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Horse vision: the science and the numbers

Equus caballus · order Perissodactyla · Mammals: all the numbers

Horses have 2 colour receptor classes (428 and 539 nm): mainly blues and yellows; reds and greens look alike.[1] Their sharpest vision resolves 20.2 cycles per degree, against 63.75 for people in this dataset.[5][6] Their eyes cover about 350° with 42.5° seen by both eyes; a reflective layer (tapetum) helps in dim light.[11]

See it on your photoBack to How do horses see?
  • 2colour receptor classesMeasured
  • 20.2cycles per degree (sharpness)Measured
  • 350°field of viewMeasured*

The horse (Equus caballus) is a mammal in the order Perissodactyla. Its eyes belong to the vision type Grazing ungulate panorama: two cone types, a horizontal band of sharp vision and a near-panoramic field with a blind area behind the head. Measured in this species: colour, sharpness, field of view, foveas 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 horses see: colour receptors

Horse colour receptor peaks, 300 to 700 nmHorse: 2 receptor peaks at 428, 539 nm; you: 3 at 421.5, 532, 558.4 nm. ultraviolet300400500600700
Horse: 428, 539 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 20.2 cycles per degree: the finest stripe pattern it can tell apart from grey.
  • Its eyes cover about 350° around the head, with 42.5° seen by both eyes at once.
  • Activity pattern: cathemeral.

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 horse (Equus caballus), catalogue-v1
DialValueEvidenceSourcesPeople
ColourColour receptors
2 receptor classes: 428 nm (VS/SWS (violet)), 539 nm (MWS (green))
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
20.2 cycles per degree
median of 2 behavioural rows (method priority rule)
Measured[5][6]Acuity: 63.75 cycles per degree Measured[6][7]
Field of viewBinocular overlap
42.5°
median of 2 rows (eyes-at-rest rows preferred)
Measured[8][9]Binocular overlap: 122.5° Measured[8][9]
Total field of view: 200° Measured (not re-verified)[10]
Blind area behind the head: 160° Derived[10]
Eye placement: frontal Derived[8][9]
Total field of view
350°
species-v1.csv
Measured (not re-verified)[11]
Blind area behind the head
10°
blind area = 360 - total field
Derived[11]
Eye placement
lateral
frontal if binocular overlap >= 60 deg, else lateral
Derived[8][9]
Sharp zones (foveas)Number of foveas
0
fovea_present / area_centralis_type (retinal topography; count 1 = fovea present, 0 = none)
Measured[12]Number of foveas: 1 Measured[12]
Fovea type: fovea Measured[12]
Fovea type
area centralis, horizontal streak		Measured[12]
Night visionActivity pattern
cathemeral
mode of 8 rows (of 9 rows): arrhythmic/cathemeral; cathemeral; diurnal; mesopic; mixed (nocturnal/crepuscular, cathemeral, crepuscular or diurnal/crepuscular)
Measured (not re-verified)[13][14][15][1][16][17][18][19][7]Activity pattern: diurnal Measured (not re-verified)[13][14][15][1][16][17][18][19]
Pupil shape: vertical Group default[20][21]
Reflective layer (tapetum): no Measured[22]
Rods vs cones: cone-dominated Derived[13][14][15][1][16][17][18][19]
Pupil shape
horizontal		Estimated[20]
Reflective layer (tapetum)
yes		Measured[23][24]
Rods vs cones
mixed
nocturnal -> rod-dominated; crepuscular / cathemeral / mixed -> mixed; diurnal -> cone-dominated
Derived[13][14][15][1][16][17][18][19][7]
Motion (flicker fusion)Flicker fusion frequency
60 Hz
median of 21 relatives in class Mammalia: Rattus norvegicus, Cavia porcellus, Mus musculus, Felis catus, Macaca mulatta, Macaca nemestrina
Group default[25][26][27][28]Flicker fusion frequency: 60 Hz Measured[26][27]

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. Caves et al. 2024
  6. Kirk et al. 2004
  7. Veilleux et al. 2014
  8. Heesy 2004
  9. Heffner et al. 1992
  10. Campbell & Green 1965
  11. Timney & Keil 1992
  12. Kopania et al. 2025
  13. Anderson et al. 2017
  14. Borges et al. 2018
  15. Wilman et al. 2014
  16. Maor et al. 2017
  17. Jones et al. 2009
  18. Schmitz et al. 2011
  19. Moura et al. 2024
  20. Banks et al. 2015
  21. Cervino et al. 2021
  22. Guareschi et al. 2025
  23. Fornazari et al. 2016
  24. Standard textbook knowledge
  25. Haarlem et al. 2026
  26. Healy et al. 2013
  27. Inger et al. 2014
  28. Lafitte et al. 2022

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.