A bird attacking a butterfly will often find its beak snapping at thin air. According to our new research, that split-second miss isn’t just bad luck. It’s caused by a visual illusion from the butterfly’s wings.

Our new study, published in the journal Nature (open access), by the University of Exeter and The University of Essex, provides the first evidence that a butterfly’s flight and wing pattern work together to create powerful visual illusions that scramble a predator’s sense of speed and direction, making them misdirect attacks.

It helps solve a long-standing puzzle; butterflies have striking patterns that make them stand out, yet remarkably few predators specialise in catching them mid-flight. Moths, by contrast, are hunted by a wide range of visually guided aerial predators.

“The stripes and spots on many butterflies’ wings interfere with the way visual systems try to guess the direction and speed of moving things, boosting false motion cues while hiding the butterfly’s true heading,” said Dr George Hancock, from the University of Exeter’s Centre for Ecology and Conservation on the Penryn Campus in Cornwall.

“The illusions interfere with the predator’s most basic visual targeting system and disrupt the final ‘ballistic attack’ in the tens of milliseconds when it commits to grabbing its prey, with no time to change course. As a result, birds and other predators will often simply miss.”

Barber-pole effect

The underlying mechanism works much like the “barber-pole illusion” – the red-and-white striped pole outside barber shops, where the stripes appear to travel upward even though the pole is only spinning in place.

“Butterfly wings deform as they fly – clapping together on the upstroke and peeling apart on the downstroke – so their stripes shift angle and point in different directions as they flap,” said Dr Jolyon Troscianko, also from the University of Exeter.

“Combined with their unpredictable flight paths, this patterning creates misleading motion illusions just like the barber-pole, causing a predator to miss entirely, or to strike a less vulnerable part of the wing, such as the hindwing or tail.

“The first slow-motion video of a butterfly I put through our bird-vision computer model was glowing with downwards motion even though the butterfly was moving up.

“First I checked this wasn’t a coding error, that I’d swapped up and down somehow, but then it dawned on me that this would be a perfect way to confuse attacking predators.”

Explainer video

Testing the theory

The team combined multiple lines of evidence. They used a high-speed camera to film real butterflies taking off at over 1,000 frames per second to capture how their patterns behave in flight, as seen through the eyes of a bird.

They then looked at the patterns of around 400 European butterflies and found that motion illusion patterns are widespread. To test how patterns affected real attacks, 100 volunteers acted as “predators”, trying to catch virtual butterflies on a touchscreen.

Finally, they used a computer simulation to “evolve” over 50,000 wing patterns from random starting points, selecting for patterns that created the most motion confusion.

Patterns converged on designs strikingly similar to those found in nature, suggesting that this illusion is a major force shaping butterfly wing evolution.

“It might seem strange that a butterfly would evolve to be so visible, especially as very few European species are toxic or unpalatable,” Dr Hancock said. “But our study reveals the wide variety of different patterns butterflies can use to create illusions that confuse predators.”

Butterflies and moths are also well known for using camouflage while resting, but movement breaks camouflage. This study shows how, once airborne, highly visible butterflies evolved their colours for a completely different line of defence to solve that problem. Beyond butterflies

“The dazzling stripes on zebras and snakes have long been suspected of confusing predators’ motion perception, but firm evidence has been hard to come by,” said Dr Troscianko.

“Our study gives us a genuinely new way to analyse motion vision, and we think motion confusion is likely to be far more widespread in nature than previously realised, from the flapping wings of birds to the flicking tails of lizards and fish. It opens up an exciting new research avenue.”

The study was funded by the Biotechnology and Biological Sciences Research Council.

The paper is entitled: “Butterfly wing patterns in flight create powerful illusory motion cues.”

High-frame-rate videos of butterflies taking flight:

What’s new:

• Detections use rotated (oriented) bounding boxes instead of standard axis-aligned ones
• BehaveAI calculates the angle of each detected object automatically
• Works alongside BehaveAI’s existing motion-based detection and multi-individual tracking

Why it’s useful: Orientation is often the behaviour itself — which way an animal is facing, how it’s turning, whether individuals are aligned with each other or with a stimulus.

BehaveAI is free and open source (AGPL-3.0), built around YOLO, and runs on low-end hardware without a GPU.

BehaveAI GitHub download, User guide

Scientists have used an online game to discover the secrets of animal camouflage—such as why tigers have stripes. The study, by the universities of Exeter and Bristol, reveals that high-contrast markings like tiger stripes are harder to see in sunshine, and in complex 3D habitats such as tall grass or forest undergrowth.

Meanwhile, plainer markings provide better camouflage in indirect sunlight (e.g. under clouds or tree cover) and in simple habitats like short grass.

The results come from a game designed by University of Exeter scientists and played by over 1,000 people. In the game, a patterned sphere “evolved” to become harder to find against various backgrounds and lighting conditions.

The paper, published in the journal PLOS One, is titled “Shining a light on camouflage evolution: using genetic algorithms to determine the effects of geometry and lighting on optimal camouflage.”

“Human vision overlaps with that of many predatory species, so our game is a powerful way to investigate complex questions that are hard to assess in wild animals,” said Dr. George Hancock, from the Center for Ecology and Conservation at Exeter’s Penryn Campus in Cornwall.

“In the game, camouflaged spheres ‘evolved’ over 20 generations, based on how long it took players to find them.

“If a sphere took longer to find, the game used that information to help design the next pattern by combining pairs of the best patterns together.

“In effect, our study used digital evolution to help us understand real-world evolution.”

The background photos where the spheres had to “hide” came from 28 habitats of varying 3D complexity across the UK, pictured in both direct and indirect sunlight.

Under direct sunlight, spheres developed more high-contrast, dark and stripey patterns, countershading (paler underneath like a tiger, antelope or great white shark) and edge disruption (making it harder to see the animal’s outline).

