Animal Coloration

One cannot help but be impressed by the diversity of colors seen in animals. In his Colour of Animals, written in 1890, Edward Poulton, an evolutionary biologist and Oxford professor of zoology, provided the first comprehensive text on animal coloration. As a subtext, the book was intended to actively support Charles Darwin’s theory of natural selection, which was then besieged by many of his contemporaries.

Poulton was not the first to comment on coloration in animals. Robert Hooke, a pioneer microscopist, first described the structure and brilliant colors of a peacock’s feathers in his classic 1665 work Micrographie. In Descent of Man, and Selection in Relation to Sex (1871), Darwin proposed that conspicuous coloration evolved to provide individual animals, in particular, male birds, with a reproductive advantage in attracting females. Moreover, duller colors provided birds and insects with camouflage to conceal themselves from the covetous eyes of predators, a concept elaborated upon by Poulton.

In the Colour of Animals and findings by others, coloration was observed to provide animals with a diverse array of survival benefits. Poulton was first to emphasize that camouflage coloration enabled prey to avoid potential predators but also enabled predators to conceal themselves or to lure unsuspecting prey. He acknowledged the work of Henry Bates (1862) on the use of coloration by butterflies to resemble another species and thereby deceive predators; and by Fritz Müller who, in 1878, introduced the concept that coloration served as a warning signal (aposematism) to an approaching predator that the would-be prey was prepared and capable of defending itself.

Feather from the male Indian peafowl (Pavo cristatus), the national bird of India. Male birds are generally more colorful or ornamented than females, perhaps because it confers a reproductive advantage, while females can more easily conceal themselves from predators while raising their young.

Coloration provides animals other survival benefits: Some use flashes of light, bold patterns, or motion to divert attacks by predators. Coloration can protect others against sunburn, while certain frogs lighten or darken their skin to control their body temperature. Male monkeys use coloration to assess the social status of their peers. Poulton concluded that pigments in animal tissues produced coloration and that the brilliant colors seen in some birds were the result of consuming carotenoidcontaining plants.