Color in Nature

The Dynamic Role of Hue in the Natural Environment

Whether taking in the splendor of a vivid rainbow against the dark grey-blue of thunderclouds after a summer thunder shower or closely examining an iridescent butterfly wing, color plays a major role in our fascination with the natural environment. The drab brown of a female pheasant or that flash of white from a fleeing deer as it gracefully bounds through the underbrush - all colors play a key role to ensure the survival that particular organism. Without those characteristic pigments, evolution would have phased out the unsuccessful colors and chosen the more successful ones.

The full spectrum of color is a naturally occurring phenomenon, as any color in all its shades and hues can be found in our natural environment. “Color is the result of specific wavelengths of sunlight being reflected from small pigment molecules.” (Williams, E.H. 2005. Pg 64) Color is produced only when “[a] molecule absorbs light . . . and its electrons resonate with the frequency of the incoming wavelengths [and when] other wavelengths are reflected back . . .” (Williams, E.H. 2005. Pg 64)

The sensory abilities of animals to detect certain color patterns have permanently evolved with them. The palette of visible colors varies from animal to animal. Predators would not be able to survive if it they ware unable to detect the coloration of its camouflaged prey. Humans have 3 colors receptors – one each for red, blue, and green. We can only see the colors that these receptors can receive. Other animals have additional color spectrums: birds see ultraviolet colors as well as honeybees, though honeybees lack a red receptor. (Williams, E.H. 2005. Pg 64)

While the role of some pigments are obvious, such as the green of chlorophyll, other colors play different roles in nature. While taking in the glory of a meadow in summer, vibrating with colors from wildflowers, butterflies, and other living organisms, keep in mind that in many cases, colors are “. . .signals, colorful communications from one organism to the other.” (Murphy, P. and Doherty, P. 1996. Pg 20) The flash of yellow from a flitting orange sulfur butterfly, the iridescent blue from a beetle’s wing, that flash of red from a red winged blackbird, and the pink and white stripe from hedge bindweed are all sending signals to each other in one of the most basic of means. Survival has no room for extra and, especially with living organisms, wastes no energy on superfluous displays; all fulfills a vital function.

Color and Animals

While animals come in a variety of shades and hues, coloration is an important adaptation that can mean the difference between life and death. Whether an animal wants to blend in with its environment, such as the spots on a quiet fan fawn, or stand out, such as a squawking blue jay, their coloration is a genetically inherited trait. While there maybe some minor variations that is unique to a certain species, most is predictable.

Most mammals are covered in hair to protect them from the sun’s ultraviolet radiation. Color in animals is determined by pigment groups. Melanin produces browns and blacks. It is the most abundant surface pigment of animals and so creates a high frequency of dark coloration. Hemoglobin produces reds and carotenoids produce yellow, oranges, reddish orange, and pink. Guanine produce whites. Blues and greens are rare in animals, since there is no blue or green pigment, are caused by the interaction of light waves, especially in iridescent colors. Just a few animals, such as the pink of salmon and flamingoes, gain their coloration from the foods they eat. This is known as ingested pigments. (Williams, E.H. 2005. Pg 64) Flamingos gain their pink color from carotenoids found in shrimp. Should shrimp be removed from their diet, they would turn white. (Murphy, P. and Doherty, P. 1996. Pg 36)

The coloration in animals can be categorized, depending upon the function it serves the organism. Camouflage or cryptic coloration enables an animal to become nearly invisible in its surrounding environment. In other words, it allows them to “hide in plain sight”. Cryptic behavior, or the remaining motionless in a concealed area is always accompanied by cryptic coloration. A speckled green frog sitting frozen amongst duckweed in a swampy area is a good example of this coloration. (Williams, E.H. 2005. Pg 64)

A seemingly different color adaptation than cryptic coloration, disruptive coloration helps conceal by breaking up the animal’s outline. (Williams, E.H. 2005. Pg 73) Even though to our eye zebras are a bold black and white stripe, the vision of their predators have difficulty picking out the zebra’s stripes from the tall grasses that it is browsing in. On the other hand, the stripes of a tiger, which is a mix of both blending coloration and disruptive patterns allows it to blend into the long grasses of its natural environment.

Counter shading is the use of different color on the upper and lower body in graduating tones, usually in the form of a light under belly to a dark back. (Williams, E.H. 2005. Pg 71)The presence of spots and stripes are also effective in breaking up the contour of an otherwise solid colored animal. It can also be a means of communication between individual member of the same species. The tail on animals, such as raccoons and red foxes, that are a different color and pattern than the body are used as a means of communication between individual species. These contrasting patterns can be seen from a distance away. “Ringed tails are more common among nocturnal mammals of forest habitats and dark-tipped light tails more common among diurnal mammals of grasslands.” (Williams, E.H. 2005. Pg 72) Contrasting tails also serve as a distraction to predators to lead their attention away from the head.

