By Martin Stevens
BBSRC David Phillips Fellow
University of Exeter, UK
Ten years ago, had you asked a random set of biologists working on animal coloration who Abbott Handerson Thayer was, few would have known. Many would have referred to the British zoologist Hugh Cott, the great Victorian naturalist Alfred Wallace, and the Oxford zoologist Edward Poulton as pioneers of the field. While there is no doubt that those individuals are worthy of such recognition, until recently Thayer was largely disregarded. Today, things are very different. Most of Thayer’s key theories have been validated by scientific research over the last ten years, rightfully reinstalling him as the father of camouflage.
At its essence, natural camouflage is a strategy developed by many animal species to stay alive. For some, it is an anti-predator strategy, which hinders a predator in detecting its presence. For many predators, like the preying mantis, camouflage allows them to spring upon their prey unnoticed. Some species like cuttlefish and chameleons can even change color depending on their environment. The principles of camouflage have also found importance in human application, from the battlefield to the hiding of unattractive cell phone towers, and its study is therefore significant. As early as the turn of the 20th century, Thayer realized its potential.
Thayer proposed a great many ideas about animal coloration. Perhaps most importantly, he showed that camouflage is not just about blending into the color and pattern of the surrounding environment, but also about breaking up form and destroying the effect of shadows. He also made it clear that camouflage is context dependent; an animal needs only to be camouflaged at the time and place where it is at risk of detection.
He was well ahead of his time in many other ways as well. Thayer used photographs and practical demonstrations to show the effectiveness of his ideas, rather than simply writing down his thoughts. His talent as a painter and a naturalist helped him greatly to depict how even bright color patches could blend and disappear into the natural environment. His demonstrations to other scientists and the public were similar to the types of displays that modern day scientists use to present their work to the public at events and museums. Interdisciplinary research is also common today, and indeed expected in many cases to bring about new discoveries, so it is a point of unique interest that Thayer’s influence spans zoology, art, and the military.
Thayer made three key contributions to understanding camouflage. The first is usually called countershading, sometimes referred to as “Thayer’s Principle.” The theory of countershading is that animals are normally darker in color on the surface that receives most sunlight and lighter in the areas that receive the least. The effect of this pattern, Thayer concluded, is to cancel out the shadow on the underside of the animal. Poulton first suggested this idea in 18881 with regard to caterpillars, and also in his classic 1890 book The Colours of Animals.2 However, it was independently proposed by Thayer as a “beautiful law of nature,” and he extensively outlined and demonstrated its principles in a paper published in the Auk in 1896.3
Thayer further developed this theory in his book (written with his son Gerald) Concealing Coloration in the Animal Kingdom in 1909,4 and demonstrated its principles with a wide range of photographs, paintings and personal exhibits in the US and Europe, illustrating how objects could “disappear” into the background when they were painted in such a way as to cancel out their shadow. Thayer met Poulton in the UK, and both parties were quick to credit each other with the discovery and shared a range of subsequent correspondence.
It was a remarkable discovery. Countershading as a form of coloration is a widespread phenomenon in nature. Numerous mammals, reptiles, birds, fish, and a variety of invertebrates, including species in both aquatic and terrestrial environments, have darker surfaces and light undersides. Some species of fish even have bioluminescent light-producing organs on the underside of their body to cancel out down-welling light from above (known as counter-illumination). Nonetheless, it was not until scientific studies were conducted between 2004 and 2009 that countershading was shown to really enhance camouflage and hide prey animals from predators.
While there is still more to learn about this phenomenon, scientists today largely agree that countershading has two main benefits in camouflage. The first is to cancel out the shadow that an animal’s body creates on its underside (self-shadow concealment), and the second is to destroy the animal’s three-dimensional shape that would otherwise reveal it to a predator (obliterative shading; Thayer’s original term for countershading). Both have the potential to make an animal, in Thayer’s words, “cease to appear to exist at all.”
The second major contribution Thayer made was his theory of disruptive coloration (referred to as ‘ruptive’ by Thayer). This idea argues that simply matching the background environment is not enough for an animal to remain hidden. Instead, it needs to destroy the appearance of its body outline. Thayer seems to have first written on this in 1903.5 As with countershading, it seems that Poulton actually got there first by discussing ideas akin to disruption in his 1890 book. This was however only in a passing reference, and Thayer was the one who discussed this idea at great length, especially in his book.
Disruptive coloration seems to be found in a wide range of moths, ground-nesting birds like plovers, mammals such as okapi, and numerous fish. It rapidly became a textbook example of camouflage, despite the fact that it lacked any experimental proof. The theory had to wait for validation until 2005, when research showed that disruptive patterns hinder bird predators in finding hidden artificial “moth-like” targets in woodlands. A wide range of subsequent research has shown disruptive coloration to be an important and powerful method of concealment, and we now know how it works in fooling the visual processing of the predator.
Finally, many people are aware of Thayer’s influence and ideas in painting naval vessels during the first and second world war with striking patterns of zigzags, stripes, and blocks of color. The most prominent idea here is that high contrast patterns make it difficult to judge the speed and trajectory of a moving object, termed motion dazzle (after “razzle-dazzle”). In nature, it would mean a predator would fail to attack at the right time to capture its prey. In war, this could mean an enemy targeter misjudging the direction and speed of a moving vessel at which it was firing. This style of ship painting became known as “dazzle painting.” Many of these ideas seem to come from Thayer, as well as from the British painter Norman Wilkinson.
The success of the painting schemes is still debated, and it is even unclear exactly who came up with which ideas. Nonetheless, there are some accounts that suggest the patterns occasionally worked well enough to lead to accidental collisions between vessels.
