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1 Displaying your Colors: Animal Coloration and Camouflage Note: These links do not work. Use the links within the outline to access the mages in the popup windows. This text is the same as the scrolling text in the popup windows.. Introduction (Page 1) I. Camouflage (Page 2) Green Insects: This katydid precisely matches the color of the leaves on which it habitually lives. The animal does not change color but rather over many generations there has been selection for a matching color. Lizards: Here are three species of lizards that live on different colored substrates. Note that each one matches the dominant background color of its habitat. Frogs: This light-colored frog lives in trees and matches the color of tree bark. Fish: This is an Australian stonefish. It lies in wait to ambush prey. Its matching of the substrate color disguises it from unwary prey who unknowingly approach it. Its camouflage also can be a problem for humans. When a person reads upon it, stout spines in the dorsal fin of the fish can penetrate one s shoe and deliver venom into the foot. The esulting pain is excruciating and said to be among the worst pain humans ever experience---even worse than corpion stings or childbirth. Persons with stonefish wounds nearly go mad from the pain and sometimes beg to be killed rather than continue to endure it. Heat neutralizes the venom and the antidote is to immerse the foot into water as hot as the patient can endure. Relief is nearly instantaneous. nvertebrates: Here are four invertebrates that match their habitat and are hard to see. In the upper left is a katydid that lives in the eaf litter, in the upper right a crab that lives on pebbled beaches, in the lower left a spider that hides in flowers where t ambushes insects that come to feed on nectar, and in the lower right a bark-inhabiting spider. ndustrial Melanism: The moths seen here are all of the same species. This species has two color variants that can both hatch from the ame clutch of eggs. It lives on the bark of birch trees. In pre-industrial Britain, the birch trunks were light in color and the light-colored variant was hard to see against the light background whereas the darker variant stood out, as hown in the lower frame. Accordingly, birds were able to detect more dark moths than light moths and they preyed upon the darker form with greater intensity than they did upon the lighter one. As a consequence, the darker form became rare while the light one remained common. With the coming of the industrial revolution, the chimneys of Britain s factories spewed out vast quantities of soot that settled on the trees, turning the bark black. Now the black variant matched the background and was hard to see while the lighter one was conspicuous, as shown in the upper rame. Predation by birds then selected for the darker form and against the lighter one with the result that the lighter

2 one became rare and the dark one became common, reversing the previous condition. Later, the trend of selection was reversed once again. Britain established controls that reduced the soot from factories. The trees became light colored again and the dominance of the light variant returned, much as it had been before the industrial revolution. Seasonal:

3 Some habitats change color seasonally, being white with snow in winter and brown or green at other times of year. Thus, animals that match their background at one time of year would be conspicuous at other times, unless they changed color themselves. That is exactly what a number of mammals and birds do, as they shed their hair or eathers and replace them with pelage or plumage of a different hue. The example here is the snowshoe hare that in ummer is brown and matches its background and in winter becomes white and matches the snow. Few Minutes: Chameleons are extraordinary lizards that have the ability to quickly change color and color pattern to match whatever background they temporarily occupy, even adopting colors not normally found in their natural habitat, as hown here. Move: These three photographs are of the same flounder moved onto three backgrounds differing in the size of black figures against a white background. Note that this fish adopts not only the two colors of its background, but adjusts the size of its blotches to correspond to the grain-size of the environment. Transparent: Many marine animals of different phyla are hard to see by virtue of being nearly transparent. There are even ransparent fish! Examples here are an octopus (Phylum Mollusca on the left), two comb-jellies (Phylum Ctenophora n the upper center and upper right), and a crustacean (Phylum Arthropoda in the lower right). Counteract: Fish, such as the one shown here, are good examples of counter-shading. Note that the underside and lower sides ar ighter than the back and upper sides, so that when the fish is viewed from above the dark back matches the depths o he water or the dark bottom, but when viewed from below, the light underside matches the water s bright surface. Disruptive Coloration: n the upper figures the drawing of the snake on the left and on the right are identical. Notice that when the snake is on a uniform background its outline is clearly visible, but that on a variegated background the blotches of the snake and the blotches of the environment are both perceived as individual blotches, not part of a larger entity. The outline of the individual blotches on snake appear much like the blotches in the background but the outline of the snake itself disappears. In the lower right is a real snake, the Gaboon viper, illustrating that point. Its individual blotches are evident, but the outline of the snake is much less clear. In the lower left is a ptarmigan sitting on its nest. It is blotched much as the texture of its environment and is concealed accordingly. The ptarmigan is another species that changes color seasonally. In winter it is white. Other Organisms: This crab has disguised itself by planting algae on its back and as a result looks much like the patch of algae in which t lives. II. Eye-color (Page 3) Conspicuous:

