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Linnaeus's two toed sloth vision: the science and the numbers

Choloepus didactylus · order Pilosa · Mammals: all the numbers

Its sharpest vision resolves 1.54 cycles per degree, against 63.75 for people in this dataset.[6] Its activity pattern is nocturnal.[14][15][16][17][18][19]

See it on your photoBack to How does the Linnaeus's two toed sloth see?
  • 1.54cycles per degree (sharpness)Measured

The Linnaeus's two toed sloth (Choloepus didactylus) is a mammal in the order Pilosa. 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: 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 Linnaeus's two toed sloth sees: colour receptors

Linnaeus's two toed sloth colour receptor peaks, 300 to 700 nmLinnaeus's two toed sloth: 3 receptor peaks at 424, 502, 538 nm; you: 3 at 421.5, 532, 558.4 nm. ultraviolet300400500600700
Linnaeus's two toed sloth: 424, 502, 538 nmPeople: 421.5, 532, 558.4 nmWavelength in nanometres

What stands out

  • Its sharpest vision resolves 1.54 cycles per degree: the finest stripe pattern it can tell apart from grey.
  • Activity pattern: nocturnal.

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 Linnaeus's two toed sloth (Choloepus didactylus), catalogue-v1
DialValueEvidenceSourcesPeople
ColourColour receptors
3 receptor classes: 424 nm (VS/SWS (violet)), 502 nm (MWS (green)), 538 nm (MWS (green))
receptor set of nearest measured relative Setonix brachyurus (same class Mammalia)
Group default[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
1.54 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
75°
median of 41 relatives in class Mammalia: Octodon degus, Octodon lunatus, Equus caballus, Ovis aries, Bos taurus, Capra hircus
Group default[8][9][10][11]Binocular overlap: 122.5° Measured[8][9]
Total field of view: 200° Measured (not re-verified)[12]
Blind area behind the head: 160° Derived[12]
Eye placement: frontal Derived[8][9]
Sharp zones (foveas)Number of foveas
0
fovea_present / area_centralis_type (retinal topography; count 1 = fovea present, 0 = none)
Measured[13]Number of foveas: 1 Measured[13]
Fovea type: fovea Measured[13]
Fovea type
anakatabatic area, area centralis		Measured[13]
Night visionActivity pattern
nocturnal
mode of 6 rows (of 7 rows): cathemeral; mixed (nocturnal/crepuscular, cathemeral, crepuscular or diurnal/crepuscular); nocturnal; nocturnal/crepuscular; scotopic
Measured (not re-verified)[14][15][16][17][18][19]Activity pattern: diurnal Measured (not re-verified)[20][14][15][1][16][17][18][19]
Pupil shape: vertical Group default[21][22]
Reflective layer (tapetum): no Measured[23]
Rods vs cones: cone-dominated Derived[20][14][15][1][16][17][18][19]
Rods vs cones
rod-dominated
nocturnal -> rod-dominated; crepuscular / cathemeral / mixed -> mixed; diurnal -> cone-dominated
Derived[14][15][16][17][18][19]
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[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. 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. Vega-Zuniga et al. 2013
  11. Vega-Zuniga et al. 2017
  12. Campbell & Green 1965
  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. Schmitz et al. 2011
  19. Moura et al. 2024
  20. Anderson et al. 2017
  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.