Optimizing countershading camouflage

Optimizing countershading camouflage

Countershading, the widespread tendency of animals to be darker on the side that receives strongest illumination, has classically been explained as an adaptation for camouflage: obliterating cues to 3D shape and enhancing background matching. However, there have only been two quantitative tests of w...

Full description

Saved in:
Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS Vol. 113; no. 46; pp. 13093 - 13097
Main Authors: Cuthill, Innes C., Sanghera, N. Simon, Penacchio, Olivier, Lovell, Paul George, Ruxton, Graeme D., Harris, Julie M.
Format: Journal Article
Language:English
Published: United States National Academy of Sciences 15-11-2016
Subjects:
Animals
Biological Mimicry
Biological Sciences
Birds - physiology
Color
Defense mechanisms
Larva
Light
Luminosity
Mathematical models
Photobiology
Pigmentation
Predation
Predatory Behavior
Survival analysis
Three dimensional imaging
Weather
defensive coloration
shape perception
shape-from-shading
camouflage
animal coloration
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Countershading, the widespread tendency of animals to be darker on the side that receives strongest illumination, has classically been explained as an adaptation for camouflage: obliterating cues to 3D shape and enhancing background matching. However, there have only been two quantitative tests of whether the patterns observed in different species match the optimal shading to obliterate 3D cues, and no tests of whether optimal countershading actually improves concealment or survival. We use a mathematical model of the light field to predict the optimal countershading for concealment that is specific to the light environment and then test this prediction with correspondingly patterned model “caterpillars” exposed to avian predation in the field. We show that the optimal countershading is strongly illumination-dependent. A relatively sharp transition in surface patterning from dark to light is only optimal under direct solar illumination; if there is diffuse illumination from cloudy skies or shade, the pattern provides no advantage over homogeneous background-matching coloration. Conversely, a smoother gradation between dark and light is optimal under cloudy skies or shade. The demonstration of these illumination-dependent effects of different countershading patterns on predation risk strongly supports the comparative evidence showing that the type of countershading varies with light environment.
Bibliography:ObjectType-Article-1
SourceType-Scholarly Journals-1
ObjectType-Feature-2
content type line 23
Edited by Raghavendra Gadagkar, Indian Institute of Science, Bangalore, India, and approved September 30, 2016 (received for review July 14, 2016)
Author contributions: I.C.C., O.P., P.G.L., G.D.R., and J.M.H. designed research; I.C.C. and N.S.S. performed research; O.P. and P.G.L. contributed analytic tools; I.C.C. and N.S.S. analyzed data; and I.C.C., N.S.S., O.P., P.G.L., and J.M.H. wrote the paper.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.1611589113