Crabs' camouflage tricks revealed

MAY 24, 2019

by University of Exeter

Crabs from a single species rely on different camouflage techniques depending on what habitat they live in, new research shows.

University of Exeter scientists compared the colour patterns of common shore crabs (Carcinus maenas) from rock pools with those living on mudflats.

They found that crabs from mudflats closely matched the appearance of the mud they live on, while rockpool crabs did not match the background but instead relied on "disruptive colouration—the use of high-contrast patterns to break up the appearance of the body outline.

Shore crabs are the most common crab found on Britain's coasts, familiar to anyone who goes rock pooling, and the crabs examined in this study came from six sites in Cornwall.

"The crabs are highly variable in colour and pattern, and are often extremely difficult to see," said Professor Martin Stevens, of the Centre for Ecology and Conservation on the University of Exeter's Penryn Campus in Cornwall.

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Bright warning colors on poison dart frogs also act as camouflage

June 4, 2018, University of Bristol

Poison dart frogs are well known for their deadly toxins and bright colours, which have made them a classic example of warning coloration.

The Dyeing Dart Frog, for example, is highly toxic and warns its predators with a bright yellow-and-black pattern.

However, new research led by scientists at the University of Bristol has revealed that the colour pattern does more than simply signal "danger". Counterintuitively, it also works as camouflage.

Lead author, Jim Barnett completed this research, published today in the journal Proceedings of the National Academy of Sciences, while studying for a Ph.D. at Bristol. He is now based at McGill University in Canada.

He said: "Effective as warning signals are, it's not necessarily the best strategy to be maximally conspicuous.

"Certain predators have evolved tolerance of toxins that would be deadly for humans, and some individual predators may have not encountered the warning signal prey before (a dangerous mistake for the predator, but also for the frog).

"So, colour patterns that could be distinctive close-up, but work as camouflage from a distance, would provide a clear advantage."

Combining fieldwork in the jungles of French Guiana, computational modelling, and laboratory visual search experiments, Barnett and colleagues from the University of Bristol's School of Biological Sciences and the School of Experimental Psychology investigated how the Dyeing Dart Frog uses its colours to balance the benefits of effective warning signals with the advantages of concealment.

They found that, despite being highly conspicuous at close range, the particular colours and their arrangement allow the pattern to blend together to form background-matching camouflage when viewed from a distance.

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Beetles' bright colors used for camouflage instead of warning off predators

First study to examine beetle colouration in their natural habitat prompts discovery

Date:  December 4, 2017

Source:  Yale-NUS College

Summary:

Biologists have discovered that the bright color patterns of beetles are not a warning signal to predators as previously believed, but actually a form of camouflage, turning an old assumption on its head.

NUS College Postdoctoral Fellow Eunice Tan has discovered that the bright colour patterns of beetles are not a warning signal to predators as previously believed, but actually a form of camouflage, turning an old assumption on its head. Dr Tan, along with four collaborators from Australia and Spain, examined 51 species of Australian leaf beetles in their natural habitats, and discovered that each beetle's colour pattern is similar to the host plants that the beetle lives on, suggesting that those conspicuous colours help the beetle blend in with the plants it inhabits. The study was recently published as an open-access article in the peer-reviewed journal Frontiers in Ecology and Evolution.

Continued 

Moth’s disguise is so good, spiders love it instead of eating it

26 April 2017

Zoologger is our weekly column highlighting extraordinary animals – and occasionally other organisms – from around the world
 

By Sandhya Sekar

A moth that looks and acts just like a spider is so convincing that it receives elaborate courtship displays from its predator.

Many prey species mimic other poisonous prey or blend into the background to escape predators. The metalmark is one of the few that mimics its predator.

The impersonator’s black, beady “eyes” are actually patterns on its wings, and its “furry legs” are contorted wings with a striped pattern. This gives the impression that it is a big spider. And instead of fluttering like other moths, the metalmark makes jerky leaps like the jumping spiders it mimics.

“It confuses the spider. If the spider is smaller, it even intimidates the spider”, says David Wagner, an entomologist at the University of Connecticut in Storrs, who was not involved in the study. Cannibalism is common in spiders, so smaller ones prefer to run away rather than risk being eaten.

The moths also display a peacock-like behaviour. They raise their forewings and twist their hindwings to show off eyespots and stripes to maximum effect. These appear on the upper and lower surface of the wings, so the moth looks like a spider from the back as well as the front. 

 
Winning combination
To find out which among these strategies – the wing pattern, jerky flight or peacock posture – is most critical for the mimicry to work, Shen-Horn Yen at the National Sun Yat-sen University in Taiwan first presented a Brenthia coronigera to jumping spiders in the lab.

