Adaptive Coloration in Animals is a 500-page textbook about camouflage, warning coloration and mimicry by the Cambridge zoologist Hugh Cott, first published during the Second World War in 1940; the book sold widely and made him famous.
The book's general method is to present a wide range of examples from across the animal kingdom of each type of coloration, including marine invertebrates and fishes as well as terrestrial insects, amphibians, reptiles, birds and mammals. The examples are supported by a large number of Cott's own drawings, diagrams, and photographs. This essentially descriptive natural history treatment is supplemented with accounts of experiments by Cott and others. The book had few precedents, but to some extent follows (and criticises) Abbott Handerson Thayer's 1909 Concealing-Coloration in the Animal Kingdom.
The book is divided into three parts: concealment, advertisement, and disguise. Part 1, concealment, covers the methods of camouflage, which are colour resemblance, countershading, disruptive coloration, and shadow elimination. The effectiveness of these, arguments for and against them, and experimental evidence, are described. Part 2, advertisement, covers the methods of becoming conspicuous, especially for warning displays in aposematic animals. Examples are chosen from mammals, insects, reptiles and marine animals, and empirical evidence from feeding experiments with toads is presented. Part 3, disguise, covers methods of mimicry that provide camouflage, as when animals resemble leaves or twigs, and markings and displays that help to deflect attack or to deceive predators with deimatic displays. Both Batesian mimicry and Müllerian mimicry are treated as adaptive resemblance, much like camouflage, while a chapter is devoted to the mimicry and behaviour of the cuckoo. The concluding chapter admits that the book's force is cumulative, consisting of many small steps of reasoning, and being a wartime book, compares animal to military camouflage.
Cott's textbook was at once well received, being admired both by zoologists and naturalists and among allied soldiers. Many officers carried a copy of the book with them in the field. Since the war it has formed the basis for experimental investigation of camouflage, while its breadth of coverage and accuracy have ensured that it remains frequently cited in scientific papers.
|Adaptive Coloration in Animals|
Cover of first edition
|Author||Hugh Bamford Cott|
Introduction by Julian Huxley
|Illustrator||Hugh Bamford Cott|
|Publisher||Methuen, Oxford University Press|
Adaptive Coloration in Animals is a 500-page book, 10 by 7 inches (250 by 180 mm) in its first edition. It was published by Methuen (in London) and Oxford University Press (in New York) in 1940. It is full of detailed observations of types of camouflage and other uses of colour in animals, and illustrated by the author with clear drawings and photographs. There is a coloured frontispiece showing eight of Cott's paintings of tropical amphibians. The book has 48 monotone plates and several illustrations.[P 1]
Cott's method is to provide a large number of examples, illustrated with his own drawings or photographs, showing animals from different groups including fish, reptiles, birds and insects, especially butterflies. The examples are chosen to illustrate specific adaptations. For example, the fish Chaetodon capistratus is described as follows:[P 2]
this species had the habit of swimming very slowly tail first: but when disturbed it darts rapidly off to safety in the opposite direction... C. capistratus adopts the same tactics... [This fish] is of particular interest in that the real eye is obliterated and a false eye substituted in one and the same animal.— Hugh Cott[P 2]
Cott was well aware that he was publishing in wartime. There are, as Julian Huxley remarks in his 'Introduction', references throughout the book to the human analogues of animal camouflage and concealment. For example, in the section on 'Adaptive Silence', the kestrel is said to "practise dive-bombing attacks", or "after the fashion of a fighter 'plane" to fly down other birds, while "Owls have solved the problem of the silent air-raid"; Cott spends the rest of that paragraph on the "method which has recently been rediscovered and put into practice" of shutting off a bomber's engines and "gliding noiselessly down towards their victims" at Barcelona in the Spanish Civil War.[P 3] In the concluding chapter, Cott explicitly states "The innumerable visible devices used ... in peacetime and in wartime ... are merely rediscovered ... applications of colour that have already reached a high ... degree of specialization and perfection.. in the animal world", mentioning predator-prey relationships, sexual selection and signalling to rivals. He then compares the "hunting disguises put on ... as a means of approaching, ambushing or alluring game, and the sniping suits, concealed machine-gun posts, and booby traps" with the camouflage of animal predators; and similarly he compares "protective disguises" with the "photographer's hide and the gunner's observation post." In the same section, Cott compares intentionally visible signs with animal warning colours: "The policeman's white gloves have their parallel in the white stripes or spots of nocturnal skunks and carabids. The Automobile Association has adopted a system of coloration [black and yellow] whose copyright belongs by priority to wasps and salamanders."[P 4]
The book addresses its subject under three main headings: concealment, advertisement, and disguise.
