How does the horse see?
The horse (Equus caballus) is a mammal in the order Perissodactyla. Its eyes belong to the vision type Grazing ungulate panorama: 2 cones, horizontal visual streak, near-panoramic field with a rear blind spot, narrow binocular zone; reindeer add UV lens transmission.
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. Every value below carries its evidence level and sources; nothing is typed by hand.


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.
- It stops seeing flicker at 60 Hz, against 60 Hz for people in this dataset, so fast motion looks about the same.[20][21]
- 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.
| Dial | Value | Evidence | Sources |
|---|---|---|---|
| Colour | Colour receptors 2 receptor classes: 428 nm (VS/SWS (violet)), 539 nm (MWS (green)) measured in this species | Measured | [1] |
| Sharpness | Acuity 20.2 cycles per degree median of 2 behavioural rows (method priority rule) | Measured | [2][3] |
| Field of view | Binocular overlap 42.5° median of 2 rows (eyes-at-rest rows preferred) | Measured | [4][5] |
| Total field of view 350° species-v1.csv | Measured (not re-verified) | [6] | |
| Blind area behind the head 10° blind area = 360 - total field | Derived | [6] | |
| Eye placement lateral frontal if binocular overlap >= 60 deg, else lateral | Derived | [4][5] | |
| Sharp zones (foveas) | Number of foveas 0 fovea_present / area_centralis_type (retinal topography; count 1 = fovea present, 0 = none) | Measured | [7] |
| Fovea type area centralis, horizontal streak | Measured | [7] | |
| Night vision | Activity 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) | [8][9][10][1][11][12][13][14][15] |
| Pupil shape horizontal | Estimated | [16] | |
| Reflective layer (tapetum) yes | Measured | [17][18] | |
| Rods vs cones mixed nocturnal -> rod-dominated; crepuscular / cathemeral / mixed -> mixed; diurnal -> cone-dominated | Derived | [8][9][10][1][11][12][13][14][15] | |
| 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 | [19][20][21][22] |
Comparisons
Related animals
- Black rhinoceros same vision type
- Southern white rhinoceros same vision type
- Cow same vision type
- Pig same vision type
- Sheep same vision type
- Goat same vision type
More mammals: all mammals with measured vision data.
Sources
- Longcore T. 2023. A compendium of photopigment peak sensitivities and visual spectral response curves of terrestrial wildlife to guide design of outdoor nighttime lighting. Basic Appl Ecol 73:40-50. doi:10.1016/j.baae.2023.09.002. doi.org/10.5281/zenodo.8432720
- Caves EM, Fernandez-Juricic E, Kelley LA (2024) Ecological and morphological correlates of visual acuity in birds. J Exp Biol 227(2): jeb246063. Supplementary Table S1.. doi.org/10.1242/jeb.246063
- Kirk EC, Kay RF 2004. The evolution of high visual acuity in the Anthropoidea. In Anthropoid Origins, Table 1 (behavioural acuity). doi.org/10.1007/978-1-4419-8873-7_20
- Heesy CP 2004. On the relationship between orbit orientation and binocular visual field overlap in mammals. Anat Rec 281A:1104, Table 1. doi.org/10.1002/ar.a.20116
- Heffner RS, Heffner HE 1992. Visual factors in sound localization in mammals. J Comp Neurol 317:219, Table 1 (via Evo-M1 sensory merge). doi.org/10.1002/cne.903170302
- species_v1:Timney & Keil 1992
- Kopania EEK, Clark NL. 2025. Mammalian retinal specializations for high acuity vision evolve in response to both foraging strategies and morphological constraints. Evolution Letters 9: qrae072. Supplementary Tables S1-S2.. doi.org/10.1093/evlett/qrae072
- Anderson SR, Wiens JJ. 2017. Out of the dark: 350 million years of conservatism and evolution in diel activity patterns in vertebrates. Evolution 71:1944-1959. Dryad doi:10.5061/dryad.fg700. doi.org/10.5061/dryad.fg700
- Borges R, Johnson WE, O'Brien SJ, Gomes C, Heesy CP, Antunes A (2018) Adaptive genomic evolution of opsins reveals that early mammals flourished in nocturnal environments. BMC Genomics 19:121
- Wilman et al. 2014 EltonTraits 1.0, MamFuncDat.txt. doi.org/10.6084/m9.figshare.3559887.v1
- Maor R, Dayan T, Ferguson-Gow H, Jones KE. 2017. Temporal niche expansion in mammals from a nocturnal ancestor after dinosaur extinction. Nature Ecology & Evolution 1:1889-1895. Supplementary Table 1. doi.org/10.1038/s41559-017-0366-5
- Jones KE et al. 2009. PanTHERIA: a species-level database of life history, ecology, and geography of extant and recently extinct mammals. Ecology 90:2648. Ecological Archives E090-184. doi.org/10.1890/08-1494.1
- Schmitz L, Motani R. 2011. Science 332:705-708, SOM. doi.org/10.1126/science.1200043
- Moura et al. 2024. A phylogeny-informed characterisation of global tetrapod traits addresses data gaps and biases. PLoS Biol 22:e3002658. TetrapodTraits v3.0.1.. doi.org/10.5281/zenodo.22536349
- Veilleux CC, Kirk EC 2014. Visual acuity in mammals. Brain Behav Evol 83:43, Supplementary Table 1 (cleaned CSV in Evo-M1-Trait-Data). doi.org/10.1159/000357830
- Banks MS, Sprague WW, Schmoll J, Parnell JAQ, Love GD. 2015. Science Advances 1:e1500391. doi.org/10.1126/sciadv.1500391
- Fornazari GA, Montiani-Ferreira F, Filho IR, Somma AT, Moore B. 2016. The eye of the Barbary sheep or aoudad (Ammotragus lervia): reference values for selected ophthalmic diagnostic tests, morphologic and biometric observations. Open veterinary journal 6(2):102-113. doi.org/10.4314/ovj.v6i2.6
- species_v1:Standard textbook knowledge
- Haarlem CS, Hynes C, Jackson AL, Mitchell KJ, O'Connell RG, Healy K. 2026. Pace of ecology drives the tempo of visual perception across the animal kingdom. Nature Ecology & Evolution (doi:10.1038/s41559-026-02994-7). Figshare dataset 10.6084/m9.figshare.30556475. doi.org/10.6084/m9.figshare.30556475
- Healy K, McNally L, Ruxton GD, Cooper N, Jackson AL. 2013. Metabolic rate and body size are linked with perception of temporal information. Animal Behaviour 86:685-696. Table 1. doi.org/10.1016/j.anbehav.2013.06.018
- Inger R, Bennie J, Davies TW, Gaston KJ. 2014. Potential biological and ecological effects of flickering artificial light. PLoS ONE 9(5): e98631. Table 3. doi.org/10.1371/journal.pone.0098631
- Lafitte A, Sordello R, Legrand M, Nicolas V, Obein G, Reyjol Y. 2022. A flashing light may not be that flashy: A systematic review on critical fusion frequencies. PLoS ONE 17(12): e0279718. S10 File (CFF database). doi.org/10.1371/journal.pone.0279718
Every value cites its sources (all sources). Data: catalogue-v1, built 2026-09-29. Accuracy notes: how accurate is this?