With the end of World War II and the advent of technology like sonar, dazzle patterns disappeared and the ideas were largely forgotten. Recently, however, scientists have started to ask whether the patterns of animals may have a similar function, most notably the stripes and markings found on some butterflies and other insects, snakes and fish, especially those with stripes that live in shoals. The theory may even provide the answer to the age-old question of why zebra have stripes (and as a point of interest, the collective term for a group of zebra is a “dazzle”).
In the last five years, computer-based experiments using human subjects have shown that stripe and zigzag patterns can indeed make it difficult for us to judge speed and trajectory. It seems that the theory could work, but demonstrating proof in wild animals remains, understandably, quite challenging.
Thayer was a respected and well known artist when he died. But despite the general success of his idea of countershading and his influence on military camouflage, he failed to gain respect and appreciation from zoologists and naturalists for his ideas, or to be taken as seriously as he wanted for his military suggestions. So why were he and his ideas lost for so long from a subject he has taught us so much about?
The problem for Thayer was that, despite his many wonderful theories, they were overshadowed by the unfortunate argument he made that all animals’ coloration was used in concealment. Until recently, the most likely reason for hearing about Thayer would be in an undergraduate biology lecture; students would be shown Thayer’s painting of a group of flamingos, which he insisted were pink to be camouflaged at sunset. We know however that flamingos are not camouflaged. They are seen as dark silhouettes against the setting sun and are strikingly visible throughout the rest of the day. The lecturer would use this as an example of how we need to be careful and rational in our thought process and look for evidence before accepting such ideas as true. Indeed, the case of pink flamingos at sunset was latched onto by the famous American scientist Stephen J. Gould as an example of “illogic and unreason.”6
Thayer had such a strong determination to validate his theories and refute his critics that he sometimes lost the ability to be critical of his own work, taking it to implausible extremes. This does not, however, detract from the fact that many of his theories are valuable contributions to natural history and science. His work is increasingly validated through scientific testing as important principles in camouflage.
Another mistake Thayer made was in his discourtesy to the scientific community of his day. In 19094 Thayer writes in the introduction of Concealing Coloration that the field of protective coloration has “been in the hands of the wrong custodians,” and that “…it has naturally been considered part of the zoologists’ province. But it properly belongs to the realm of pictorial art, and can be interpreted only by painters.” This dismissal of biologists’ contribution to the study of animal coloration, combined with his forceful, sometimes arrogant tone (“Our book presents, not theories, but revelations,” he wrote), may well have conspired to put off many potential advocates of his theories.
Finally, perhaps due to a lack of formal scientific background, Thayer did not always set out his arguments as clearly defined theories and principles (with perhaps the exception of countershading, his most famous theory). He wrote about his ideas of dazzle and ruptive coloration in a continuous and informal prose that makes it hard to fully appreciate the logic of his ideas and, perhaps more importantly, to make predictions from them.
In truth, Thayer’s writing style may reflect the evolving understanding of motion dazzle and disruption, as modern day biologists continue to study these theories and the interrelation between similar concepts. Nonetheless, scientists like to classify and categorize theories in order to neatly test between them. This was something at which Hugh Cott excelled and is one of the reasons his 1940 book on animal coloration remained widely read, while Thayer’s was all but lost. From 1940 until the 21st century camouflage was largely left alone by the academic community, which no doubt also led to a loss of Thayer’s ideas.
Today, however, camouflage is a vibrant area of research. It is a truly interdisciplinary endeavour, studied by biologists, psychologists, computer scientists, military, and even engineers. Thayer’s ideas have been rediscovered and, for the first time, extensively tested. It is somewhat ironic that today he has much of the respect and admiration among scientists that he lacked in his own time.
As the design historian Roy Behrens writes in a paper about Thayer, published in a special issue of the Philosophical Transactions of the Royal Society B in 2009, which is entirely devoted to camouflage: “During his lifetime, he would have needed ‘no introduction’ among serious artists and collectors, yet now … he is largely unknown among artists, art students, and the American public. It is an odd turn of events that his achievements are far more familiar today among zoologists…”7 Perhaps this is where Thayer would want his legacy after all, basking in the field of scientific recognition through his artistic and observational achievement.
Dr. Stevens completed his PhD at the University of Bristol on bird vision and animal camouflage. His current work focuses on sensory ecology and behavior, covering bird color vision, computational models of color and spatial vision, and anti-predator markings.
- Poulton, Edward B. 1888. Notes in 1887 upon Lepidopterous larvae. Trans Entomol Soc Lond. 1888: 595-596.
- Poulton, Edward B. 1890. The Colours of Animals: Their Meaning and Use. Especially Considered in the Case of Insects. Second Edition. The International Scientific Series. London: Kegan Paul, Trench Trübner, & Co. Ltd.
- Thayer, Abbott H. 1896. “The law which underlies protective coloration.” The Auk. 13: 477-482.
- Thayer, Gerald H. 1909. 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. New York: Macmillan.
- Thayer, Abbott H. 1903. “Protective coloration and its relation to mimicry, common warning colours, and sexual selection.” Trans R Entomol Soc Lond. 26: 553-569.
- Gould, Stephen J. 1991. Red Wings in the Sunset. In Bully for Brontosaurus. pp. 209-228. London: Penguin Books.
- Behrens, Roy R. 2009. “Revisiting Abbott Thayer: Non-scientific reflections about camouflage in art, war and zoology.” Phil. Trans. R. Soc. B. 364: 497-502.