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West Indian manatee vision: the science and the numbers

Trichechus manatus · order Sirenia · Mammals: all the numbers

The west Indian manatee has 2 colour receptor classes (411 and 543 nm): mainly blues and yellows; reds and greens look alike.[1][2][3] Its activity pattern is cathemeral.[16][17][18][19][20][21]

See it on your photoBack to How does the west Indian manatee see?
  • 2colour receptor classesMeasured*

The west Indian manatee (Trichechus manatus) is a mammal in the order Sirenia. Its eyes belong to the vision type Small prey mammal (UV): two or three cone types, often including ultraviolet, low sharpness and a near-panoramic field. Measured in this species: colour, 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 west Indian manatee sees: colour receptors

West Indian manatee colour receptor peaks, 300 to 700 nmWest Indian manatee: 2 receptor peaks at 411, 543 nm; you: 3 at 421.5, 532, 558.4 nm. ultraviolet300400500600700
West Indian manatee: 411, 543 nmPeople: 421.5, 532, 558.4 nmWavelength in nanometres

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.
  • 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 west Indian manatee (Trichechus manatus), catalogue-v1
DialValueEvidenceSourcesPeople
ColourColour receptors
2 receptor classes: 411 nm (VS/SWS (violet)), 543 nm (LWS (long))
measured in this species
Measured (not re-verified)[1][2][3]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][4][5][6]
SharpnessAcuity
17.08 cycles per degree
allometry (Mammalia): log10(acuity_cpd) = intercept + slope * log10(eye_axial_length_mm); slope 1.2182, intercept -0.6097, R2 0.45, n 72 (fitted in this script; fitted range [1.9, 48.147] mm); eye_axial_length_mm…
Estimated[7]Acuity: 63.75 cycles per degree Measured[8][9]
Field of viewBinocular overlap
75°
median of 41 relatives in class Mammalia: Octodon degus, Octodon lunatus, Equus caballus, Ovis aries, Bos taurus, Capra hircus
Group default[10][11][12][13]Binocular overlap: 122.5° Measured[10][11]
Total field of view: 200° Measured (not re-verified)[14]
Blind area behind the head: 160° Derived[14]
Eye placement: frontal Derived[10][11]
Sharp zones (foveas)Number of foveas
0
fovea_present / area_centralis_type (retinal topography; count 1 = fovea present, 0 = none)
Measured[15]Number of foveas: 1 Measured[15]
Fovea type: fovea Measured[15]
Fovea type
none		Measured[15]
Night visionActivity pattern
cathemeral
mode of 4 rows (of 6 rows): aquatic; arrhythmic/cathemeral; cathemeral; mixed (nocturnal/crepuscular, cathemeral, crepuscular or diurnal/crepuscular)
Measured (not re-verified)[16][17][18][19][20][21]Activity pattern: diurnal Measured (not re-verified)[16][17][18][2][19][20][22][21]
Pupil shape: vertical Group default[23][24]
Reflective layer (tapetum): no Measured[25]
Rods vs cones: cone-dominated Derived[16][17][18][2][19][20][22][21]
Rods vs cones
mixed
nocturnal -> rod-dominated; crepuscular / cathemeral / mixed -> mixed; diurnal -> cone-dominated
Derived[16][17][18][19][20][21]
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[26][27][28][29]Flicker fusion frequency: 60 Hz Measured[27][28]

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. VPOD in-vivo (MSP / single-cell) lambda… 2025
  4. Kirwan
  5. Müller et al. 2009
  6. Thermal Activation and Photoactivation of Visual… 2004
  7. Vertebrate eye-size compilation in Thomas et… 2020
  8. Kirk et al. 2004
  9. Veilleux et al. 2014
  10. Heesy 2004
  11. Heffner et al. 1992
  12. Vega-Zuniga et al. 2013
  13. Vega-Zuniga et al. 2017
  14. Campbell & Green 1965
  15. Kopania et al. 2025
  16. Anderson et al. 2017
  17. Borges et al. 2018
  18. Wilman et al. 2014
  19. Maor et al. 2017
  20. Jones et al. 2009
  21. Moura et al. 2024
  22. Schmitz et al. 2011
  23. Banks et al. 2015
  24. Cervino et al. 2021
  25. Guareschi et al. 2025
  26. Haarlem et al. 2026
  27. Healy et al. 2013
  28. Inger et al. 2014
  29. 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.