Cott sets out his view that we have to be re-taught how to see, mentioning Ruskin's "innocence of the eye". He argues that camouflage should, and in animals actually does, use four mechanisms: colour resemblance, obliterative shading (i.e. countershading, the graded shading which conceals self-shadowing of the lower body), disruptive coloration, and shadow elimination.
Chapter 1. General colour resemblance.
Chapter 2. Variable colour resemblance. Caterpillars and pupae (as in Poulton's famous experiment) are coloured to match their environment. Mountain hares change colour in winter; many fish, cephalopods, frogs, and crustacea can change colour rapidly.
Chapter 3. Obliterative shading.
Chapter 4. Disruptive coloration.
The simplified diagrams in Fig. 7 illustrate the value and effectiveness of maximum disruptive contrasts better than any verbal description... On looking at these drawings from a little distance, it will be seen that the conspicuous patches operate most efficiently in distracting attention from the form of the animals wearing them. By sheer force of their brightness, or blackness, or contrasts, they dominate the picture presented to the eye, apparently destroying their form...[P 5]
Cott goes on to explain that the right-hand drawing shows the effect "of broken surroundings in further blending and confusing the picture",[P 5] observing that this is the closest to what is seen in nature. His readers are invited to look first at the right-hand images to gain an idea of the power of "these optical devices" as camouflage, putting off the moment when the animal is actually recognised.[P 6]
Chapter 5. Coincident disruptive coloration.
Chapter 6. Concealment Of the shadow.
Chapter 7. Concealment in defence, mainly as illustrated by birds.
Chapter 8. Concealment In offence.
Chapter 9. Objections and evidence bearing on the theory of concealing coloration.
Chapter 10. The effectiveness of concealing coloration.
Chapter 1. The appearance and behaviour of aposematic animals.
Chapter 2. Warning displays.
Chapter 3. Adventitious warning coloration.
Chapter 4. The nature and function of warning coloration, as illustrated by the mammalia.
Chapter 5. The Protective Attributes Of Aposematic Animals In General.
Chapter 6. The relation between warning colours and distasteful attributes.
Chapter 7. The effectiveness of protective attributes associated with warning colours.
Chapter 8. Experimental evidence that vertebrate enemies learn by experience.
Chapter 9. Evidence of selective feeding by vertebrate enemies in a state of nature.
Chapter 1. Special resemblance to particular objects.
Chapter 2. Adaptive behaviour in relation to special cryptic resemblance.
This wonderful bird ... habitually selects the top of an upright stump as a receptacle for its egg, which usually occupies a small hollow just, and only just, large enough to contain it.... the stump selected had thrown up a new leader just below the point of fracture;... the bird sat facing this in such a way that when viewed from behind they came into line and blended with the grey stem.[P 8]
Chapter 3. Adventitious Concealing Coloration.
Chapter 4. Deflective marks.
Chapter 5. Directive marks.
Chapter 6. Alluring coloration.
Chapter 7. Mimicry: the attributes of mimics.
Chapter 8. Breeding parasitism and mimicry in cuckoos.
The final chapter confirms that "The force of the facts and arguments used in this work is cumulative in effect." Many small steps of reasoning combine to show that "adaptive coloration... has been... one of the main achievements of organic evolution." The book ends by comparing human artefacts and "natural adaptations", both of which can have goals (recall the publication date of 1940, early in the Second World War) including "the frustration of a predatory animal or of an aggressive Power".
