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California sea lion vision: the science and the numbers

Zalophus californianus · order Carnivora · Mammals: all the numbers

The California sea lion has one cone type, so no colour vision in daylight.[1] Its sharpest vision resolves 5.625 cycles per degree, against 63.75 for people in this dataset.[6][7]

See it on your photoBack to How does the California sea lion see?
  • 1colour receptor classMeasured*
  • 5.625cycles per degree (sharpness)Measured

The California sea lion (Zalophus californianus) is a mammal in the order Carnivora. Its eyes belong to the vision type Marine mammal cone monochromat: a single cone type, so no hue at all, in a rod-dominated eye. Measured in this species: colour, sharpness 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 California sea lion sees: colour receptors

California sea lion colour receptor peaks, 300 to 700 nmCalifornia sea lion: 1 receptor peak at 501.3 nm; you: 3 at 421.5, 532, 558.4 nm. ultraviolet300400500600700
California sea lion: 501.3 nmPeople: 421.5, 532, 558.4 nmWavelength in nanometres

What stands out

  • It has one receptor class for colour, so it sees brightness but no hue.
  • Its sharpest vision resolves 5.625 cycles per degree: the finest stripe pattern it can tell apart from grey.
  • 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 California sea lion (Zalophus californianus), catalogue-v1
DialValueEvidenceSourcesPeople
ColourColour receptors
1 receptor class: 501.3 nm (MWS (green))
measured in this species
Measured (not re-verified)[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)[2][3][4][5]
SharpnessAcuity
5.625 cycles per degree
median of 2 behavioural rows (method priority rule)
Measured[6][7]Acuity: 63.75 cycles per degree Measured[7][8]
Field of viewBinocular overlap
88.5°
median of 4 relatives in order Carnivora: Canis lupus, Felis catus, Mustela putorius, Mustela nivalis
Group default[9][10]Binocular overlap: 122.5° Measured[9][10]
Total field of view: 200° Measured (not re-verified)[11]
Blind area behind the head: 160° Derived[11]
Eye placement: frontal Derived[9][10]
Total field of view
250°
median species-v1 total field of order Carnivora: Canis familiaris
Group default[12]
Sharp zones (foveas)Number of foveas
0
median of 10 relatives in order Carnivora: Canis lupus, Vulpes lagopus, Acinonyx jubatus, Felis catus, Crocuta crocuta, Enhydra lutris
Group default[13]Number of foveas: 1 Measured[13]
Fovea type: fovea Measured[13]
Fovea type
area centralis, horizontal streak		Group default[13]
Night visionActivity pattern
cathemeral
mode of 4 rows (of 6 rows): aquatic; cathemeral; diurnal; mixed (nocturnal/crepuscular, cathemeral, crepuscular or diurnal/crepuscular); nocturnal/crepuscular
Measured (not re-verified)[14][15][16][17][18]Activity pattern: diurnal Measured (not re-verified)[19][14][15][2][16][17][20][18]
Pupil shape: vertical Group default[21][22]
Reflective layer (tapetum): no Measured[23]
Rods vs cones: cone-dominated Derived[19][14][15][2][16][17][20][18]
Rods vs cones
mixed
nocturnal -> rod-dominated; crepuscular / cathemeral / mixed -> mixed; diurnal -> cone-dominated
Derived[14][15][16][17][18]
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[24][25][26][27]Flicker fusion frequency: 60 Hz Measured[25][26]

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

Sources

  1. Murphy et al. 2022
  2. Longcore 2023
  3. Kirwan
  4. Müller et al. 2009
  5. Thermal Activation and Photoactivation of Visual… 2004
  6. de Sousa et al. 2022
  7. Kirk et al. 2004
  8. Veilleux et al. 2014
  9. Heesy 2004
  10. Heffner et al. 1992
  11. Campbell & Green 1965
  12. Miller & Murphy 1995
  13. Kopania et al. 2025
  14. Borges et al. 2018
  15. Wilman et al. 2014
  16. Maor et al. 2017
  17. Jones et al. 2009
  18. Moura et al. 2024
  19. Anderson et al. 2017
  20. Schmitz et al. 2011
  21. Banks et al. 2015
  22. Cervino et al. 2021
  23. Guareschi et al. 2025
  24. Haarlem et al. 2026
  25. Healy et al. 2013
  26. Inger et al. 2014
  27. 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.