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J Comp Physiol A (2013) 199:509519 DOI 10.1007/s00359-012-0762-x
ORIGINAL PAPER
Are harbour seals (Phoca vitulina) able to perceive and use polarised light?
Frederike D. Hanke Lars Miersch
Eric J. Warrant Fedor M. Mitschke
Guido Dehnhardt
Received: 3 August 2012 / Revised: 13 September 2012 / Accepted: 14 September 2012 / Published online: 18 October 2012 Springer-Verlag Berlin Heidelberg 2012
Abstract Harbour seals are active at night and during the day and see well in both air and water. Polarised light, which is a well-known visual cue for orientation, navigation and foraging, is richly available in harbour seal habitats, both above and below the water surface. We hypothesised that an ability to detect and use polarised light could be valuable for seals, and thus tested if they are able to see this property of light. We performed two behavioural experiments, one involving object discrimination and the other involving object detection. These objects were presented to the seals as two-dimensional stimuli on a specially modied liquid crystal display that generated objects whose contrast was purely dened in terms of polarisation(i.e. objects lacked luminance contrast). In both experiments, the seals performance did not deviate signicantly from chance. In contrast, the seals showed a high baseline performance when presented with objects on a non-modied display (whose contrast was purely dened in terms of luminance). We conclude that harbour seals are unable to use polarised light in our experimental context. It remains for future work to elucidate if they are polarisation insensitive per se.
Keywords Harbour seal Phoca vitulina Polarisation
Object detection Liquid crystal display monitor
AbbreviationsES Experimental subject LCD Liquid crystal display PS Polarisation sensitivity PV Polarisation vision
Introduction
Natural environments are characterised by an abundance of linearly polarised light that arises either from the scattering of sunlight or moonlight in the atmosphere or hydrosphere or from the reection of unpolarised light by surfaces or bodies (Wehner 2001; Sabbah et al. 2005). A number of species, terrestrial as well as aquatic (for review see Horvath and Varju 2004; Sabbah et al. 2005), have been shown to detect linearly polarised light. In contrast, only a few species seem to be able to discriminate between two monochromatic lights of the same intensity, but differing only in their angle of polarisation and/or...