See Like Animals Open the tool
Menu

Harbour seal vision: the science and the numbers

Phoca vitulina · order Carnivora · Mammals: all the numbers

The harbour seal has one cone type, so no colour vision in daylight.[1] Its sharpest vision resolves 3.6 cycles per degree, against 63.75 for people in this dataset.[6]

See it on your photoBack to How does the harbour seal see?
  • 1colour receptor classMeasured*
  • 3.6cycles per degree (sharpness)Measured

The harbour seal (Phoca vitulina) 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 harbour seal sees: colour receptors

Harbour seal colour receptor peaks, 300 to 700 nmHarbour seal: 1 receptor peak at 510.2 nm; you: 3 at 421.5, 532, 558.4 nm. ultraviolet300400500600700
Harbour seal: 510.2 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 3.6 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 harbour seal (Phoca vitulina), catalogue-v1
DialValueEvidenceSourcesPeople
ColourColour receptors
1 receptor class: 510.2 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
3.6 cycles per degree
median of 1 behavioural rows (method priority rule); acuity_cpd: larval/juvenile rows (adult rows used) set aside (labelled alternative: 5.7, 8.7)
Measured[6]Acuity: 63.75 cycles per degree Measured[6][7]
Field of viewBinocular overlap
88.5°
median of 4 relatives in order Carnivora: Canis lupus, Felis catus, Mustela putorius, Mustela nivalis
Group default[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
median of 2 relatives in family Phocidae: Leptonychotes weddellii, Mirounga angustirostris
Estimated[12]Number of foveas: 1 Measured[12]
Fovea type: fovea Measured[12]
Fovea type
area centralis		Estimated[12]
Night visionActivity pattern
cathemeral
tie ['cathemeral', 'diurnal'] broken by the broader category (round-3 tie-break rule 3: cathemeral > crepuscular > nocturnal > diurnal) (of 6 rows): aquatic; arrhythmic/cathemeral; cathemeral; diurnal…
Measured (not re-verified)[13][14][15][16][17][18]Activity pattern: diurnal Measured (not re-verified)[13][14][15][2][16][17][19][18]
Pupil shape: vertical Group default[20][21]
Reflective layer (tapetum): no Measured[22]
Rods vs cones: cone-dominated Derived[13][14][15][2][16][17][19][18]
Rods vs cones
mixed
nocturnal -> rod-dominated; crepuscular / cathemeral / mixed -> mixed; diurnal -> cone-dominated
Derived[13][14][15][16][17][18]
Motion (flicker fusion)Flicker fusion frequency
22.5 Hz
median of 1 relatives in family Phocidae: Pagophilus groenlandicus
Estimated[23]Flicker fusion frequency: 60 Hz Measured[24][23]

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. Kirk et al. 2004
  7. Veilleux et al. 2014
  8. Heesy 2004
  9. Heffner et al. 1992
  10. Campbell & Green 1965
  11. Miller & Murphy 1995
  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. Moura et al. 2024
  19. Schmitz et al. 2011
  20. Banks et al. 2015
  21. Cervino et al. 2021
  22. Guareschi et al. 2025
  23. Inger et al. 2014
  24. Healy et al. 2013

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.