Julian S. Huxley wrote a foreword (labelled 'Introduction') which defends the Darwinian concept of adaptation, especially of colour (in animals) and within that frame of mimicry. He makes it clear that "in these last thirty years" (that is, from about 1910 to 1940) he believed that "experimental biologists" professed, even if they did not actually hold, "a radical scepticism on the subject of adaptations", in other words about whether natural selection really could have created the enormous diversity of pattern and colour seen in nature.[P 12] Huxley quoted the now long-forgotten Aaron Franklin Shull's 1936 Evolution which stated "These special forms [sexual selection, warning colours, mimicry and signalling] of the selection idea... seem destined to be dropped, or at least relegated to very minor places in the Evolution discussion.", and more sharply that "aggressive and alluring resemblance" (Huxley's words) "must probably be set down as products of fancy belonging to uncritical times." Huxley's reply is simply[P 12]
Dr. Cott, in this important book, has turned the tables with a vengeance on objectors of this type... Had they taken the trouble to acquaint themselves with even a fraction of the relevant facts to be found in nature, they could never have ventured to enunciate such sweeping criticisms: their objections are a measure of their ignorance.— Julian Huxley[P 12]
With objections dismissed, Huxley remarks that "Dr. Cott is a true follower of Darwin in driving his conclusions home by sheer weight of example," observing that "Faced with his long lists of demonstrative cases, the reader is tempted to wonder why adaptive theories of coloration have been singled out for attack by anti-selectionists." Huxley also noted Cott's "constant cross-reference to human affairs", and that it was good to know that Cott was applying his principles "to the practice of camouflage in war".[P 12]
Huxley concluded his introduction by describing Adaptive Coloration as "in many respects the last word on the subject", upholding the great tradition of "scientific natural history".[P 12]
Reviewers had little to compare Adaptive Coloration with. The English zoologist Edward Bagnall Poulton, a Darwinian, had written a 360-page book, The Colours of Animals, fifty years earlier in 1890, and he was able, at age 84, to review Cott's work in Nature on its appearance in 1940, beginning with the words
This excellent work, eagerly awaited for many years, will be most welcome to naturalists, even, we may hope, to the few who have hitherto rejected the Darwinian interpretation which the author has here supported by a mass of additional evidence based on his own observations and those of very many others.— E.B. Poulton
In this Neodarwinian epic Dr. Cott stamps himself as a true disciple of the master evolutionist. Indeed, he rivals Darwin in the thorough, objective and penetrating analysis of a major biological problem. An immense body of facts and interpretation, much of it original, has been judiciously considered and brought to bear on the question of the biological significance of coloration.— Carl L. Hubbs
Hubbs notes that Cott is seeming concerned about the scarcity of experimental data for the survival value of camouflage, and accordingly relies on Sumner and Isely's "clear-cut results", but at once continues that Cott relies on "the general lore of natural history". Hubbs also remarks on the "resurgence to Darwinian views", referring to the scepticism about the power of natural selection among both geneticists of the time and to the Lamarckist views of Trofim Lysenko.
Hubbs observes that Cott is both an artist and a naturalist as well as a scientist: "In section after section, rivaling one another in fascination, this master of art and of natural history unfolds the biological significance of adaptive coloration in animals." And Cott's emphasis on disruptive patterning and (following Thayer) countershading clearly affected the reviewer: "Particularly impressive is the author's treatment of "coincident disruptive coloration", in which a ruptive mark crosses structural boundaries, so as to obliterate visually such ordinarily conspicuous parts as the eye and the limbs. Concealment of an animal's ordinarily telltale shadow is also stressed". Hubbs's review ends "This book is the work of an artist, and it is a work of art. Every biologist with an interest in any phase of natural history or evolution should keep it at hand."
