Camouflage and survival
By Dr. Robert A. Hedeen, Naturalist
From the beginning of animal life on earth all species have had one thing in commonthe need to find a square meal. And, since every animal is liable at one time or another to be regarded as a source of food by some other animal, survival has depended in a great part on various types of concealment. Natural selection (the survival of the best adapted) has endowed many animals with amazing physical attributes that enable them to escape the sharp eyes of predators, the most notable being natural camouflage.
Camouflage is a means of concealment through the absence of contrast. Camouflaged uniforms and vehicles of military personnel in the field are familiar to us these days, though during the 10 years I served in the Army, neither the field utility uniforms nor vehicles were effectively camouflaged but were an overall dark green in color.
Lack of contrast may be in tone, texture, or color. Thus, a camouflaged rabbit crouching in the weeds, a deer in a forest, or a walking stick on a twig all defy detection by a would-be enemy. Though many animals in addition to man are able to distinguish the various colors of the spectrum, the distinctive shape or silhouette of an individual most often identifies it to another. Birds in the sky often appear only in silhouette, but we recognize them by their shapes and flight patternsthe undulations of the goldfinch and chickadee, the soaring of the vulture and the hawk, and the V formation of geese. Insects too small and too indistinctly marked to be seen clearly at a few yards distance become recognizable as dragon flies, bees, or moths according to clues given by their flight gyrations. This is high contrast, the opposite of camouflage. The silhouette must be eliminated if the animal is to disappear. Two primary adaptations are used to achieve this end:
Disruptive coloration: On its body an animal may wear an irregular pattern of spots, stripes, or other markings that may catch the eye of a would-be predator but draw attention to meaningless details and away from the creatures true outline. This little trick of nature serves to separate a single body into a series of apparently disconnected, unimportant body parts. The spots of a jaguar or fawn and the stripes on a skunk are examples of this very effective means of protection.
Blending coloration: In this type of adaptation to the environment of the species, the animal blends into the general color and texture of the background. Blending and disruptive coloration are sometimes combined and are very effective in affording protection. Of course, to be effective, the animal must keep to the appropriate background if it is to be undetected. A green katydid resting on a red rose petal would be as conspicuous as a crow perched on a snowdrift. If we think about it a minute, most of us are familiar with numerous expressions of this type of camouflage in insects, fish, birds, amphibians, reptiles, birds and mammals.
One cannot help but wonder how many thousands of generations were required for the development of these complex and advantageous adaptations by the awesome forces of natural selection and evolution. A slight advantage in terms of survival potential must have been the test of its permanence because the less effectively camouflaged individuals were selected against and more likely to have been taken as prey and not given the opportunity to be the parents of the next generation. Those with a slight advantage in protective coloration were selected for and were enabled to pass their genetic material on their offspring who, in turn, passed it on to their progeny, and on down the line.
Of course, camouflage alone is not enough to guarantee a success in the never- ending struggle for survival. Defensive adaptations such as fang, claw, hoof, horn, and speed are also very important, but camouflage is one of the more fascinating aspects of the natural history of animals.
Dr. Robert A. Hedeen is a former resident of Marylands eastern shore and resided in the Chicago area from 1960-1971. He is a retired professor emeritus of biological sciences in the University of Maryland system. He has published more than 30 scientific papers, has written numerous magazine articles, and is the author of two books on the natural history of the Chesapeake Bay.