See Like Animals Open the tool
Menu

Mexican howler monkey vision: the science and the numbers

Alouatta caraya · order Primates · Mammals: all the numbers

Its sharpest vision resolves 59.61 cycles per degree, against 63.75 for people in this dataset.[5] Its activity pattern is diurnal.[11][12][13][14][15]

See it on your photoBack to How does the Mexican howler monkey see?
  • 59.61cycles per degree (sharpness)Measured

The Mexican howler monkey (Alouatta caraya) is a mammal in the order Primates. Its eyes belong to the vision type Day dichromat mammal: two cone types (blue and yellow, so reds and greens merge), moderate sharpness and a horizontal band of sharp vision. 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 Mexican howler monkey sees: colour receptors

Mexican howler monkey colour receptor peaks, 300 to 700 nmMexican howler monkey: 3 receptor peaks at 421.5, 532, 558.4 nm; you: 3 at 421.5, 532, 558.4 nm. ultraviolet300400500600700
Mexican howler monkey: 421.5, 532, 558.4 nmPeople: 421.5, 532, 558.4 nmWavelength in nanometres

What stands out

  • Its sharpest vision resolves 59.61 cycles per degree: the finest stripe pattern it can tell apart from grey.
  • Activity pattern: diurnal.

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 Mexican howler monkey (Alouatta caraya), catalogue-v1
DialValueEvidenceSourcesPeople
ColourColour receptors
3 receptor classes: 421.5 nm (VS/SWS (violet)), 532 nm (MWS (green)), 558.4 nm (LWS (long))
receptor set of nearest measured relative Homo sapiens (same order Primates)
Group default[1][2][3][4]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]
SharpnessAcuity
59.61 cycles per degree
median of 1 anatomical-ganglion rows (method priority rule)
Measured[5]Acuity: 63.75 cycles per degree Measured[6][5]
Field of viewBinocular overlap
137°
median of 6 relatives in order Primates: Otolemur crassicaudatus, Cephalopachus bancanus, Aotus trivirgatus, Saimiri sciureus, Macaca mulatta, Homo sapiens
Group default[7][8]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]
Total field of view
200°
median species-v1 total field of order Primates: Homo sapiens
Group default[9]
Sharp zones (foveas)Number of foveas
1
fovea_present / area_centralis_type (retinal topography; count 1 = fovea present, 0 = none)
Measured[10]Number of foveas: 1 Measured[10]
Fovea type: fovea Measured[10]
Fovea type
fovea		Measured[10]
Night visionActivity pattern
diurnal
mode of 5 rows (of 5 rows): diurnal; photopic
Measured (not re-verified)[11][12][13][14][15]Activity pattern: diurnal Measured (not re-verified)[16][17][11][1][12][13][14][15]
Pupil shape: vertical Group default[18][19]
Reflective layer (tapetum): no Measured[20]
Rods vs cones: cone-dominated Derived[16][17][11][1][12][13][14][15]
Rods vs cones
cone-dominated
nocturnal -> rod-dominated; crepuscular / cathemeral / mixed -> mixed; diurnal -> cone-dominated
Derived[11][12][13][14][15]
Motion (flicker fusion)Flicker fusion frequency
69 Hz
median of 3 relatives in order Primates: Macaca mulatta, Macaca nemestrina, Homo sapiens
Group default[21][22][23]Flicker fusion frequency: 60 Hz Measured[21][22]

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