"W.L.S.", reviewing Cott in The Geographical Journal in 1940, begins with "In this large and well-illustrated volume the author discusses at length reason or reasons for the various colour patterns found in the animal kingdom." The reviewer goes on "He has presented us with a vast number of facts and observations which are somewhat difficult to analyse." However "W.L.S." admits that disruptive coloration "is discussed at considerable length by Mr. Cott and many remarkable instances of it are considered in detail". The review ends by mentioning that while biologists (of the 1930s) usually "reject the influence of Natural Selection in evolution, the facts of adaptive coloration as given in Mr. Cott's work are a strong argument in its favour, and must be given due weight. This is what Mr. Cott claims to have accomplished in a volume which will certainly take its place as a most valuable contribution to zoological literature."
Peter Forbes, in his book Dazzled and Deceived, wrote that
Cott's Adaptive Coloration in Animals must be the only compendious zoology tract ever to be packed in a soldier's kitbag. The book also marks the apotheosis of the descriptive natural history phase of mimicry studies. Although Cott does report experiments on predation to test the efficacy of mimicry and camouflage, the book is essentially a narrative of examples plus theory.
Over 60 years after its publication, Adaptive Coloration in Animals remains a core reference on the subject. Sören Nylin and colleagues observe in a 2001 paper that
Adaptive coloration in animals has been a very active research field in evolutionary biology over the years (e.g. Poulton 1890, Cott 1940, Kettlewell 1973, Sillen-Tullberg 1988, Malcolm 1990), and one in which the Lepidoptera have always featured prominently as model species.— Sören Nylin
As a natural history narrative on what has become an intensely researched experimental subject, Adaptive Coloration could be thought obsolete, but instead, Peter Forbes observes "But Cott's book is still valuable today for its enormous range, for its passionate exposition of the theories of mimicry and camouflage". This width of coverage and continuing relevance can be seen in the introduction to Sami Merilaita and Johan Lind's 2005 paper on camouflage, Background-Matching and Disruptive Coloration, and the Evolution of Cryptic Coloration, which cites Adaptive Coloration no fewer than eight times, quoting his terms "cryptic coloration or camouflage", "concealing coloration", "background matching (also called cryptic resemblance)", "disruptive coloration", resemblance to visual background, and the difficulty a predator has to detect a prey visually.
The zoologist Hugh Cott had the final word in Adaptive Coloration in Animals (1940), a definitive synthesis of everything known about camouflage and mimicry in nature. Cott ruffled fewer feathers [than Trofim Lysenko or Vladimir Nabokov], and his well-organized and unfanatic ideas proved militarily effective, even under the scrutiny of improved techniques for target detection. Thayer’s principles reemerged in more temperate and rational terms, and camouflage schemes based on them survived both photometric analyses and enemy encounters. Biomimetic camouflage took its place as yet another technique in a sophisticated armamentarium of visual deceptions.
Camouflage researcher Roy Behrens cites and discusses Adaptive Coloration frequently in his writings. For example, in his Camoupedia blog, related to the book of the same name, he writes of Cott's drawings of the hind limbs of the Common frog: "Reproduced above is one of my favorite drawings from what is one of my favorite books." He continues "What makes these drawings (and the book itself) even more interesting is that Cott (1900-1987) was not just a zoologist—he was a highly skilled scientific illustrator (these are his own pen-and-ink drawings), a wildlife photographer, and a prominent British camoufleur in World War II." Still in 2011, Behrens can write of Cott's way of thinking, citing his words as models of clear and accurate explanation of the mechanisms of camouflage: "As he so aptly explained it, disruptive patterns work 'by the optical destruction of what is present', while continuous patterns work 'by the optical construction of what is not present.'"
Adaptive Coloration in Animals has been published as follows:
Anti-predator adaptations are mechanisms developed through evolution that assist prey organisms in their constant struggle against predators. Throughout the animal kingdom, adaptations have evolved for every stage of this struggle, namely by avoiding detection, warding off attack, fighting back, or escaping when caught.
The first line of defence consists in avoiding detection, through mechanisms such as camouflage, masquerade, apostatic selection, living underground, or nocturnality.
Alternatively, prey animals may ward off attack, whether by advertising the presence of strong defences in aposematism, by mimicking animals which do possess such defences, by startling the attacker, by signalling to the predator that pursuit is not worthwhile, by distraction, by using defensive structures such as spines, and by living in a group. Members of groups are at reduced risk of predation, despite the increased conspicuousness of a group, through improved vigilance, predator confusion, and the likelihood that the predator will attack some other individual.
