Mimicry, blending into their natural surroundings, helps creatures to survive

The American bittern, often heard but difficult to see, has developed colors that help it blend well into the wetlands in which it hunts. When alarmed it lifts its bill straight up, giving the bird the look of a cattail leaf.

IN THE OUTDOORS • Story and photos by Scot Stewart
“There are two ways to be fooled. One is to believe what isn’t true; the other is to refuse to believe what is true.”
– Søren Kierkegaard

Imagine having to spend your whole life looking over your shoulder and wondering who was eyeing you up as their next meal. Most creatures go through their lives with the belief they could be eaten at any moment. Not only do they need to find food, find a mate and often care for their young, they have to outrun, outfly or outswim everything larger than them who is interested in a meal.
Nevertheless, the world is full of magic. Acts of trickery abound as animals try to stretch out their days as best they can. Animals that are unable to be quick, squeeze into small places, or adequately fight back must seek out other strategies to avoid being something else’s nourishment. The bag of tricks they use is amazingly varied, including cryptic coloration (blending into their environment and attempting to become invisible) and mimicry (appearing to be something they are not). Some rely on protective coloration: colors that warn of poisons or stingers to proudly advertise as a way to warn away possible danger.
For animals in the air or active swimmers, cryptic coloration may simply involve dark dorsal, or top (back) sides and lighter ventral or belly sides. This coloration allows birds, fish, frogs and even swimming garter snakes to blend in with vegetation and the muddy or sandy bottoms of ponds and lakes when seen from above. When viewed from below – in the water looking up or on land or trees looking up at the sky, the light bellies blend in with the light above or the brighter sky.
For large flocks of birds moving in across the sky or over water or schools of fish darting back and forth, turns can help a flock or school match either the dorsal or ventral sides to match the background on either bright or cloudy days, literally causing the entire group to temporarily disappear. This momentary disappearance can give the group the crucial seconds needed to escape a predator in chase.
Some birds take the light top, dark underside strategy to a whole different level. Birds like vireos and some warblers spend most of their time in the treetops feeding on insects where their shading works very well. However, their wings and back are not only darker, but also come in a variety of green shades, helping them blend into the leaves even more efficiently. During the summer months one of the most commonly heard songs across the U.P. is the loud, clear, fluid, “Here I am here, where are you,” of the red-eyed vireo heard endlessly in the tops of poplar, maple and oak trees. As loud and ubiquitous as they are, the red-eyed vireo is rarely seen, because of its ability to blend in. They can continue to seek out mates and defend their nesting territories, often very loudly, with little fear of being caught.
American bitterns add an additional splash to their camouflage. They are medium-sized herons adept at hunting frogs, fish and aquatic invertebrates in bogs and swamps. They are another bird frequently heard, with their strange, deep rusty hand water pump sounding call, but rarely seen. They have streaked brown backs and striped light breasts. When alarmed, they lift their bill into the air giving the bird the look of a cattail leaf amid a cluster of other leaves, allowing them to blend in well when disturbed.
Many animals simply have colors that blend in well with their surroundings due to camouflage patterns. Many species of birds are dimorphic – meaning they have two different forms for male and female. The mallard and the northern cardinal are perfect examples. Males have bright colors – bright green heads for the mallard males, and crimson for the male cardinals. The females are subtly hued, primarily browns for the duck and brownish reds for the female cardinal, allowing them to sit quietly on nests incubating eggs without being seen by predators. But even the bright red of the male cardinal has a safety feature: a brownish tinge to its back. By simply turning away from danger, the cardinal’s back feathers can blend well with the brownish branches of the tree it’s in while it is loudly singing.
The brown creeper is an insect-eating bird fond of probing the crevices in the bark of larger trees. They zoom onto the lower portions of a tree trunk and work their way up the trunk, often reaching near the top before dropping down from the tree and landing on another to begin the process again. The patterns on their backs help them blend seamlessly with the bark of maple, oak, pine, spruce, cherry, hawthorn and other favored trees.
Most moths are nocturnal and extremely inactive during the day time. Some nestle down in the grass or herbs near the ground during the daytime. They may have beautiful brown wings matching fallen leaves or simply fold up their wings to look as small as possible. Others rest on the trunks and branches of trees and rely on cryptic colors to blend in with bark detail and lichens. Underwings must fold their bright orange, red or white striped lower wings to avoid giving further clues to their locations.

The hoverfly has adapted its shape and color to mimic the look of a bumblebee as a self-defense mechanism.

