disruptive eye mask
   HOME

TheInfoList



OR:

Disruptive eye masks are
camouflage Camouflage is the use of any combination of materials, coloration, or illumination for concealment, either by making animals or objects hard to see, or by disguising them as something else. Examples include the leopard's spotted coat, the ...
markings that conceal the eyes of an animal from its
predator Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill th ...
s or prey. 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 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 comb ...
arranged to run up to or through the eye, sometimes forming a camouflage eyestripe. The illusion is completed in some animals by a false eye or false head somewhere else on the body, in a form of
automimicry In zoology, automimicry, Browerian mimicry, or intraspecific mimicry, is a form of mimicry in which the same species of animal is imitated. There are two different forms. In one form, first described by Lincoln Brower in 1967, weakly-defended m ...
. Disruptive eye masks are seen on a variety of animals, both invertebrates such as
grasshopper Grasshoppers are a group of insects belonging to the suborder Caelifera. They are among what is possibly the most ancient living group of chewing herbivorous insects, dating back to the early Triassic around 250 million years ago. Grasshopp ...
s and
vertebrate Vertebrates () comprise all animal taxa within the subphylum Vertebrata () ( chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, ...
s, including
fish Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of li ...
,
frog A frog is any member of a diverse and largely Carnivore, carnivorous group of short-bodied, tailless amphibians composing the order (biology), order Anura (ανοὐρά, literally ''without tail'' in Ancient Greek). The oldest fossil "proto-f ...
s,
birds Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweigh ...
and
snake Snakes are elongated, Limbless vertebrate, limbless, carnivore, carnivorous reptiles of the suborder Serpentes . Like all other Squamata, squamates, snakes are ectothermic, amniote vertebrates covered in overlapping Scale (zoology), scales. Ma ...
s. Eye masks were first noticed by the American artist
Abbott Handerson Thayer Abbott Handerson Thayer (August 12, 1849May 29, 1921) was an American artist, naturalist and teacher. As a painter of portraits, figures, animals and landscapes, he enjoyed a certain prominence during his lifetime, and his paintings are represen ...
in 1909, and analysed extensively by the zoologist
Hugh 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 especia ...
in 1940. However, in 2005 the evolutionary zoologist
Tim Caro Timothy M. Caro (born 1951) is a British evolutionary ecologist known for his work on conservation biology, animal behaviour, anti-predator defences in animals, and the function of zebra stripes. He is the author of several textbooks on these su ...
could still observe that the assumption that eye masks served as camouflage had not been tested systematically.