Some prey species are capable of fighting back against predators, whether with chemicals, through communal defence, or by ejecting noxious materials. Many animals can escape by fleeing rapidly, outrunning or outmanoeuvring their attacker.
Finally, some species are able to escape even when caught by sacrificing certain body parts: crabs can shed a claw, while lizards can shed their tails, often distracting predators long enough to permit the prey to escape.Blotched emerald
The blotched emerald (Comibaena bajularia) is a moth of the family Geometridae. It is found throughout Europe and the Near East. It has a scattered distribution in England and Wales, but is absent from Scotland and Ireland.Coincident disruptive coloration
Coincident disruptive coloration or coincident disruptive patterns are patterns of disruptive coloration in animals that go beyond the usual camouflage function of breaking up the continuity of an animal's shape, to join up parts of the body that are separate. This is seen in extreme form in frogs such as Afrixalus fornasini where the camouflage pattern extends across the body, head, and all four limbs, making the animal look quite unlike a frog when at rest with the limbs tucked in.
A special case is the disruptive eye mask that camouflages the most conspicuous feature of many animals, the eye.Coloration evidence for natural selection
Animal coloration provided important early evidence for evolution by natural selection, at a time when little direct evidence was available. Three major functions of coloration were discovered in the second half of the 19th century, and subsequently used as evidence of selection: camouflage (protective coloration); mimicry, both Batesian and Müllerian; and aposematism.
Charles Darwin's On the Origin of Species was published in 1859, arguing from circumstantial evidence that selection by human breeders could produce change, and that since there was clearly a struggle for existence, that natural selection must be taking place. But he lacked an explanation either for genetic variation or for heredity, both essential to the theory. Many alternative theories were accordingly considered by biologists, threatening to undermine Darwinian evolution.
Some of the first evidence was provided by Darwin's contemporaries, the naturalists Henry Walter Bates and Fritz Müller. They described forms of mimicry that now carry their names, based on their observations of tropical butterflies. These highly specific patterns of coloration are readily explained by natural selection, since predators such as birds which hunt by sight will more often catch and kill insects that are less good mimics of distasteful models than those that are better mimics; but the patterns are otherwise hard to explain.
Darwinists such as Alfred Russel Wallace and Edward Bagnall Poulton, and in the 20th century Hugh Cott and Bernard Kettlewell, sought evidence that natural selection was taking place. Wallace noted that snow camouflage, especially plumage and pelage that changed with the seasons, suggested an obvious explanation as an adaptation for concealment. Poulton's 1890 book, The Colours of Animals, written during Darwinism's lowest ebb, used all the forms of coloration to argue the case for natural selection. Cott described many kinds of camouflage, and in particular his drawings of coincident disruptive coloration in frogs convinced other biologists that these deceptive markings were products of natural selection. Kettlewell experimented on peppered moth evolution, showing that the species had adapted as pollution changed the environment; this provided compelling evidence of Darwinian evolution.Comatulida
Comatulida is an order of crinoids. Members of this order are known as feather stars and mostly do not have a stalk as adults. The oral surface with the mouth is facing upwards and is surrounded by five, often divided rays with feathery pinnules. Comatulids live on the seabed and on reefs in tropical and temperate waters.Concealing-Coloration in the Animal Kingdom
Concealing-Coloration in the Animal Kingdom: An Exposition of the Laws of Disguise Through Color and Pattern; Being a Summary of Abbott H. Thayer’s Discoveries is a book published ostensibly by Gerald H. Thayer in 1909, and revised in 1918, but in fact a collaboration with and completion of his father Abbott Handerson Thayer's major work.
The book, illustrated artistically by Abbott Thayer, sets out the controversial thesis that all animal coloration has the evolutionary purpose of camouflage. Thayer rejected Charles Darwin's theory of sexual selection, arguing in words and paintings that even such conspicuous animal features as the peacock's tail or the brilliant pink of flamingoes or roseate spoonbills were effective as camouflage in the right light.