The spiders responded by performing courtship displays, raising and waving their first pair of legs at the moth. Other moths used as a control did not elicit any such response from the spiders – they just got eaten.

“The reason the spider exhibited ‘leg-waving’ behaviour to the moth is that the moth was mistaken by the spider as conspecific,” says Yen.

Read more

In the ocean, clever camouflage beats super sight

Even animals with super sight fail to spot this underwater disappearing trick

Date: August 22, 2016

Source: Duke University

In a matchup of animal superpowers, a clever form of camouflage might beat super sight -- at least in the ocean.

There's nowhere to hide in the open ocean, far from the shore or the seafloor. But some fish have a clever disappearing trick. The silvery skin of fish like herring, sardines, mackerel and tuna act like mirrors, reflecting their watery surroundings to better blend in. The effect serves as a kind of underwater invisibility cloak that helps them hide in plain sight.

Researchers have long assumed that some animals could see through this silvery disguise, thanks to a superpower of their own: the ability to detect a property of light -- called polarization -- that humans can't see.

Octopuses and squid, shrimp and other crustaceans, and some fish such as trout and salmon all have the gift, called polarization vision.

"It's kind of like wearing polarized sunglasses," said Sonke Johnsen, biology professor at Duke University and the first author on a new study of how well animals see reflective camouflage in the ocean.

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Lizards camouflage themselves by choosing rocks that best match the color of their backs

Date:January 25, 2016

Source:University of Cambridge

Resting out in the open on rocks can be a risky business for Aegean wall lizards. Out in these habitats they have nowhere to hide and their backs, which show varying shades of green and brown between individuals, are dangerously exposed to birds hunting in the skies above.

New research by Kate Marshall from the University of Cambridge's Department of Zoology and Dr Martin Stevens from the University of Exeter's Centre for Ecology and Conservation, published today in Scientific Reports, shows that individual lizards are able to choose their resting spot wisely and select a rock in their natural environment that will make their backs less conspicuous to avian predators.

"This suggests that wild individual lizards can choose to rest on the rock they will most resemble, which enhances their own degree of camouflage against visually-oriented predatory birds," says Marshall. "This is the first result of its kind in wild animals, and in lizards specifically."

"One intriguing puzzle remains: how do the lizards 'know' how camouflaged their own backs are to a bird against a particular rock?" She adds.

Other types of lizard, such as chameleons and geckos, are able to rapidly change color in a matter of seconds or minutes to better match their background environment and avoid being spotted by approaching predators. Aegean wall lizards, which are widespread across the South Balkans and many Greek islands, are unable to do this. Instead, this new research shows that they enhance their level of camouflage to hunting birds by choosing to rest on rocks that are more similar in color to that of their own backs.

Birds see the world differently from you or I: for example, they are able to see ultraviolet light whereas we cannot, which means they perceive color (and camouflage) in a very different way. Marshall and her colleagues used visual modelling to test how conspicuous individual lizards would be to a bird's eye against the backgrounds they had chosen to sit on.

Continued ...

Zebras’ stripes not for camouflage, study finds

JANUARY 25, 2016

by Chuck Bednar

Why do zebras have stripes? It was a question we thought we had the answer to – because they serve as camouflage to protect the equine species from predators – but new research published in Friday’s edition of the journal PLOS One suggests that this may not be the case after all.

In the new study, lead author Amanda Melin, an assistant professor of biological anthropology at the University of Calgary, and colleagues from the University of California-Davis explained that the camouflage hypothesis is flawed because it looks at the issue “through human eyes.”

Melin’s team reframed the issue by performing a series of calculations through which they were able to estimate the distances at which lions, spotted hyenas or other zebras could spot the stripes during the daytimes, at twilight or during a moonless night. They found that the stripes could not help the creatures hide, because they would have already been detected in other ways.

“The results from this new study provide no support at all for the idea that the zebra’s stripes provide some type of anti-predator camouflaging effect,” study co-author Tim Caro, a professor of wildlife biology at UC-Davis, explained in a statement. “Instead, we reject this long-standing hypothesis that was debated by Charles Darwin and Alfred Russell Wallace.”

Read more at

Scientists discover new camouflage mechanism fish use in open ocean

November 19, 2015

Scientists have solved a longstanding mystery about how some fish seem to disappear from predators in the open waters of the ocean, a discovery that could help materials scientists and military technologists create more effective methods of ocean camouflage.

In a paper published this week in Science, a team led by researchers at The University of Texas at Austin reports that certain fish use microscopic structures called platelets in their skin cells to reflect polarized light, which allows the fish to seemingly disappear from their predators.

Polarized light is made up of light waves all traveling in the same plane, such as the bright glare you sometimes see when sunlight reflects off the surface of water.