History

The American artist
Abbott Handerson Thayer Abbott Handerson Thayer (August 12, 1849May 29, 1921) was an American artist, naturalist and teacher. As a painter of portraits, figures, animals and landscapes, he enjoyed a certain prominence during his lifetime, and his paintings are represen ...
mentioned the "masking" of the eyes of birds and mammals in his 1909 book ''
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 191 ...
'', stating that this was found mainly in birds, such as
plover Plovers ( , ) are a widely distributed group of wading birds belonging to the subfamily Charadriinae. Description There are about 66 species in the subfamily, most of them called "plover" or "dotterel". The closely related lapwing subfa ...
s, and predatory mammals. He noted that "it is very effective .. as it completely breaks the eye's otherwise conspicuous circular or oval outline. The zoologist
Hugh 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 especia ...
identified the value of concealing the eye in his 1940 book ''
Adaptive Coloration in Animals ''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 ...
''. He notes the "inherent conspicuousness of an eye-spot", which "stands out from everything else, and rivets the attention", making the point with a diagram containing one small eyespot and many larger features: the eyespot immediately attracts the viewer's attention. The image has been used elsewhere, for example in Tim Newark's 2007 book on
camouflage Camouflage is the use of any combination of materials, coloration, or illumination for concealment, either by making animals or objects hard to see, or by disguising them as something else. Examples include the leopard's spotted coat, the ...
, where Newark noted that Cott's image proved the point, as "the eye of a vertebrate, with its dense black pupil, stands out from the most jumbled backgrounds, as Cott's illustration demonstrates." Cott argued that "no scheme of camouflage will be completely effective which does not mask or modify the appearance of the eye". He mentioned, as "beautiful examples" of face patterns that achieve this, the swamp viper and the
Gaboon viper The Gaboon viper (''Bitis gabonica''), also called the Gaboon adder, is a viper species found in the rainforests and savannas of sub-Saharan Africa.McDiarmid RW, Campbell JA, Touré T. 1999. ''Snake Species of the World: A Taxonomic and Geograp ...
. In his words: Cott described disruptive eye masks as a special case of a
coincident disruptive pattern 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 ...
, one that provides camouflage by joining together parts of the body to create a new appearance which contradicts the actual structures present. On camouflage eyestripes, he noted that "more or less well-defined ocular bands or stripes" are found in many species of bird, including the
nuthatch The nuthatches () constitute a genus, ''Sitta'', of small passerine birds belonging to the family Sittidae. Characterised by large heads, short tails, and powerful bills and feet, nuthatches advertise their territory using loud, simple songs. Mo ...
,
snipe A snipe is any of about 26 wading bird species in three genera in the family Scolopacidae. They are characterized by a very long, slender bill, eyes placed high on the head, and cryptic/camouflaging plumage. The ''Gallinago'' snipes have a near ...
, whimbrel,
ringed plover The common ringed plover or ringed plover (''Charadrius hiaticula'') is a small plover that breeds in Arctic Eurasia. The genus name ''Charadrius'' is a Late Latin word for a yellowish bird mentioned in the fourth-century Vulgate. It derives from ...
, and
turnstone Turnstones are two bird species that comprise the genus ''Arenaria'' in the family Scolopacidae. They are closely related to calidrid sandpipers and might be considered members of the tribe Calidriini. The genus ''Arenaria'' was introduced by t ...
, and thought it significant that these patterns were associated with active young that leave the nest early, as in the ringed plover. He recorded that "what appear to be markings of similar significance" are found in
mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or ...
s such as
gemsbok The gemsbok or South African oryx (''Oryx gazella'') is a large antelope in the genus ''Oryx''. It is native to the extremely dry, arid regions of Southern Africa; notably, the Kalahari Desert. Some authorities formerly classified the East Afric ...
,
sable antelope The sable antelope (''Hippotragus niger'') is an antelope which inhabits wooded savanna in East and Southern Africa, from the south of Kenya to South Africa, with a separate population in Angola. Taxonomy The sable antelope shares the genus ''Hi ...
,
Grant's gazelle Grant's gazelle (''Nanger granti'') is a species of gazelle distributed from northern Tanzania to South Sudan and Ethiopia, and from the Kenyan coast to Lake Victoria. Its Swahili name is ''swala granti''.vizcacha Viscacha or vizcacha (, ) are rodents of two genera (''Lagidium'' and ''Lagostomus'') in the family Chinchillidae. They are native to South America and convergently resemble rabbits. The five extant species of viscacha are: *The plains vis ...
. In 1989, J. L. Cloudsley-Thompson noted that camouflage eyestripes are also found in many reptiles including slender arboreal vine snakes, numerous tropical fish such as the angelfish and
garfish The garfish (''Belone belone''), also known as the garpike or sea needle, is a pelagic, oceanodromous needlefish found in brackish and marine waters of the Atlantic Ocean and the Mediterranean, Caribbean, Black, and Baltic Seas. Description Th ...
, and a wide variety of amphibians including the
common frog The common frog or grass frog (''Rana temporaria''), also known as the European common frog, European common brown frog, European grass frog, European Holarctic true frog, European pond frog or European brown frog, is a semi-aquatic amphibian o ...
. The evolutionary zoologist
Tim Caro Timothy M. Caro (born 1951) is a British evolutionary ecologist known for his work on conservation biology, animal behaviour, anti-predator defences in animals, and the function of zebra stripes. He is the author of several textbooks on these su ...
observed in 2005 that "the whole topic of disruptive coloration needs systematic analysis". Caro noted that in mammals, "no systematic tests of this idea are available", but that dark patches around the eyes, which would tend to draw attention to the eye instead of camouflaging it, are associated with grassland and terrestrial carnivores as well as
riparian A riparian zone or riparian area is the interface between land and a river or stream. Riparian is also the proper nomenclature for one of the terrestrial biomes of the Earth. Plant habitats and communities along the river margins and banks ar ...
animals, suggesting the function of reducing glare, or perhaps of
aposematism Aposematism is the advertising by an animal to potential predators that it is not worth attacking or eating. This unprofitability may consist of any defences which make the prey difficult to kill and eat, such as toxicity, venom, foul taste or ...
.


