How does the Linnaeus's two toed sloth see?
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).
Measured in this species: sharpness, foveas and night vision. Measured core: measured values on at least 3 of the 6 dials. Every value below carries its evidence level and sources; nothing is typed by hand.
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What stands out
- It has three colour receptor classes, like most people.
- Its sharpest vision resolves 1.54 cycles per degree: the finest stripe pattern it can tell apart from grey.
- Both eyes see the same 75° in front of it (binocular overlap), where depth is judged best.
- It stops seeing flicker at 60 Hz, against 60 Hz for people in this dataset, so fast motion looks about the same.[16][17]
- 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.
| Dial | Value | Evidence | Sources |
|---|---|---|---|
| Colour | Colour 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] |
| Sharpness | Acuity 1.54 cycles per degree median of 1 anatomical-ganglion rows (method priority rule) | Measured | [3] |
| Field of view | Binocular overlap 75° median of 41 relatives in class Mammalia: Octodon degus, Octodon lunatus, Equus caballus, Ovis aries, Bos taurus, Capra hircus | Group default | [4][5][6][7] |
| Sharp zones (foveas) | Number of foveas 0 fovea_present / area_centralis_type (retinal topography; count 1 = fovea present, 0 = none) | Measured | [8] |
| Fovea type anakatabatic area, area centralis | Measured | [8] | |
| Night vision | Activity 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) | [9][10][11][12][13][14] |
| Rods vs cones rod-dominated nocturnal -> rod-dominated; crepuscular / cathemeral / mixed -> mixed; diurnal -> cone-dominated | Derived | [9][10][11][12][13][14] | |
| 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 | [15][16][17][18] |
Related animals
- Brown rat same vision type
- House mouse same vision type
- Mongolian jird same vision type
- Common treeshrew same vision type
- Rabbit same vision type
- Syrian hamster same vision type
More mammals: all mammals with measured vision data.
Sources
- Longcore T. 2023. A compendium of photopigment peak sensitivities and visual spectral response curves of terrestrial wildlife to guide design of outdoor nighttime lighting. Basic Appl Ecol 73:40-50. doi:10.1016/j.baae.2023.09.002. doi.org/10.5281/zenodo.8432720
- VPOD in-vivo (MSP / single-cell) lambda max compendium, file scp_cleaned.csv, VPOD GitHub (Frazer et al. 2025 bioRxiv 10.1101/2025.08.22.671864). github.com/VisualPhysiologyDB/visual-physiology-opsin-db/tree/main/scripts_n_notebooks/vpod_ML_workflows/mine_n_match/data_sources/lmax/vpod
- Veilleux CC, Kirk EC 2014. Visual acuity in mammals. Brain Behav Evol 83:43, Supplementary Table 1 (cleaned CSV in Evo-M1-Trait-Data). doi.org/10.1159/000357830
- Heesy CP 2004. On the relationship between orbit orientation and binocular visual field overlap in mammals. Anat Rec 281A:1104, Table 1. doi.org/10.1002/ar.a.20116
- Heffner RS, Heffner HE 1992. Visual factors in sound localization in mammals. J Comp Neurol 317:219, Table 1 (via Evo-M1 sensory merge). doi.org/10.1002/cne.903170302
- Vega-Zuniga T, Medina FS, Fredes F, et al. 2013. Does nocturnality drive binocular vision? Octodontine rodents as a case study. PLoS ONE 8: e84199.. doi.org/10.1371/journal.pone.0084199
- Vega-Zuniga T, Medina FS, Marín G, Letelier JC, Palacios AG, Němec P, Schleich CE, Mpodozis J. (2017). Selective binocular vision loss in two subterranean caviomorph rodents: Spalacopus cyanus and Ctenomys talarum. Scientific reports
- Kopania EEK, Clark NL. 2025. Mammalian retinal specializations for high acuity vision evolve in response to both foraging strategies and morphological constraints. Evolution Letters 9: qrae072. Supplementary Tables S1-S2.. doi.org/10.1093/evlett/qrae072
- Borges R, Johnson WE, O'Brien SJ, Gomes C, Heesy CP, Antunes A (2018) Adaptive genomic evolution of opsins reveals that early mammals flourished in nocturnal environments. BMC Genomics 19:121
- Wilman et al. 2014 EltonTraits 1.0, MamFuncDat.txt. doi.org/10.6084/m9.figshare.3559887.v1
- Maor R, Dayan T, Ferguson-Gow H, Jones KE. 2017. Temporal niche expansion in mammals from a nocturnal ancestor after dinosaur extinction. Nature Ecology & Evolution 1:1889-1895. Supplementary Table 1. doi.org/10.1038/s41559-017-0366-5
- Jones KE et al. 2009. PanTHERIA: a species-level database of life history, ecology, and geography of extant and recently extinct mammals. Ecology 90:2648. Ecological Archives E090-184. doi.org/10.1890/08-1494.1
- Schmitz L, Motani R. 2011. Science 332:705-708, SOM. doi.org/10.1126/science.1200043
- Moura et al. 2024. A phylogeny-informed characterisation of global tetrapod traits addresses data gaps and biases. PLoS Biol 22:e3002658. TetrapodTraits v3.0.1.. doi.org/10.5281/zenodo.22536349
- Haarlem CS, Hynes C, Jackson AL, Mitchell KJ, O'Connell RG, Healy K. 2026. Pace of ecology drives the tempo of visual perception across the animal kingdom. Nature Ecology & Evolution (doi:10.1038/s41559-026-02994-7). Figshare dataset 10.6084/m9.figshare.30556475. doi.org/10.6084/m9.figshare.30556475
- Healy K, McNally L, Ruxton GD, Cooper N, Jackson AL. 2013. Metabolic rate and body size are linked with perception of temporal information. Animal Behaviour 86:685-696. Table 1. doi.org/10.1016/j.anbehav.2013.06.018
- Inger R, Bennie J, Davies TW, Gaston KJ. 2014. Potential biological and ecological effects of flickering artificial light. PLoS ONE 9(5): e98631. Table 3. doi.org/10.1371/journal.pone.0098631
- Lafitte A, Sordello R, Legrand M, Nicolas V, Obein G, Reyjol Y. 2022. A flashing light may not be that flashy: A systematic review on critical fusion frequencies. PLoS ONE 17(12): e0279718. S10 File (CFF database). doi.org/10.1371/journal.pone.0279718
Every value cites its sources (all sources). Data: catalogue-v1, built 2026-09-29. Accuracy notes: how accurate is this?