4 Even in such a boldly colored fish as the one shown here, the eye stands out as one of the animal s most conspicuous eatures. Conceal: n this reef fish, the eye is dark and its outline is concealed by a black band that cuts across it and turns down along he side of the face. Mislead: These two fish have a large spot resembling an eye on the posterior end. The real eye is disguised by a dark band unning through it. A would-be predator is likely to mistake the false eye for the real one and attack the less vulnerable tail. Fish would more likely survive an attack on the tail than an assault on the head. mpression: The cobra, with its highly toxic venom, is a formidable adversary when met face to face, but it is vulnerable to attack rom behind when it is raised in this aggressive stance. Most animals try to attack a dangerous opponent from the blind side. These false eyes on the cobra s hood deters such attacks by fooling a would-be attacker into thinking it is being watched. Watched: These two species of caterpillars have conspicuous false eye-spots on the top of the body. In both examples, the head is a tiny object much farther forward and nearly turned under the body; the eyes are tiny and not visible on ither of these photographs. Dangerous: This is a hawk-moth caterpillar that is completely harmless. When undisturbed it is elongated and the visible, upper ide is yellow and it doesn t resemble a snake. When it is disturbed, however, it turns the anterior part of its body over so that the brown underside is exposed, and at the same time it contracts its body muscles and the anterior end o he body swells up to resemble a snake s head. The contraction also pops out false eyes that are folds of skin and have no visual properties whatsoever. In this position, the caterpillar doesn t just look like a snake in general, but it closely resembles a particular species of dangerous viper that lives in the same habitat. Suddenly Displayed: When at rest, these two moths match the color of their background. If, however, they are detected despite their camouflage, conspicuous eyespots are displayed. In the moth on the left the eyespots are seen when the animal is urned over. The moth on the right moves the top pair of wings forward, thereby exposing the back pair of wing with their conspicuous false eyes. Experiments have shown that when predatory birds are confronted by the udden appearance of false eyes, they are deterred in pressing home the attack, at least temporarily. V. Optical illusions (Page 4) Flash-patches: This is a picture of a preserved tropical frog in which the purple patches on the flank have been artificially restored

5 electronically to their color in life. In life, when the frog is sitting normally, its thigh presses against the body and

6 covers up the purple spot. In this position, the frog is camouflaged by matching the color and texture of its background and is extremely difficult to see. If a predator does discover it and the frog hops away, the purple patch causes an optical illusion. As the frog leaps through the air the legs are extended the purple patch is exposed as a lash of color before the leg is again folded against the body as the frog lands That momentary flash distracts the predator and it focuses on the place where the flash occurred whereas the frog continues to move forward. The predator tends to attack the spot where the flash occurred rather than where the camouflaged frog has actually anded. I have personally experienced difficulty in catching this frog, usually grabbing behind it, rather than where it anded, until I realized the problem and corrected for the optical illusion. Butterflies: Stripes: Many fast-moving snakes have longitudinal stripes, such as this Ribbon Snake shown here. A snake with transverse blotches has better camouflage in most habitats than does a striped one. On the other hand, when a blotched snake is moving a predator can track the location of the snake by focusing its eye on one of the blotches. There is no fixed point of reference on a striped snake, particularly one moving rapidly, and the gaze of the predator tends to slide backward along the stripes as the snake moves forward,. Eventually, the predators gaze comes to a point as the tripes converge at the tip of the tail and the predator finds itself staring at the ground where the snake had been, but s now further ahead. Slow snakes tend to depend more on camouflage for protection and are blotched, whereas apid ones tend to rely more on agility and optical illusion and are striped. V. Warning colors (Page 5) Advertising: Many frogs and salamanders have skin secretions that taste bad, cause irritation, or are toxic. Some of them advertise hese noxious qualities by bright, bold patterns, as seen in this drawing. The frog on the left in the upper row has the best of both worlds. It is drab on the upper side and is camouflaged against its background, but if molested and urned over, say by a would-be predator, its brightly colored underside is exposed. Brightly Colored: These beautiful frogs advertise the fact that they are highly toxic, and in fact, have poisons that rank among the most powerful in the world. Some of these are known as arrow poison frogs because native tribes of Central and South America use the secretions from their skins to tip their arrows and blow darts. Deer or other game are killed when he minute amount of poison on the projectile enters their blood stream. Poison from darts that had lain in museums or 15 years was scraped off and found to still be potent. Frogs are second to plants as a source of medicines. Their kin secretions have yielded antibacterial, antifungal and antiviral agents, medicines that are effective against cancer, high blood pressure, low blood pressure and a variety of other disorders, and when all else fails, they are a rich ource of pain killers. VI. Mimicry (Page 6) Venation: Note that the wings of this katydid closely resemble a leaf, even to the pattern of venation on the surface Praying Mantis: These three preying mantis closely resemble leaves and when on a branch are extremely difficult to detect.