The book introduced the concepts of disruptive coloration to break up an object's outlines, of masquerade, as when a butterfly mimics a leaf, and especially of countershading, where an animal's tones make it appear flat by concealing its self-shadowing.
The book was criticised by big game hunter and politician Theodore Roosevelt for its central assertion that every aspect of animal coloration is effective as camouflage. Roosevelt's detailed reply attacked the biased choice of examples to suit Abbott Thayer's thesis and the book's reliance on unsubstantiated claims in place of evidence. The book was more evenly criticised by zoologist and camouflage researcher Hugh Cott, who valued Thayer's work on countershading but regretted his overenthusiastic attempts to explain all animal coloration as camouflage. Thayer was mocked to a greater or lesser extent by other scientific reviewers.Dazzled and Deceived
Dazzled and Deceived: Mimicry and Camouflage is a 2009 book on camouflage and mimicry, in nature and military usage, by the science writer and journalist Peter Forbes. It covers the history of these topics from the 19th century onwards, describing the discoveries of Henry Walter Bates, Alfred Russel Wallace and Fritz Müller, especially their studies of butterflies in the Amazon. The narrative also covers 20th-century military camouflage, begun by the painter Abbot Thayer who advocated disruptive coloration and countershading and continued in the First World War by the zoologist John Graham Kerr and the marine artist Norman Wilkinson, who developed dazzle camouflage. In the Second World War, the leading expert was Hugh Cott, who advised the British army on camouflage in the Western Desert.
The book was well received by critics, both military historians and biologists, and won the 2011 Warwick Prize for Writing.Decorator crab
Decorator crabs are crabs of several different species, belonging to the superfamily Majoidea (not all of which are decorators), that use materials from their environment to hide from, or ward off, predators. They decorate themselves by sticking mostly sedentary animals and plants to their bodies as camouflage, or if the attached organisms are noxious, to ward off predators through aposematism.Disruptive coloration
Disruptive coloration (also known as disruptive camouflage or disruptive patterning) is a form of camouflage that works by breaking up the outlines of an animal, soldier or military vehicle with a strongly contrasting pattern. It is often combined with other methods of crypsis including background colour matching and countershading; special cases are coincident disruptive coloration and the disruptive eye mask seen in some fishes, amphibians, and reptiles. It appears paradoxical as a way of not being seen, since disruption of outlines depends on high contrast, so the patches of colour are themselves conspicuous.
The importance of high-contrast patterns for successful disruption was predicted in general terms by the artist Abbott Thayer in 1909 and explicitly by the zoologist Hugh Cott in 1940. Later experimental research has started to confirm these predictions. Disruptive patterns work best when all their components match the background.
While background matching works best for a single background, disruptive coloration is a more effective strategy when an animal or a military vehicle may have a variety of backgrounds.
Conversely, poisonous or distasteful animals that advertise their presence with warning coloration (aposematism) use patterns that emphasize rather than disrupt their outlines. For example, skunks, salamanders and monarch butterflies all have high-contrast patterns that display their outlines.Disruptive eye mask
Disruptive eye masks camouflage the eyes of a variety of animals, both invertebrates such as grasshoppers and vertebrates including fish, frogs, birds and snakes. They are used by prey, to avoid being seen by predators, and by predators to help them approach their prey. The eye has a distinctive shape and dark coloration dictated by its function, and it is housed in the vulnerable head, making it a natural target for predators. It can be camouflaged by a suitable disruptive pattern arranged to run up to or through the eye, sometimes forming a camouflage eyestripe, as in the Mexican vine snake. The illusion is completed in some animals such as butterflyfish by a false eye or false head somewhere else on the body, in a form of automimicry.
Eye masks were first noticed by the American artist Abbott Handerson Thayer in 1909, and analysed extensively by the zoologist Hugh Cott in 1940. However, in 2005 the evolutionary zoologist Tim Caro could still observe that the assumption that eye masks served as camouflage had not been tested systematically.Distractive markings
Distractive markings serve to camouflage animals or military vehicles by drawing the observer's attention away from the object as a whole, such as noticing its outline. This delays recognition. The markings necessarily have high contrast and are thus in themselves conspicuous. The mechanism therefore relies, as does camouflage as a whole, on deceiving the cognition of the observer, not in blending with the background.
