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Sea otter vision: the science and the numbers

Enhydra lutris · order Carnivora · Mammals: all the numbers

Its sharpest vision resolves 4.2 cycles per degree, against 63.75 for people in this dataset.[6] Its activity pattern is diurnal.[13][14][15][16][17]

See it on your photoBack to How does the sea otter see?
  • 4.2cycles per degree (sharpness)Measured

The sea otter (Enhydra lutris) is a mammal in the order Carnivora. Its eyes belong to the vision type Night-hunting cat: two cone types, a rod-rich retina with a reflective layer for dim light, and a wide zone seen by both eyes. Measured in this species: sharpness, 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 the sea otter sees: colour receptors

Sea otter colour receptor peaks, 300 to 700 nmSea otter: 2 receptor peaks at 430, 558 nm; you: 3 at 421.5, 532, 558.4 nm. ultraviolet300400500600700
Sea otter: 430, 558 nmPeople: 421.5, 532, 558.4 nmWavelength in nanometres

What stands out

  • Its sharpest vision resolves 4.2 cycles per degree: the finest stripe pattern it can tell apart from grey.
  • 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 sea otter (Enhydra lutris), catalogue-v1
DialValueEvidenceSourcesPeople
ColourColour receptors
2 receptor classes: 430 nm (VS/SWS (violet)), 558 nm (LWS (long))
receptor set of nearest measured relative Mustela putorius (same family Mustelidae)
Estimated[1][2]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][3][4][5]
SharpnessAcuity
4.2 cycles per degree
median of 1 anatomical-ganglion rows (method priority rule)
Measured[6]Acuity: 63.75 cycles per degree Measured[7][6]
Field of viewBinocular overlap
74.5°
median of 2 relatives in family Mustelidae: Mustela putorius, Mustela nivalis
Estimated[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
250°
median species-v1 total field of order Carnivora: Canis familiaris
Group default[11]
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
diurnal
mode of 5 rows (of 5 rows): diurnal; diurnal/crepuscular
Measured (not re-verified)[13][14][15][16][17]Activity pattern: diurnal Measured (not re-verified)[18][13][14][1][15][16][19][17]
Pupil shape: vertical Group default[20][21]
Reflective layer (tapetum): no Measured[22]
Rods vs cones: cone-dominated Derived[18][13][14][1][15][16][19][17]
Rods vs cones
cone-dominated
nocturnal -> rod-dominated; crepuscular / cathemeral / mixed -> mixed; diurnal -> cone-dominated
Derived[13][14][15][16][17]
Motion (flicker fusion)Flicker fusion frequency
76.25 Hz
median of 4 relatives in order Carnivora: Felis catus, Canis lupus, Pagophilus groenlandicus, Canis familiaris
Group default[23][24][25][26]Flicker fusion frequency: 60 Hz Measured[24][25]

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

Sources

  1. Longcore 2023
  2. VPOD in-vivo (MSP / single-cell) lambda… 2025
  3. Kirwan
  4. Müller et al. 2009
  5. Thermal Activation and Photoactivation of Visual… 2004
  6. Veilleux et al. 2014
  7. Kirk et al. 2004
  8. Heesy 2004
  9. Heffner et al. 1992
  10. Campbell & Green 1965
  11. Miller & Murphy 1995
  12. Kopania et al. 2025
  13. Borges et al. 2018
  14. Wilman et al. 2014
  15. Maor et al. 2017
  16. Jones et al. 2009
  17. Moura et al. 2024
  18. Anderson et al. 2017
  19. Schmitz et al. 2011
  20. Banks et al. 2015
  21. Cervino et al. 2021
  22. Guareschi et al. 2025
  23. Haarlem et al. 2026
  24. Healy et al. 2013
  25. Inger et al. 2014
  26. 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.