Some moths are diurnal – they are active during daylight hours and feed on unlikely foods like nectar. Sphinx, clearwing and hummingbird moths can hover beside flowers and each use their long mouthpart called a proboscis to draw nectar from the plants. Unlike the large silk moths with no ability to feed and an adult life span of a week or two, these active moths can live up to a month. The sphinx moths mimic the behavior and the clearwing and the hummingbird moths mimic both the behavior and appearance of hummingbirds or baby hummingbirds and may fool predators into leaving them alone
The larger silk moths live only long enough to find a mate, lay eggs and die, but the search for a mate may take days, or at least nights when they are most active. Large moths like the polyphemus, luna and cecropia, some with five-inch wingspreads, can be easily spotted by night predators, including bats, screech and saw-whet owls. To keep these predators off balance a number of moths have “eye” spots with cream or yellow centers and dark edges on their underwings that can be flashed during flight to resemble owl eyes to startle predators and delay attacks, sometimes long enough to escape.
Snowshoe hares and weasels have the ability to change the color of their coats for the season. Both shed their brownish summer coats, suitable for matching fallen leaves and branches in the understory, in favor of bright white winter coats, able to blend with winter snow and reverse the process at the end of winter to brown again. This feature is triggered by the length of light in the day and may not correspond properly with the actual environment, leaving a bright, all-white hare or weasel in a cedar swamp without snow, creating additional challenges for avoiding dangers like barred owls.
Chameleons are true wonders of the animal world, winning the admiration of almost all nature lovers, and the right to star in TV commercials and movies. They are mostly tropical lizards, and like other change artists, such as cephalopods squids and octopi, are not found in the Upper Peninsula, but there are several animals living here with the power to change their colors.
The small goldenrod crab spider here in the U.P. and the white-banded crab spider found to the south are both able to change from yellow to white and back to match the color of flower petals where they wait for nectar-seeking insects. The color changes take time but are reversable. Evidently the change to yellow is easier than the switch to white. The color matching also helps the spiders avoid detection by predators. Mobility of the spiders makes the changeability important. Young crab spiders can balloon from flower to flower finding newly opened flowers more likely to attract bees and butterflies and leave as the flower fades. Older spiders move from flower to flower on the ground. They are unlike many spiders, like the beach wolf spider, gently mottled to blend in with the various shades of sand grain in their habitat and relatively bound to a small hunting territory.
Another animal capable of changing its color as it moves from lichen covered tree branches to ferns and plants like milkweed in the U.P. is the gray tree frog. In a reaction somewhat related to temperature, the frog’s skin can change color to match that of the surface they are on. A hormone in the pituitary gland causes the production of a chemical in skin cells called melanophores, quickly causing the skin color to change and help the frog disappear.
Should that fail, they have a secondary plan to aid their escape. Gray tree frogs have bright orange patches on the underside of their upper rear legs. If turned these patches flash and can surprise an attacking predator, giving the frogs another chance to escape.
One of the best aquatic strategies for becoming invisible comes from a true bug – the water scorpion. It does not have a poisonous stinger on its tail like its namesake, but it does have a snorkel there. The tip of its abdomen is drawn out on its stick-like body allowing it to perch upside-down in the water, the narrow, brown body blending well with stems or sticks. Clinging to a bit of plant life and breathing through its tail, it patiently waits for a tadpole, small fish or insect to swim by.  As its prey draws close, it snaps it forelegs out, much like a praying mantis and grabs it before sucking the fluids from it, in the style of a true bug. The idea of insects eating amphibians or fish is foreign to most, but these insects are true experts at it because of their ability to mimic a bit of a plant. Its appearance quickly draws comparison to another insect, the northern walking stick, found in the far southern parts of the U.P.,Wisconsin and Lower Michigan.
Some animals make fewer attempts to escape. In fact, they are supported by bright colors, like orange and yellow, to announce they have other plans if attacked. Most are familiar with the bright orange, yellow, black or white stripes of bees, wasps and some ants. These are warning colors announcing the insects have stings or bites that can be venomous, painful or even deadly, and should be avoided. A vast array of insects in the insect order Hymenoptera have both the venomous features and the colors.
A number of groups of flies, particularly the surfid and hover flies, have picked up on this warning color concept and have evolved into wasp and bee mimics, with similar stripes and markings. A casual glance at a flower may reveal the sight of a fuzzy yellow and brown insect calmly eating pollen or drinking nectar from the flower. An observer’s initial reaction may be too quickly turn away from a potentially irritated stinging insect , when it simply may be a noisy, but harmless buzzing fly. Another type of hover fly looks similar to a small bee and is sometimes called a sweat bee. It is attracted to human skin and feeds on salts in perspiration. Yet another group of flies, bee flies, have long proboscises and may look like giant mosquitoes or tiny hummingbirds too as they are dark green. Their mouth parts certainly give pause to inspect more closely.
Monarch butterflies, milkweed beetles and milkweed bugs also sport bright orange markings announcing they are poisonous to eat. As they feed, the caterpillars for the monarchs and the nymphs and adults of the milkweed bugs and the milkweed beetles— throughout their lives—accumulate toxins found in the milkweed sap. This diet makes the insects taste badly and usually causes birds to vomit the eaten insects. The birds then learn to avoid eating those species, benefiting the insect species as a whole, though it doesn’t do much to help that first, poor victim. That is the ultimate end of altruism.
The monarch too has a mimic, the viceroy butterfly. In terms of royalty, the viceroy was a stand-in for the monarch – usually the king. The larvae of the viceroy butterfly feeds primarily on willow and is neither poisonous nor bad tasting. Their larvae are mimics of a different kind though, and look like bird droppings, not the bright yellow, white and black striped larvae of the monarchs. But adult has coloration and black markings similar to the monarch’s. Uncertain of its actually identity, birds usually avoid the viceroy as a precaution against getting poisoned.
Nature provides many opportunities to take a second look, at what’s real and what is fake, or at least not what it seems. It is a way to slow things down and enjoy the details of lives well designed and well lived.

Twitter Digg Delicious Stumbleupon Technorati Facebook Email

No comments yet... Be the first to leave a reply!

Leave a Reply

You must be logged in to post a comment.