4 - The history, theory and evidence for a cryptic function of countershading

Summary

It has been evolved alike in many unrelated groups of animals by the hunter and the hunted; in the sea and on land. It tones the canvas on which are painted the Leopard's spots, the Tiger's stripes, and the patterns of smaller Carnivora such as Serval and Ocelot, Civet, and Genet, Jackal and Hyaena. It is the dress almost universally worn by rodents, including the Vizcacha, Jerboas, Gerbils, Cavies, Agouties, Hares, and many other. It is the essential uniform adopted by Conies, Asses, Antelopes, Deer, and other groups of ungulates. It is repeated extensively among the marsupials, as seen in the coloration of the Tasmanian wolf, Opossums, Wallabies and others. It forms the background to reveal the beautiful subtle picture patterns worn by Wheatears, Warblers, Pipits, Woodcock, Bustards, and innumerable other birds. It provides a basic livery for the great majority of snakes, lizards, and amphibians. Among insects it reaches a fine state of perfection in different caterpillars and grasshoppers.

Hugh Cott (1940)

In 1896 American artist and naturalist Abbott Handerson Thayer published an article in The Auk entitled ‘The law which underlies protective coloration’. In this article he observed that ‘animals are painted by nature darkest on those parts which tend to be most lighted by the sky's light, and vice versa’. As an example, Thayer described the plumage of the ruffed grouse, whose feathers are dark brown on the back and blend gradually into white on the underneath. Such a gradation in shading, Thayer hypothesised, made three-dimensional bodies appear less round and less solid by balancing and neutralising the effects of illumination by the sun. Thayer called this type of patterning obliterative shading, which today we term countershading.