Distractive markings were first noticed by the American artist Abbott Handerson Thayer in 1909, but the mechanism was for a century confused with disruptive coloration, another mechanism for delaying recognition that also relies on conspicuous markings. Distractive markings however need to be small and to avoid outlines, to avoid drawing attention to them, whereas disruptive markings work best when they touch the outline, breaking it up.
Distractive camouflage marks are sometimes called dazzle markings, but the mechanism differs from motion dazzle.Eurasian bittern
The Eurasian bittern or great bittern (Botaurus stellaris) is a wading bird in the bittern subfamily (Botaurinae) of the heron family Ardeidae. There are two subspecies, the northern race (B. s. stellaris) breeding in parts of Europe and Asia, as well as on the northern coast of Africa, while the southern race (B. s. capensis) is endemic to parts of southern Africa. It is a secretive bird, seldom seen in the open as it prefers to skulk in reed beds and thick vegetation near water bodies. Its presence is apparent in the spring, when the booming call of the male during the breeding season can be heard. It feeds on fish, small mammals, fledgling birds, amphibians, crustaceans and insects.
The nest is usually built among reeds at the edge of bodies of water. The female incubates the clutch of eggs and feeds the young chicks, which leave the nest when about two weeks old. She continues to care for them until they are fully fledged some six weeks later.
With its specific habitat requirements and the general reduction in wetlands across its range, the population is thought to be in decline globally. However the decline is slow, and the International Union for Conservation of Nature has assessed its overall conservation status as being of "least concern". Nevertheless, some local populations are at risk and the population of the southern race has declined more dramatically and is cause for concern. In the United Kingdom it is one of the most threatened of all bird species.Flower mantis
Flower mantises are those species of praying mantis that mimic flowers. Their coloration is an example of aggressive mimicry, a form of camouflage in which a predator's colours and patterns lure prey. Most species of flower mantis are in the family Hymenopodidae. Their behaviour varies, but typically involves climbing a plant, and then staying still until a prey insect comes within range (ambush predation). Many species of flower mantis are popular as pets.
The orchid mantis, Hymenopus coronatus, of southeast Asia mimics an orchid flower. It remains motionless on the plant until prey arrive; the same camouflage also protects it from predators. In his 1940 book Adaptive Coloration in Animals, Hugh Cott quotes an account by Nelson Annandale, saying that the mantis hunts on the flowers of the "Straits Rhododendron", Melastoma polyanthum. The nymph has what Cott calls "Special Alluring Coloration" (aggressive mimicry), where the animal itself is the "decoy". The insect is pink and white, with flattened limbs with "that semi-opalescent, semi-crystalline appearance that is caused in flower-petals by a purely structural arrangement of liquid globules or empty cells". The mantis climbs up the twigs of the plant and stands imitating a flower and waits for her prey patiently. It then sways from side to side, and soon various small flies land on and around it, attracted by the small black spot on the end of its abdomen which resembles a fly. When a larger dipteran fly, as big as a house fly, landed nearby, the mantis at once seized and ate it. More recently (2015), the orchid mantis's coloration has been shown to be an effective mimic of tropical flowers; and it has been demonstrated to attract pollinators (as if it were a flower) and then to catch them.Hugh B. Cott
Hugh Bamford Cott (6 July 1900 – 18 April 1987) was a British zoologist, an authority on both natural and military camouflage, and a scientific illustrator and photographer. Many of his field studies took place in Africa, where he was especially interested in the Nile crocodile, the evolution of pattern and colour in animals. During the Second World War, Cott worked as a camouflage expert for the British Army and helped to influence War Office policy on camouflage. His book Adaptive Coloration in Animals (1940), popular among serving soldiers, was the major textbook on camouflage in zoology of the twentieth century. After the war, he became a Fellow of Selwyn College, Cambridge. As a Fellow of the Zoological Society of London, he undertook expeditions to Africa and the Amazon to collect specimens, mainly reptiles and amphibians.Kallima
Kallima, known as the oakleaf or oak leaf butterflies, is a genus of butterflies of the subfamily Nymphalinae in the family Nymphalidae. They are found in east, south and southeast Asia. Their common name is a reference to the lower surface of their wings, which is various shades of brown like a dead leaf.