Aposematic or warning coloration is the use of bold and high contrast coloration in animals that projects a clear message that says “Leave me alone!” This is especially true “with shades of red, orange, yellow, or white contrasted against a black background, [and] usually indicate some kind of noxiousness.” Predators already instinctively know to or quickly learn to avoid these color patterns. (Williams, E.H. 2005. Pg 77) Along with warning coloration comes a negative response, such as a sting from a yellow jacket or the unpalatability of monarch butterflies. A infamous mammal to stay away from, especially if you own a dog, is the black and white stripped skunk.

Yet another and totally different approach to remaining unseen by predators is called the chromatic response. This adaptation enables an otherwise visible organism to change its color to that of its environment, making it almost completely invisible to predators. There are two forms of chromatic response: seasonal chromatic response, as exemplified by the weasel’s ability to change from brown to snowy white in the winter, and rapid chromatic response, which is a more instant and spontaneous reaction, such as the chameleon. Some species of insects have patches of bright color on their wings that remain hidden until disturbed by a predator when the wing is unfolded. This bright flash of color may startle the predator for a second or two, long enough for its prey to escape. (Williams, E.H. 2005. Pg 74)

Albino coloration is produced by the lack of pigmentation in the skin, feathers, hair, and eyes. It occurs when a genetic mutation caused by a recessive trait that makes a pigment producing enzyme, such as melanin in humans, nonfunctional. (Williams, E.H. 2005. Pg 66) An example of this mutation can be found locally, at Cayuga Nature Center, where there is a female albino pheasant in the outside live animal display. However, this coloration, or rather the lack of it, is rare in animals. Lacking protective coloration, these animals become easy prey for predators. Albinism is not found in plants.

Seasonal polymorphism is a term meaning seasonal color changes. In some species of months and butterflies, such as the mustard white butterfly, Spring time coloration is bolder or darker. This adaptation increases the effectiveness of solar warming during basking, an activity essential on cooler mornings. Another adaptation strategy is the ability to become lighter or darker with environmental changes. Some animals have the ability to turn a darker shade in cooler temperature which then makes the absorption of solar heat more efficient. (Williams, E.H. 2005. Pg 82-83)

The colors and patterns of birds have evolved in unison with behavior and is used for both concealment and signaling. Males are more brightly colored than females in order to have a higher visual contrast to their surrounding environment. This serves 2 purposes: to compete with other males and to attract a mate. Brighter plumage means a healthier male, something that female birds instinctively know and seek out during mating season. Conversely, females have drab colors, or cryptic coloration, for protection in raising their young.

Iridescence colors are among the more fascinating of natural phenomenon. The “brilliant, shifting colors and metallic sheens found in nature originate from the interaction of reflected light waves rather than from the solid colors of pigments” (Williams, E.H. 2005. Pg 66) Colors change with the angle at which light is reflected from brilliant sparkling to dark and drab. This is caused by the way light is reflected from microscopic layers of translucent material.

Sunlight is composed of light waves of varying lengths, and the individual color we see is an individual wavelength. “Sunlight also includes light waves that have longer wavelengths than violet light (ultraviolet) and shorter wavelengths than red light (infrared), but [our] eyes can’t detect these frequencies. Since [light] waves are traveling vibrations, rather than physical objects, two waves can be in the same place at the same time.” When an object composed of many very thin layers, such as an abalone shell, sunlight penetrates then reflects off and interferes with each individual layer. The result is the flashing of intense color alternating with shifting hues from drab to brilliant. (Murphy, P. and Doherty, P. 1996. Pg 73)

These fascinating displays of color can be found on birds feathers, butterfly wings, shells, and insects.

In the iridescent head and throat feathers of the ruby throated hummingbird, “colors are visible only from up close – and then only from the right position. From one angle, [they] are a brilliant magenta . . .” But from a different angle, they are drab and dull. “Within the iridescent feathers, a microscope reveals thin layers of pigment separated by air-filled gaps. These submicroscopic structures reflect colors strongly from certain angles.” (Murphy, P. and Doherty, P. 1996. Pg 83)

Butterflies

The wonderful flashes of color seen on the wings of butterflies come from pigments on the powdery scales that cover the wings. Each species has its own distinct set of markings all though individual variation is normal. Both cryptic and disruptive coloration help break up the butterfly’s contour. A well known example of mimicry coloration is the viceroy butterfly copying the black and orange warning coloration of the monarch. Other strategies, such as the false head on a spicebush swallowtail butterfly caterpillar and the eyespots on wood satyr butterfly, serve to distract predators from vital parts of the body where the real thing is located. This tricks a predator into striking the less vital wing instead of the head. It is common on a butterfly with eyespots on its wings to see a wedge-shaped chip missing where a bird was fooled long enough for the butterfly to escape to safety. (Williams, E.H. 2005. Pg 75 - 76)

Butterflies see not only red, blue, green, and violet, but ultraviolet as well. Unlike human vision, butterflies identify themselves by their ultraviolet markings. Ultraviolet colors are iridescent and appear to flicker in light this plays and important role in butterfly behavior and communication.

