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Big brown bat vision: the science and the numbers

Eptesicus fuscus · order Chiroptera · Mammals: all the numbers

Its sharpest vision resolves 0.5 cycles per degree, against 63.75 for people in this dataset.[6] Its activity pattern is nocturnal.[12][13][14][15][16][17][6]

See it on your photoBack to How does the big brown bat see?
  • 0.5cycles per degree (sharpness)Measured

The big brown bat (Eptesicus fuscus) is a mammal in the order Chiroptera. Its eyes belong to the vision type Nocturnal mammal (primate, bat): rod-dominated eyes with few working cone types and low sharpness. 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 big brown bat sees: colour receptors

Big brown bat colour receptor peaks, 300 to 700 nmBig brown bat: 2 receptor peaks at 358, 565 nm; you: 3 at 421.5, 532, 558.4 nm. ultraviolet300400500600700
Big brown bat: 358, 565 nmPeople: 421.5, 532, 558.4 nmWavelength in nanometres

What stands out

  • Its sharpest vision resolves 0.5 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 big brown bat (Eptesicus fuscus), catalogue-v1
DialValueEvidenceSourcesPeople
ColourColour receptors
2 receptor classes: 358 nm (UVS), 565 nm (LWS (long))
receptor set of nearest measured relative Myotis velifer (same family Vespertilionidae)
Estimated[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]
Ultraviolet
yes: at least one receptor peaks in the ultraviolet		Estimated
SharpnessAcuity
0.5 cycles per degree
median of 1 behavioural rows (method priority rule)
Measured[6]Acuity: 63.75 cycles per degree Measured[7][6]
Field of viewBinocular overlap
108°
median of 1 relatives in order Chiroptera: Pteropus poliocephalus
Group default[8]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]
Eye placement
frontal		Group default[8]
Sharp zones (foveas)Number of foveas
0
fovea_present / area_centralis_type (retinal topography; count 1 = fovea present, 0 = none)
Measured[11]Number of foveas: 1 Measured[11]
Fovea type: fovea Measured[11]
Fovea type
horizontal streak		Measured[11]
Night visionActivity pattern
nocturnal
mode of 7 rows (of 7 rows): nocturnal; scotopic
Measured (not re-verified)[12][13][14][15][16][17][6]Activity pattern: diurnal Measured (not re-verified)[12][13][14][1][15][18][16][17]
Pupil shape: vertical Group default[19][20]
Reflective layer (tapetum): no Measured[21]
Rods vs cones: cone-dominated Derived[12][13][14][1][15][18][16][17]
Pupil shape
horizontal		Group default[20]
Rods vs cones
rod-dominated
nocturnal -> rod-dominated; crepuscular / cathemeral / mixed -> mixed; diurnal -> cone-dominated
Derived[12][13][14][15][16][17][6]
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[22][23][24][25]Flicker fusion frequency: 60 Hz Measured[23][24]

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. Campbell & Green 1965
  11. Kopania et al. 2025
  12. Anderson et al. 2017
  13. Borges et al. 2018
  14. Wilman et al. 2014
  15. Maor et al. 2017
  16. Schmitz et al. 2011
  17. Moura et al. 2024
  18. Jones et al. 2009
  19. Banks et al. 2015
  20. Cervino et al. 2021
  21. Guareschi et al. 2025
  22. Haarlem et al. 2026
  23. Healy et al. 2013
  24. Inger et al. 2014
  25. 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.