Pattern

G. W. Barlow, noting Cott's examples, analysed fish "eye-lines" in 1972, finding a relationship between angle of line and both body shape and angle of forehead. He found that fast-swimming species had longitudinal lines and long bodies; deep-bodied fish had vertical bars and the ability to turn abruptly. Many barred patterns were in his opinion "obviously an adaptation for crypsis" (camouflage). He concluded that stripes and bars were both
social signal Within evolutionary biology, signalling theory is a body of theoretical work examining communication between individuals, both within species and across species. The central question is when organisms with conflicting interests, such as in sex ...
s and
antipredator adaptation 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 avo ...
s. In 1981, Leah and Benjamin Gavish tested patterns that conceal birds' eyes using patterns and human observers. They found that patterns which allow the eye to protrude from the dark area concealed the eye best, calling this the "borderline eye effect". Some animals such as
butterflyfish The butterflyfish are a group of conspicuous tropical marine fish of the family Chaetodontidae; the bannerfish and coralfish are also included in this group. The approximately 129 species in 12 genera are found mostly on the reefs of the Atlant ...
combine the camouflaging of the eye with an eyespot somewhere else on the body, possibly giving the impression that the animal's head is located there. In 2013, Karin Kjernsmo and Sami Merilaita showed using artificial prey and predatory fish (
three-spined stickleback The three-spined stickleback (''Gasterosteus aculeatus'') is a fish native to most inland and coastal waters north of 30°N. It has long been a subject of scientific study for many reasons. It shows great morphological variation throughout its ra ...
s) that such eyespots diverted predators' attacks from the vulnerable head. File:Elegant Grass-mimicking Grasshopper (Leptacris elegans) (14008906395) (cropped).jpg, Elegant grass-mimicking grasshopper has stripes that join head and eye to the body File:Equetus lanceolatus in Madagascar Reef.jpg, The jack-knifefish has a strongly disruptive pattern on body and through the eye. File:Bep chaetodon oxycephalus.jpg, The eye of the spot-nape butterflyfish is concealed by a bold eyestripe. File:Four-Eye Butterflyfish.jpg, In the four-eye butterflyfish, eyestripe camouflage is combined with a conspicuous eyespot near the tail. File:Tail-spot butterflyfish 8 (cropped).jpg, The tail-spot butterflyfish is conspicuously coloured, but its eye is camouflaged and the tail has a false eye, adding to the illusion by distracting predators' attention from the head. File:2014.07.17.-28-Zadlitzgraben Pressel--Grasfrosch-Weibchen.jpg, The
common frog The common frog or grass frog (''Rana temporaria''), also known as the European common frog, European common brown frog, European grass frog, European Holarctic true frog, European pond frog or European brown frog, is a semi-aquatic amphibian o ...
has a
disruptively patterned 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 comb ...
body and an eyestripe concealing the eye. File:Sitta europaea wildlife 2 1.jpg, The
Eurasian nuthatch The Eurasian nuthatch or wood nuthatch (''Sitta europaea'') is a small passerine bird found throughout the Palearctic and in Europe. Like other nuthatches, it is a short-tailed bird with a long bill, blue-gray upperparts and a black eye-stripe. ...
has a stripe joining the beak, eye, and body File:Oxybelis aeneus (detail).jpg, The
Mexican vine snake ''Oxybelis aeneus'', commonly known as the Mexican vine snake or brown vine snake, is a species of Colubridae, colubrid snake, which is Endemism, endemic to the Americas. Geographic range and habitat ''O. aeneus'' is found from within the Atasc ...
has a dark, strongly contrasting eyestripe to conceal the eye. File:Oryx gazella - Etosha 2014.jpg,
Gemsbok The gemsbok or South African oryx (''Oryx gazella'') is a large antelope in the genus ''Oryx''. It is native to the extremely dry, arid regions of Southern Africa; notably, the Kalahari Desert. Some authorities formerly classified the East Afric ...
has a disruptive facial mask that obscures the eye.


References


Sources

* * * {{Camouflage Camouflage