity: 63.75 cycles per degree Measured[6][5]
Field of viewBinocular overlap
60°
median of 1 rows (eyes-at-rest rows preferred)
Measured[7]Binocular overlap: 122.5° Measured[7][8]
Total field of view: 200° Measured (not re-verified)[9]
Blind area behind the head: 160° Derived[9]
Eye placement: frontal Derived[7][8]
Sharp zones (foveas)Number of foveas
0
median of 2 relatives in family Sciuridae: Ictidomys tridecemlineatus, Otospermophilus beecheyi
Estimated[10]Number of foveas: 1 Measured[10]
Fovea type: fovea Measured[10]
Fovea type
horizontal streak		Estimated[10]
Night visionActivity pattern
diurnal
mode of 9 rows (of 9 rows): diurnal; photopic
Measured (not re-verified)[11][12][1][13][14][15][16][5]Activity pattern: diurnal Measured (not re-verified)[17][11][12][1][13][14][15][16]
Pupil shape: vertical Group default[18][19]
Reflective layer (tapetum): no Measured[20]
Rods vs cones: cone-dominated Derived[17][11][12][1][13][14][15][16]
Rods vs cones
cone-dominated
nocturnal -> rod-dominated; crepuscular / cathemeral / mixed -> mixed; diurnal -> cone-dominated
Derived[11][12][1][13][14][15][16][5]
Motion (flicker fusion)Flicker fusion frequency
103 Hz
median of 1 relatives in genus Sciurus: Sciurus vulgaris
Estimated[21]Flicker fusion frequency: 60 Hz Measured[22][23]

All mammals side by side: Mammals: every measurement. Method: how we know what animals see.

Sources

  1. Longcore 2023
  2. Kirwan
  3. Müller et al. 2009
  4. Thermal Activation and Photoactivation of Visual… 2004
  5. Veilleux et al. 2014
  6. Kirk et al. 2004
  7. Heesy 2004
  8. Heffner et al. 1992
  9. Campbell & Green 1965
  10. Kopania et al. 2025
  11. Borges et al. 2018
  12. Wilman et al. 2014
  13. Maor et al. 2017
  14. Jones et al. 2009
  15. Schmitz et al. 2011
  16. Moura et al. 2024
  17. Anderson et al. 2017
  18. Banks et al. 2015
  19. Cervino et al. 2021
  20. Guareschi et al. 2025
  21. Haarlem et al. 2026
  22. Healy et al. 2013
  23. Inger et al. 2014

Every value cites its sources (all sources). Values were extracted from these works and converted (units, medians, derived values); changes are ours, and the listed sources do not endorse this site. Data: catalogue-v1, built 2026-09-29. Accuracy notes: how accurate is this? Method: how we know.