Abstract
In this study, we measured aerial visual acuity in harbor seals. As a first approach to the hypothesis that harbor seals can obtain acute aerial visual acuity mediated by the interaction of the vertical slit-shaped pupil and the corneal flattening although refractive measurements had revealed aerial myopia, visual acuity was tested as a function of luminance and pupil dilation. We analyzed aerial visual acuity (minimal resolvable stripe width) in three harbor seals in a two-alternative-forced-choice discrimination experiment. Our results further support the hypothesis that harbor seals possess an aerial visual acuity comparable to the acuity in clear waters if the vertical slit pupil does not exceed the zone of corneal flattening in bright light. When the pupil dilates with decreasing luminance, visual acuity decreases which might be due to deflected light from the stronger curved peripheral cornea.
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Abbreviations
- IR:
-
Infrared
- SD:
-
Standard deviation
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Acknowledgments
The authors would like to thank Christine Scholtyssek and Wolf Hanke for critically reading the manuscript. This study was supported by a grant of the Studienstiftung des Deutschen Volkes (2005 SA 0969) to FDH and grants of the VolkswagenStiftung and the Deutsche Forschungsgemeinschaft (SFB 509) to GD. The experiments were in line with the current German law on the protection of animals.
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Hanke, F.D., Dehnhardt, G. Aerial visual acuity in harbor seals (Phoca vitulina) as a function of luminance. J Comp Physiol A 195, 643–650 (2009). https://doi.org/10.1007/s00359-009-0439-2
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DOI: https://doi.org/10.1007/s00359-009-0439-2