Rainbows

Rainbows are visible to us because of light that is reflected into our eyes by falling raindrops. One must be standing at a certain angle from the sun in order to see it - always opposite from where you are standing. When light passes though a prism or drop of water at an angle, it refracts, or bends. Each of the colors that make up white light bends at a different angle. This bending causes different colors to bend at different amounts; some colors bend more than others. (Murphy, P. and Doherty, P. 1996. Pg 116 - 118) When sunlight bends, it breaks up into the rainbow colors we see following a rain shower.

Notice that the sky is darker on the outside of the rainbow and lighter on the inside curve. Most of the light reflecting from the raindrops ends up inside the rainbow’s arc, making this area bright. The brightness of the colors indicates the size of the water droplets. Large droplets produce a brilliant rainbow while smaller droplets produce fainter colors. (Murphy, P. and Doherty, P. 1996. Pg 119 -120)

Rain is not the only thing that makes rainbows. Stand at the right angle on a sunny day near your lawn sprinkler or at the base of Taughannock Falls and you’ll be rewarded with a rainbow. If you have a keen eye, set your sights up to the sky on a partly sunny day and you may see Ice crystals in clouds that also creates a pale rainbow.

Sunrise, Sunset

The glowing reds, rose, orange, and yellows we see at sunrise and sunset are caused when sunlight passes through particles in the Earth’s atmosphere, setting off a spectacular display of changing hues. Sunlight has a longer path to follow to penetrate the Earth’s atmosphere than at midday. “In sunshine, all the colors of the rainbow combine to make light we see as white. If air molecules scattered these colors equally, the sky would be as white as a snow bank or the water droplets of a cloud. But, air molecules do not scatter all colors equally.” (Murphy, P. and Doherty, P. 1996. Pg 90)

Some colors scatter more than others due to their individual wavelengths. Colors with shorter wavelengths blue, green, purple are scattered away. Colors with longer wavelengths red, orange, and yellow reach the Earth’s surface. Hence, the colors of our sunsets. Sunrise colors are usually less intense and more pastel because there is water vapor in the atmosphere. Color varies depending upon what particles, both man-made and natural, are in the atmosphere and the actual location. (Murphy, P. and Doherty, P. 1996. Pg 95)

Wildflowers

In the realm of flora, there are three plant color pigments. These include the green of chlorophyll found in leaves and stems, the yellows to reddish orange of carotenoids found in carrots, and the reds and blues anthocyannin of beets, red roses, and blue flowers. (Williams, E.H. 2005. Pg 64) It is also these three pigments that play the staring role in Fall foliage season. The shortening days causes most green plants to cease chlorophyll production, unmasking the other colors caused by presence of carotenoids and anthocyannins in leaves.

Our beloved wildflowers have attained their color because they have co-evolved with their pollinators by adapting specific shapes and displaying certain colors that attracts them to their blooming flower. For example, butterflies prefer red flowers that have a platform for landing. “Bees are attracted to pink, yellow, blue, and distinctly marked flowers, many of which reflect ultraviolet light, sometimes in a bull’s-eye pattern . . .” (Williams, E.H. 2005. Pg 2) Flies, which have poorer vision, prefer saucer-shaped white flowers. “Night feeding moths are attracted to heavy fragrance, but because colors are not visible at night, moth-pollinated flowers are usually pale green or white.” (Williams, E.H. 2005. Pg 2) Bats choose large, pale, and fragrant flowers while beetles go for brightly colored flowers usually with an unpleasant or carrion scented fragrance. “Hummingbirds often choose red, tubular, hanging flowers with abundant nectar.” (Williams, E.H. 2005. Pg 2)

Many wildflowers have stripes, dots, and other bright markings that act like “run-way landing lights” for airplanes. They help guide the pollinator into the part of the flower that has the sweet nectar, the reward for pollen transfer. Brightly colored wildflowers do not waste any energy producing fragrances to attract their pollinators. The honeybee sees the bright orange of butterfly weed much differently than we do because they see it in ultraviolet color.

The level of pH also determines color. Anthocyanins, a pigment common in many plants, “turns red in acid and blue in alkaline conditions.” A good example of this is the hydrangea bushes, in which a gardener will intentionally change the pH of the soil to gain the bright blue color. “Add grape juice to lemonade and it turns bright red. Add the same juice to a mixture of baking soda and water, and it will turn blue.” (Murphy, P. and Doherty, P. 1996. Pg 34) The bright colors along are sufficient for attraction.

As an artist, naturalist, and wildflower lover, I am especially fascinated by the role that color plays in our natural environment. While out hiking, my eye is constantly roving from one side of the path to the other seeking out the color and shape of something interesting. I am delighted to find that giant blue lobelia, cardinal flower, or scarlet pimpernel peeking at me from among the surrounding cloak of green foliage. I hope that this weekend you, too, can find an hour or two to take a hike along a new trail and find a few natural wonders of your own to discover.

Sources:

Williams, E.H. 2005. The Nature Handbook. Oxford University Press. New York, NY

Murphy, P. and Doherty, P. 1996. The Color of Nature. Chronicle Books, San Francisco, Ca.