Under the surface of the water, light tends to be polarized. Many fish—and sophisticated modern satellites—have the ability to detect variations in such polarized light.

Read more at:

Crystal amaze: how a chameleon changes colour revealed

Altering the space between tiny crystals allows lizards to reflect a specific wavelength of light and camouflage themselves, study finds

Hannah Devlin, science correspondent

Wednesday 11 March 2015 11.27 GMT

It is one of nature’s most spectacular displays and now scientists have shown how the chameleon changes colour.

A study has found that the lizards possess a layer of skin cells that contain floating nanocrystals. The tiny crystals are roughly evenly spaced throughout the cell and this spacing determines the wavelength of light that the cells reflect.

The latest research shows that chameleons switch colour from green to red by actively changing the spacing between these tiny cellular crystals.

Prof Michel Milinkovitch and his team at the University of Geneva cracked the problem after years of studying the panther chameleon (Furcifer pardalis), native to Madagascar, which has one of the most impressive colour displays in the chameleon kingdom.

Read more ...

Moths shed light on how to fool enemy sonar

Date:

February 18, 2015

Source:

University of Florida

Summary:

It's hard to hide from a bat: The camouflage and mimicry techniques that animals use to avoid becoming a meal aren't much use against a predator using echolocation. But a new study shows that moths can outsmart sonar with a flick of their long tails.

Continued ...

Some like it loud: Warning coloration paved the way for louder, more complex calls in poisonous frogs

Date:

October 25, 2014

Source:

National Evolutionary Synthesis Center (NESCent)

Summary:

Species of poison frogs that utilize bright warning coloration as protection from predators are more likely to develop louder, more complex calls than relatives that rely on camouflage. New research indicates that because these visual cues establish certain species as unsavory prey, they are free to make noisy calls in plain sight and better attract possible mates.

Continued ...

Fast Camouflage: How the Goby Changes Color in One Minute

By Laura Geggel, Staff Writer | October 15, 2014 02:00pm ET

The unassuming rock goby, a small fish that can be found in rock pools around the United Kingdom, southern Europe and North Africa, is a master of camouflage, a new study finds.

Within a minute, the rock goby can change its color and brightness to disguise itself from hungry predators, such as birds and fish.

"These small fish that live in rock pools need excellent camouflage to avoid predators, and because they're often seen against many backgrounds, rapid color change enables them to be hidden in many places quickly," said lead researcher Martin Stevens, a senior research fellow in the Centre for Ecology and Conservation at the University of Exeter, in the United Kingdom.

Read on ...

Spiders Pose as Bird Poop to Evade Predators

By Tanya Lewis, Staff Writer | May 29, 2014 11:57am ET

Many animals camouflage themselves to avoid being eaten by predators, but few are as strange as a spider that disguises itself as bird poop.

The orb-web spider's silver body and the white, silken, disclike decoration on its web give it an uncanny resemblance to bird droppings. The spiders may use this disguise to avoid being captured by predatory wasps, researchers say.

Continued

How Legless, Leaping Fish Living On Land Avoids Predators

Dec. 2, 2013 — One of the world's strangest animals -- a legless, leaping fish that lives on land -- uses camouflage to avoid attacks by predators such as birds, lizards and crabs, new research shows.

UNSW researchers, Dr Terry Ord and Courtney Morgans, of the Evolution and Ecology Research Centre, studied the unique fish -- Pacific leaping blennies -- in their natural habitat on the tropical island of Guam.

Their study will be published in the journal Animal Behaviour.

"This terrestrial fish spends all of its adult life living on the rocks in the splash zone, hopping around defending its territory, feeding and courting mates. They offer a unique opportunity to discover in a living animal how the transition from water to the land has taken place," says Dr Ord, of the UNSW School of Biological, Earth and Environmental Sciences.

Read on

Bad News for Prey: New Research Shows That Predators Can Learn to Read Camouflage

Sep. 10, 2013 — Camouflaged creatures can perform remarkable disappearing acts but new research shows that predators can learn to read camouflage.

The study, which used human subjects as predators searching for hidden moths in computer games, found that the subjects could learn to find some types of camouflaged prey faster than others.

The research was carried out by the University of Exeter and the University of Cambridge and is published in the journal PLOS ONE. Moths with high contrast markings -- that break up the shape of the body, like that of a zebra or giraffe -- were best at evading predation at the start of the experiment. However humans learnt to find these prey types faster than moths with low contrast markings that match the background, like that of a stick insect or leaf bug.

The study shows that the benefit of a camouflage strategy depends on both how well it prevents initial detection and also on how well it inhibits learning.

