How does the northern fur seal see?
The northern fur seal (Callorhinus ursinus) is a mammal in the order Carnivora. Its eyes belong to the vision type Marine mammal cone monochromat.
Measured in this species: sharpness and night vision. Measured colour or sharpness: a measured receptor set or acuity in this species; other dials come from relatives or group defaults. Every value below carries its evidence level and sources; nothing is typed by hand.
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What stands out
- It has one receptor class for colour, so it sees brightness but no hue.
- Its sharpest vision resolves 6.725 cycles per degree: the finest stripe pattern it can tell apart from grey.
- Its eyes cover about 250° around the head, with 88.5° seen by both eyes at once.
- It stops seeing flicker at 76.25 Hz, against 60 Hz for people in this dataset, so fast motion looks about 1.3 times slower to it.[14][15]
- 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.
| Dial | Value | Evidence | Sources |
|---|---|---|---|
| Colour | Colour receptors 1 receptor class: 501.3 nm (MWS (green)) receptor set of nearest measured relative Zalophus californianus (same family Otariidae) | Estimated | [1] |
| Sharpness | Acuity 6.725 cycles per degree median of 2 anatomical-ganglion rows (method priority rule) | Measured | [2][3] |
| Field of view | Binocular overlap 88.5° median of 4 relatives in order Carnivora: Canis lupus, Felis catus, Mustela putorius, Mustela nivalis | Group default | [4][5] |
| Total field of view 250° median species-v1 total field of order Carnivora: Canis familiaris | Group default | [6] | |
| Sharp zones (foveas) | Number of foveas 0 median of 10 relatives in order Carnivora: Canis lupus, Vulpes lagopus, Acinonyx jubatus, Felis catus, Crocuta crocuta, Enhydra lutris | Group default | [7] |
| Fovea type area centralis, horizontal streak | Group default | [7] | |
| Night vision | Activity pattern cathemeral tie ['cathemeral', 'nocturnal'] broken by species-level studies (round-3 tie-break rule 2) (of 5 rows): cathemeral; mesopic; mixed (nocturnal/crepuscular, cathemeral, crepuscular or diurnal/crepuscular)… | Measured (not re-verified) | [8][9][10][11][12] |
| Rods vs cones mixed nocturnal -> rod-dominated; crepuscular / cathemeral / mixed -> mixed; diurnal -> cone-dominated | Derived | [8][9][10][11][12] | |
| Motion (flicker fusion) | Flicker fusion frequency 76.25 Hz median of 4 relatives in order Carnivora: Felis catus, Canis lupus, Pagophilus groenlandicus, Canis familiaris | Group default | [13][14][15][16] |
Related animals
- California sea lion same vision type
- Harbour seal same vision type
- Northern elephant seal same vision type
- Pacific walrus same vision type
- Harp seal same vision type
- Steller's sea lion same vision type
More mammals: all mammals with measured vision data.
Sources
- Murphy MJ, Westerman EL. 2022. Evolutionary history limits species' ability to match colour sensitivity to available habitat light. Proc R Soc B 289:20220612. Electronic supplementary Table S1. doi.org/10.1098/rspb.2022.0612
- de Sousa AA et al. 2022. A natural history of vision loss: insight from evolution for human visual function. Neurosci Biobehav Rev 134:104550 (mmc, acuity compilation). doi.org/10.1016/j.neubiorev.2022.104550
- Kirk & Kay 2004 Table 2 (anatomical acuity). doi.org/10.1007/978-1-4419-8873-7_20
- 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
- species_v1:Miller & Murphy 1995
- 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
- 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?