Rabbits: The Animal Answer Guide

3 Rabbit Colors

Why are so many rabbits brown? The overall coloration of many rabbits and hares appears brownish or grayish, although pikas tend to be reddish to buff colored. But there is a lot of variation in color and color patterns both between and within species, and individual coloration is not uniform over the entire body. The ventral surface of the body (the belly side) is usually lighter than the dorsal surface (the back side). The most typical mammalian color pattern, characteristic not only of lagomorphs but of most rodents, carnivores, and other mammals is called “agouti,” a hue that actually emerges from subtle mixtures of color on individual hairs. An agouti hair is black at the base, yellow in the middle, and black again at the tip, leaving the overall impression of brown to reddish to gray color, depending on the relative amount of two pigments: pheomelanin , which produces red and yellow colors, and eumelanin, which produces dark colors. Lagomorphs have three types of hairs, and while they all are agouti, they express the pattern differently. In the European rabbit, long guard hairs are black but less dark at the base than at the tips. The hairs of most of the fur are black at the tips, yellow in the middle, and bluish at the base. The short hairs of the underfur (pile) are bluish at the base and tipped in yellow. Coat coloration generally has at least three functions in animals: concealment from predators (or, conversely, among predators, concealment from prey), communication, and thermoregulation. There are four general ways in which fur coloration is believed to contribute to concealment. One Chapter 3 Rabbit Colors 49 50 Rabbits: The Animal Answer Guide is background matching, in which an animal’s coloration resembles that of its environment. Agouti coloration is so common because it appears to provide good, all-purpose camouflage in a variety of habitats, making it hard for a predator to detect prey, especially when the prey is not moving. Background matching among lagomorphs is revealed in several general trends. They tend to be paler in desert environments where the vegetation and substrate are pale, darker in forests and woodlands, and more gray and reddish in rocky habitats. The rock rabbits of Africa, for example, all have a reddish tone in their fur. The dark brown fur of the volcano rabbit may match the dark soils and basaltic rock of its volcanic habitat. Black jackrabbits may be the exception that proves the rule. Found only on Espiritu Santo Island in the Gulf of California in Mexico, the black jackrabbit is mostly glossy black and stands out starkly on both green vegetation and bare brown slopes and was described by Howard H. Thomas and Troy L. Bestas as resembling “a short, charred stump.” Because this island has no predatory mammals, selection for concealment may have been No lagomorphs are just plain brown. What appears to be a shadow on the back of the neck gives the Indian hare its other common name: the black-naped hare. Photo © Gehan de Silva Wijeyeratne 51 Rabbit Colors relaxed, allowing a mutation for melanism, or dark coloring, to persist. Similarly, island forms of the Japanese hare (Lepus brachyurus) have darker dorsal pelage (fur) than the mainland ones, and the Amami rabbit is dark, too; in both cases, predatory mammals are absent. The black jackrabbit does have a few avian predators including, notably , great horned owls (Bubo virginianus), one of the few birds of prey able to take adult hares. Many years ago, experiments were done to investigate the ability of owls of different but related species to detect light and dark mice on either light or dark background, given that owls hunt at night in the dark. The owls caught about half as many mice when they matched the background than when they didn’t—but only when the substrate was complex , with plenty of places for the mice to hide. On bare substrates, there was no difference. Espiritu Santo Island is fairly barren, with extensive bare brown slopes. In this habitat, a dark hare that looks conspicuous to us may be invisible to a night-hunting owl. Variable coloring, in which an individual animal’s coloration changes as the color of its substrate changes, is also seen in some lagomorphs and is a special case of background matching. Snowshoe hares, for example, change color from brown in the summer to white in...