When the wings are held closed, this results in a remarkable masquerade of a dead leaf, further emphasized by their wing shape.Multi-spectral camouflage
Multi-spectral camouflage is the use of counter-surveillance techniques to conceal objects from detection across several parts of the electromagnetic spectrum at the same time. While traditional military camouflage attempts to hide an object in the visible spectrum, multi-spectral camouflage also tries to simultaneously hide objects from detection methods such as infrared, radar, and millimetre-wave radar imaging.Among animals, both insects such as the eyed hawk-moth, and vertebrates such as tree frogs possess camouflage that works in the infra-red as well as in the visible spectrum.Potoo
Potoos (family Nyctibiidae) are a group of near passerine birds related to the nightjars and frogmouths. They are sometimes called poor-me-ones, after their haunting calls. There are seven species in one genus, Nyctibius, in tropical Central and South America.
These are nocturnal insectivores which lack the bristles around the mouth found in the true nightjars. They hunt from a perch like a shrike or flycatcher. During the day they perch upright on tree stumps, camouflaged to look like part of the stump. The single spotted egg is laid directly on the top of a stump.Self-decoration camouflage
Self-decoration camouflage is a method of camouflage in which animals or soldiers select materials, sometimes living, from the environment and attach these to themselves for concealment.
The method was described in 1889 by William Bateson, who observed Stenorhynchus decorator crabs. It was classified as "adventitious protection" by Edward Bagnall Poulton in 1890, and as "adventitious concealing coloration" or "adventitious resemblance" by Hugh Bamford Cott in 1940, who compared it to the way Australian aborigines stalked waterfowl, covering their faces with water lily leaves.
Among animals, self-decoration is found in decorator crabs, some insects such as caddis flies and the masked hunter bug, and occasionally also in octopuses. In military camouflage, it is seen in the use of ghillie suits by snipers and the helmet nets of soldiers more generally, when these are camouflaged by inserting grass and other local plant materials, and in a more general way by the use of decorated camouflage netting over vehicles, gun emplacements and observation posts.The Colours of Animals
The Colours of Animals is a zoology book written in 1890 by Sir Edward Bagnall Poulton (1856–1943). It was the first substantial textbook to argue the case for Darwinian selection applying to all aspects of animal coloration. The book also pioneered the concept of frequency-dependent selection and introduced the term "aposematism".
The book begins with a brief account of the physical causes of animal coloration. The second chapter gives an overview of the book, describing the various uses of colour in terms of the advantages it can bring through natural selection. The next seven chapters describe camouflage, both in predators and in prey. Methods of camouflage covered include background matching, resemblance to specific objects such as bird droppings, self-decoration with materials from the environment, and the seasonal colour change of arctic animals. Two chapters cover warning colours, including both Batesian mimicry, where the mimic is edible, and Mullerian mimicry, where distasteful species mimic each other. A chapter then looks at how animals combine multiple methods of defence, for instance in the puss moth. Two chapters examine coloration related to sexual selection. Finally Poulton summarizes the subject with a fold-out table including a set of Greek derived words that he invented, of which "aposematic" and "cryptic" survive in biological usage.
The Colours of Animals was well received on its publication, although the book's support for sexual selection was criticised by Alfred Russel Wallace, and its Darwinism and critique of Lamarckism were attacked by Edward Drinker Cope. Wallace liked Poulton's experimental work but was critical of his opinions on sexual selection. The Neo-Lamarckian Cope criticised Poulton's support for Darwin but liked the book's many observations of animal coloration. Modern biologists respect Poulton's advocacy of natural selection and sexual selection, despite the lack at the time of an adequate theory of heredity, and his recognition of frequency-dependent selection.