Countershading camouflage: using light for concealing 3D information O Penacchio1, P G Lovell2, G Ruxton, I Cuthill3, J M Harris1 |
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1School of Psychology and Neuroscience, University of St. Andrews, United Kingdom |
| Animal camouflage can only be understood by considering both the environment in which the animal lives and the predator from which it is trying to hide. Countershading is the phenomenon where animals are darker on the dorsal surface and lighter on the ventral surface. There are at least two accounts of how countershading may work. The background matching (BM) hypothesis suggests the animal should be hidden against its background (e.g. viewed from below, the light sky; from above, the dark ground). In essence, this is a two-dimensional (2D) problem. Second, countershading may deliver obliterative shading (OS), so that 3D ‘shape-from-shading’ cues, from self-shadowing, are minimised. Here, we used computational modelling to test how optimal BM and OS depends on the time of the day, or light intensity. We modelled the interaction of light with 3D shapes and found the optimal countershading for different luminance distributions. Further, we analysed and compared what countershading patterns would result from both specialist (single lighting condition) and compromise optimisation strategies (across a number of lighting conditions). |
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