CONCEALING COLORATION IN ANIMALS

How differences in coloration within a species reveal new dimensions in the operation of natural selection.

“Studying animal coloration is an exercise in time travel, illuminating the conditions of the past that have produced the diversity of the present,” write Diamond (Curator/Univ. of Nebraska State Museum; World of Viruses, 2012, etc.) and Bond (Center for Avian Cognition/Univ. of Nebraska), who follow their earlier collaboration (Kea, Bird of Paradox: The Evolution and Behavior of a New Zealand Parrot, 1999) with this exploration of how the coloration on bird feathers, fish scales and fur are a response to a complex array of factors. Primary among these is the extent to which coloration allows prey to deceptively merge into the background, providing an edge against predators in the struggle for survival. Equally important is patterning, “the arrangement of splotches, speckles, stripes, and shading that make up an animal's visual appearance.” In a fascinating sidelight, the authors examine how Abbott Henderson Thayer, a prominent American landscape painter, applied his observations about animals to the problem of military camouflage during World War I. Diamond and Bond cover modern research on the change in the numbers of light and dark moths in response to the amount of air pollution and explain how fish have evolved darks scales on top and light underbellies to create the appearance of a flattened object. The deceptive practices of prey also affect the cognitive evolution of predator species, which learn to closely observe their targets, detecting small motions and searching for giveaway signs in order to detect them. This in turn provides an evolutionary advantage to prey that can learn to hide distinguishing features and maintain a still posture. Combining a naturalist’s eye with scientific rigor, the authors report on modern experiments on the mechanisms of the selective process that support these observations.

An intriguing study encompassing “a convergence of disciplines ranging from population ecology and animal behavior to genetics, molecular biology and biophysics.”