Lead author Dr Jolyon Troscianko from Biosciences at the University of Exeter said: "This is the first time that a study has focused on the learning of different camouflage types rather than how quickly camouflage prevents initial detection.

"We found considerable differences in the way that predators learn to find different types of camouflage.

"If too many animals all start to use the same camouflage strategy then predators are likely to learn to overcome that strategy more easily, so prey species should use different camouflage strategies to stay under the radar. This helps to explain why such a huge range of camouflage strategies exist in nature."

Read on

Horned ghost crabs change camouflage from day to night

By Ella Davies, Reporter, BBC Nature

Horned ghost crabs change their appearance from day to night for camouflage, a study has revealed.

The species Ocypode ceratophthalmus builds burrows on beaches from Japan to East Africa to shelter from predators.

Researchers investigating young crabs' defences found they fine-tune their brightness to mimic their background.

The crabs reflected changes in their environment throughout the day, becoming lighter in the daytime and darker at night.

The findings are published in the Biological Journal of the Linnean Society.

Horned ghost crabs are named for their eyestalks which extend upwards resembling horns. The crabs are mostly active at night and juveniles are slightly translucent.

Dr Martin Stevens, working for the University of Cambridge, undertook the study with colleagues from the National University of Singapore.

Continued:  http://www.bbc.co.uk/nature/22025789

Tricky Cuttlefish Put on Gender-Bending Disguise

Squid-like cuttlefish are known for their amazing camouflage abilities, thanks to specialized skin cells that allow them to change color in the blink of an eye. Now research finds that these clever mollusks use their color-changing abilities in creative ways: by pretending to be the other gender.

Well, half-pretending, that is.  

When a male cuttlefish is wooing a lady, he often "cheats" by painting typical female patterns on one side of his body, while the other side ? the one facing the female ?  shows off typical male patterns. This gender-bending disguise fools rival males into thinking they're seeing just a couple of ladies hanging out. That means more of an opportunity for the cheater cuttlefish to mate.

Read on:  http://www.livescience.com/21374-cuttlefish-gender-bending-disguise.html

Octopus Foils Predators by Stealing Identities

Instead of blending in with the background, octopuses hide from predators by taking on the shape and color of specific objects in their environment, new research suggests.

"Octopuses are considered to be the master of camouflage. An octopus can change its color, pattern and texture of its skin in an instant," study researcher Noam Josef, of Ben-Gurion University in Israel, told LiveScience.

"By reproducing key features of well-chosen objects, the octopus can produce an effective camouflage that may fool a wide range of potential predators," Josef and colleagues write online today (May 23) in the journal PLoS ONE.

There are a few different ways that animals use camouflage to hide. Some adopt the color or texture of their surroundings, taking in the environment as a whole like, say, a mouse that evolves to have a lighter color because it lives on the beach.

Read on:  http://www.livescience.com/20539-octopus-successful-camouflage.html

Tiny Shark Has Glowing Belly

Tiny sharks about the size of a human hand have a superpower of sorts: their bellies glow, according to new research that also showed these smalleye pygmy sharks use the glow to hide from predators lurking below.

Scientists had proposed the smalleye pygmy shark (Squaliolus aliae) sported light-emitting organs called photophores for use in camouflage, but that was never really tested, said study researcher Julien Claes of the Université catholique de Louvain in Belgium. "It wasn't even known if these organs were really functional, able to produce light," Claes added.

The small shark, which reaches a maximum length of just 8.7 inches (22 centimeters), lives well below the water surface in the Indian and western Pacific Oceans. The new research, detailed this week in The Journal of Experimental Biology, suggests their glowing bellies (a type of bioluminescence) would replace the downwelling light from the sun, or the moon and stars, that is otherwise absorbed by their bodies.

Read more:  http://www.livescience.com/19918-tiny-shark-bioluminescent-belly.html

Cuttlefish Use Humanlike Vision to Choose Camouflage

Here's a tongue-twister for you: Crafty cuttlefish can complete contours to carefully choose camouflage.

What this means, without all the alliteration, is that the visual systems of these squidlike creatures are more sophisticated than previously realized. In fact, cuttlefish can pick the perfect camouflage even without seeing the entirety of what they intend to blend in with, much as humans can translate simple line drawings into meaningful information.

A "disruptive" camouflage pattern used by cuttlefish to blend into "chunky" backgrounds.

CREDIT: Sarah Zylinski, Duke University 

"If you think of our ability to make sense of really basic visual information like cartoons and sketches and children's pictures, we're really good at just using 'edge' information and making sense of it," said Sarah Zylinski, the author of the study and a postdoctoral researcher at Duke University. "It seems that for cuttlefish, too, edges are really important in making sense of the environment."

Read on: http://www.livescience.com/18483-cuttlefish-vision-camouflage.html