7 To the left of center of this photograph you can see a butterfly that resembles a dead leaf on the forest floor where it ives. When it sits still, as it is doing here, it is protected. Only when it spreads its wings to fly, and exposes the colo on top of the wings, does it become conspicuous. Thorns: Some of the thorns you see on this rose bush are real, but others are insects that are mimicking thorns and are shaped and colored exactly like thorns. The insects are homopterans that suck sap out of the stems of the rose. See if you can distinguish the real thorns from the mimics. The insects have legs protruding out of the sides. Seeds: This is a grass stalk with the seeds projecting out at angles from the stem. One of those seeds is really a bug which ooks just like a seed and has positioned itself at the same angle as the seeds. Look carefully and you can identify it by its antennae. Sticks: nsects called walking sticks resemble sticks. On the left is a single individual on a fern leaf. On the right are three of them on a dead branch. Bird Droppings: This caterpillar bears a likeness to bird-droppings on leaves. Leaf-Mimic Butterfly: Bees: Here you can see two insects sucking nectar from the same flower. The one on the left is a moth and cannot sting. I mimics the bumblebee on the right, that can sting. There are also various flies that mimic bees. Wasps: t is hard to find a more exact likeness between two unrelated species, than between this harmless moth on the left and the wasp on the right. The wasp can deliver a nasty sting. Note that the moth resembles the wasp in minute detail of shape and coloration. Venomous: The snake on the left is a venomous coral snake while the one on the right is a harmless king snake. Observe that although the same colors occur in the bands of the two species, they don t occur in the same order. Orchid Flower: This is one of the most unusual cases of mimicry known. There is an insect in which the female produces a scent tha wafts on the breeze. Males downwind of her smell it and fly upwind to mate with her. The orchid flower pictured here, not only mimics the appearance of the female insect, but the scent as well. As a consequence male insects are attracted to the orchid, and being unable to distinguish between the flower and a female of their own species, attempt o make with it. Males that move from one flower to another carry pollen and in their attempts to mate they pollinate he flower.

8 VII. Wolves in sheeps' clothing (Page 7) Ant-mimics: All the individuals pictured here are ants except one. That exception is a spider. Can you tell which one it is? It is he one hanging up-side-down. Examine it closely. You can see three small projections on the tip of the abdomen. Those are the spinnerets, organs that produce spider silk. Ants do not have these. Ants have six legs and a pair of antennae, whereas spiders have eight legs but no antennae. Again, closely examine the spider. You will see that what appear exactly like antennae are not attached to the head in the way they are in ants. Rather they go back and attach to the thorax as legs do. These are the first pair of the spider s legs, which it holds up just like antennae and bends them in just the way the ants do. In this case, the mimicry is not only anatomical and based on color, but nvolves behavior as well. False Cleaner Fish: n order to understand this example of aggressive mimicry, you need to know something about the true cleaner fish. t has a symbiotic relationship with a number of species of fish. It is distinctively shaped, and colored with a conspicuous blue stripe on its side. It performs a looping kind of dance that advertises its cleaning station. Fish glide in and stop and open their mouth and gill covers. The cleaner-fish then enters these cavities and cleans off the mall crustacean parasites that infest most marine fish. The cleaner-fish benefits by getting the parasites for food and he host fish gets rid of its burden of parasites, a mutually advantageous symbiosis. The false cleaner-fish has the ame shape and color pattern as the cleaner-fish and it performs a similar dance. However, when a deceived fish tops at the cleaning station and opens its gill covers, the false cleaner-fish darts in and bites off a hunk of the gills and then rapidly flees the scene. The false cleaner s resemblance to the true cleaner is in anatomy, color and behavior, but with a very different outcome! VIII. Social signals (Page 8) Colored Differently: The birds shown here are cardinals and like many species of birds the female, on the left, is drab whereas the male, on the right, is more brightly colored. The female is camouflaged and protected from predators. The male is more vulnerable to predation, but that disadvantage is offset by other functions of his conspicuous color. Males perch in conspicuous places and sing. Both their appearance and their song have two functions---to attract females as mates, and to warn other males to stay out of the territory. If another male intrudes, the defender of the territory will attack t. Thus, the bright color of the male is a social signal both to females and to males but with an opposite message for he two sexes. Displaying: Many species take the external appearance of the sexes further than merely color differences between males and emales. In some species, the color difference is enhanced by other features such as this crest in a male Cock-of-the- Rock. In many species such accoutrements are emphasized by behavioral means, such as raising the crest, posturing n rather grotesque ways, or performing dances or emitting special calls. Attract: An extreme in ornate coloration is this gaudy male Painted Bunting. Same Signal:

9 This is a male Cuban Anole expanding his throat fan, or dewlap. This signal serves to warn other male anoles to keep out of his territory and also signals his availability to females. When other lizards are not in sight the dewlap is olded up in the throat and can t be seen, rendering the lizard camouflaged. Thus, even male anoles are camouflaged most of the time but only become conspicuous when the social scene demands it.