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Loggerhead vision: the science and the numbers

Caretta caretta · Reptiles: all the numbers

The loggerhead has four colour channels, including ultraviolet (379, 450, 495 and 545 nm).[1] The loggerhead stops seeing flicker at 40 Hz, against 60 Hz for people.[24]

See it on your photoBack to How does the loggerhead see?
  • 4colour receptor classesMeasured
  • 40hertz flicker fusion (motion)Measured

The loggerhead (Caretta caretta) is a reptile. Its eyes belong to the vision type Diurnal reptile tetrachromat: four cone types including ultraviolet, coloured oil droplets and one or more foveas. Measured in this species: colour, night vision and motion (flicker fusion). 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 loggerhead sees: colour receptors

Loggerhead colour receptor peaks, 300 to 700 nmLoggerhead: 4 receptor peaks at 379, 450, 495, 545 nm; you: 3 at 421.5, 532, 558.4 nm. ultraviolet300400500600700
Loggerhead: 379, 450, 495, 545 nmPeople: 421.5, 532, 558.4 nmWavelength in nanometres

What stands out

  • It has 4 colour receptor classes, including ultraviolet; people have 3.
  • It stops seeing flicker at 40 Hz, against 60 Hz for people in this dataset, so fast motion looks choppier to it.[24][25]
  • 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 loggerhead (Caretta caretta), catalogue-v1
DialValueEvidenceSourcesPeople
ColourColour receptors
4 receptor classes: 379 nm (UVS), 450 nm (SWS (blue)), 495 nm (MWS (green)), 545 nm (LWS (long))
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]
Ultraviolet
yes: at least one receptor peaks in the ultraviolet		Measured
SharpnessNo value in the catalogue.Acuity: 63.75 cycles per degree Measured[5][6]
Field of viewNo value in the catalogue.Binocular overlap: 122.5° Measured[7][8]
Total field of view: 200° Measured (not re-verified)[9]
Blind area behind the head: 160° Derived[9]
Eye placement: frontal Derived[7][8]
Sharp zones (foveas)Number of foveas
2
group default: mode of tier-A values in vision type the "Diurnal reptile tetrachromat" type within phylum Chordata (1 species: Anolis carolinensis)
Group default[10][11]Number of foveas: 1 Measured[12]
Fovea type: fovea Measured[12]
Fovea type
central fovea, temporal		Group default[10][11]
Night visionActivity pattern
cathemeral
mode of 4 rows (of 4 rows): arrhythmic/cathemeral; cathemeral; diurnal
Measured (not re-verified)[13][1][14][15]Activity pattern: diurnal Measured (not re-verified)[13][16][17][1][18][19][20][15]
Pupil shape: vertical Group default[21][22]
Reflective layer (tapetum): no Measured[23]
Rods vs cones: cone-dominated Derived[13][16][17][1][18][19][20][15]
Rods vs cones
mixed
nocturnal -> rod-dominated; crepuscular / cathemeral / mixed -> mixed; diurnal -> cone-dominated
Derived[13][1][14][15]
Motion (flicker fusion)Flicker fusion frequency
40 Hz
median of 1 bright-light rows (behavioural/whole-eye ERG rows; all rows: [40.0])
Measured[24]Flicker fusion frequency: 60 Hz Measured[24][25]

All reptiles side by side: Reptiles: 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. Kirk et al. 2004
  6. Veilleux et al. 2014
  7. Heesy 2004
  8. Heffner et al. 1992
  9. Campbell & Green 1965
  10. Rasys et al. 2024
  11. Fleishman et al. 1988 / Makaretz & Levine 1980
  12. Kopania et al. 2025
  13. Anderson et al. 2017
  14. Oskyrko et al. 2024
  15. Moura et al. 2024
  16. Borges et al. 2018
  17. Wilman et al. 2014
  18. Maor et al. 2017
  19. Jones et al. 2009
  20. Schmitz et al. 2011
  21. Banks et al. 2015
  22. Cervino et al. 2021
  23. Guareschi et al. 2025
  24. Healy et al. 2013
  25. Inger et al. 2014

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.