How does the harbour seal see?
The harbour seal (Phoca vitulina) is a mammal in the order Carnivora. Its eyes belong to the vision type Marine mammal cone monochromat.
Measured in this species: colour, sharpness 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 one receptor class for colour, so it sees brightness but no hue.
- Its sharpest vision resolves 3.6 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 22.5 Hz, against 60 Hz for people in this dataset, so fast motion looks choppier to it.[14][13]
- 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: 510.2 nm (MWS (green)) measured in this species | Measured (not re-verified) | [1] |
| Sharpness | Acuity 3.6 cycles per degree median of 1 behavioural rows (method priority rule); acuity_cpd: larval/juvenile rows (adult rows used) set aside (labelled alternative: 5.7, 8.7) | Measured | [2] |
| Field of view | Binocular overlap 88.5° median of 4 relatives in order Carnivora: Canis lupus, Felis catus, Mustela putorius, Mustela nivalis | Group default | [3][4] |
| Total field of view 250° median species-v1 total field of order Carnivora: Canis familiaris | Group default | [5] | |
| Sharp zones (foveas) | Number of foveas 0 median of 2 relatives in family Phocidae: Leptonychotes weddellii, Mirounga angustirostris | Estimated | [6] |
| Fovea type area centralis | Estimated | [6] | |
| Night vision | Activity pattern cathemeral tie ['cathemeral', 'diurnal'] broken by the broader category (round-3 tie-break rule 3: cathemeral > crepuscular > nocturnal > diurnal) (of 6 rows): aquatic; arrhythmic/cathemeral; cathemeral; diurnal… | Measured (not re-verified) | [7][8][9][10][11][12] |
| Rods vs cones mixed nocturnal -> rod-dominated; crepuscular / cathemeral / mixed -> mixed; diurnal -> cone-dominated | Derived | [7][8][9][10][11][12] | |
| Motion (flicker fusion) | Flicker fusion frequency 22.5 Hz median of 1 relatives in family Phocidae: Pagophilus groenlandicus | Estimated | [13] |
Comparisons
Related animals
- California sea lion same vision type
- Northern elephant seal same vision type
- Pacific walrus same vision type
- Harp seal same vision type
- Northern fur 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
- Kirk EC, Kay RF 2004. The evolution of high visual acuity in the Anthropoidea. In Anthropoid Origins, Table 1 (behavioural 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
- Anderson SR, Wiens JJ. 2017. Out of the dark: 350 million years of conservatism and evolution in diel activity patterns in vertebrates. Evolution 71:1944-1959. Dryad doi:10.5061/dryad.fg700. doi.org/10.5061/dryad.fg700
- 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
- 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
- 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
- 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
Every value cites its sources (all sources). Data: catalogue-v1, built 2026-09-29. Accuracy notes: how accurate is this?