Dr. Hancock said, “We examined something everyone knows but doesn’t think about too often: the fact that the world looks very different on a sunny day.

“When the sun comes out, shadows make the background more visually complex and directional.

“The shadows are stronger and even more directional when the environment is more 3D, such as when there’s taller vegetation.

“This explains how tigers got their stripes: they match the stripe-like shadows within their environment—and similar patterns evolved within our game.

“Equally, plainer patterns—such as those of roe deer—provide better camouflage in places with less direct sunlight and visually simpler habitats.”

Dr. Hancock added that many predators are known to be highly active at dawn and dusk—when long shadows create extra visual complexity.

Dr. Jolyon Troscianko, also from the University of Exeter, said, “Camouflage is essentially a tug-of-war, with both predators and prey investing in various strategies depending on their behavior and environment.”

The researchers say that changes to habitats and lighting—including from land management, urbanization and climate change—could alter the subtle costs and benefits of different camouflage strategies.

“It’s important to understand how such changes might influence animal survival—particularly for species that may already be under threat,” Dr. Troscianko added.

BehaveAI is a biologically inspired video analysis framework that integrates static and motion information through a novel color-from-motion encoding strategy. It converts object movement—direction, speed, and acceleration—into color gradients, meaning both human annotators and pre-trained convolutional neural networks (CNNs) can infer motion patterns while retaining high-resolution spatial details.

Using a range of case studies, we demonstrate how the increased salience of motion information allows for the robust detection of objects that are challenging or impossible to identify reliably from static frames alone, particularly in complex natural scenes. We further demonstrate the reliable classification of different behaviors in animals and single-celled organisms. Additionally, the framework supports flexible hierarchical model structures that can separate the tasks of detection and classification for optimal efficiency, and provide individual tracking data that specifies what is present where and what it is doing in each frame.

The framework makes use of the latest deep learning architecture (YOLO), combined with a semi-supervised annotation workflow. Together with salient motion information, these features can dramatically reduce the effort required for dataset annotation such that reliable models can often be made within an hour. Moreover, smaller annotation datasets mean that model training can be achieved on conventional computers without dedicated hardware, thereby improving accessibility. The motion encoding approach is also computationally lightweight, and can run in real-time on low-end edge devices such as a Raspberry Pi. We release the framework as a free, open source, and user-friendly package.

The paper has just been published in PLoS Biology BehaveAI GitHub download, User guide

Video introduction:

Moths move significantly less when exposed to artificial nighttime light, new research shows. Moths’ attraction to artificial light, such as streetlights, is common knowledge and has been much studied. But, as many people will have observed, moths may also remain still if they land near a light, apparently “trapped.”

To understand this behavior, University of Exeter researchers caught more than 800 moths from 23 species and exposed them to LED lights (of various colors and brightness) or to natural night conditions.

Moths were collected with light traps and butterfly nets on the Penryn Campus grounds, then placed outside in individual pots exposed to one of the light conditions, and filmed to record their movements overnight.

Under 10 lux—a level you might experience near residential streetlighting—moths moved 85% less on average than moths in natural nighttime conditions. This is a big impact on how moths behave, with implications for the time they have for essential activities like finding food or mates.

This could be because the artificial light confuses the moths’ sense of time, causing them to remain still as they do in the daytime, or because the light interferes with their vision.

The study, published in the journal Proceedings of the Royal Society B: Biological Sciences, also found that, at that same 10 lux intensity, amber lighting—commonly thought to be less harmful to insects—reduced moth movement just as much as typical white LEDs.

“Our results suggest that light pollution has widespread effects on nocturnal moth activity, irrespective of lighting type,” said Dr. Emmanuelle Briolat, from the Center for Ecology & Conservation at Exeter’s Penryn Campus in Cornwall.

“This could have important knock-on effects for moth populations and the ‘ecosystem services’ they provide; moths are important pollinators, and a key food source for many other species, from birds to bats.

“Across Europe, moths are in decline, part of a worrying picture of global insect losses, linked to threats like pollution and land-use change—and light pollution could be a significant contributing factor.

“We already know that artificial lighting has many negative impacts on nocturnal insects, and our findings further stress the importance of preserving dark skies.”

Some moth species were even affected by white LED lighting at low levels of 0.1 lux. This is equivalent to indirect “skyglow,” where light from towns and cities illuminates the entire sky across many kilometers, meaning the effects could be more far reaching.

The study also looked at how the activity of moths changed through the course of the night.

Dr. Jolyon Troscianko said, “While we might think that most moths are simply ‘nocturnal’ and active throughout the whole night, we found huge variability among species. Some were most active at the start of the night, others at the end, and most were only ever active for short periods.

“Having such short windows of activity has implications for how artificial light could interfere with the moths’ ability to find food or mates before their short adult lives end. While sitting still under artificial lights won’t kill the moths immediately, these sub-lethal effects could easily add up and prevent them from breeding successfully.”

Paper: Briolat et al. (2026) Severe and widespread reductions in night-time activity of nocturnal moths under modern artificial lighting spectra. Proceedings of the Royal Society B: Biological Sciences, 293

Black arches Resting on a light fitting

Buff arches

The Herald

Mint moth

The Mullein

Poplar hawk-moth

Poplar hawk-moth

Silver Y

Silver Y

But now new research has revealed that the lizards do alter their skin color to blend into their background—just as long as it’s certain colors or shades.

In one of the first laboratory studies of its kind, researchers have identified that the flap-necked chameleon can match yellow, orange, and black backgrounds with much greater accuracy and speed than those that are green or blue.

The study, led by ecologists at the University of Exeter, Cornwall, further reveals that chameleons do not adjust to patterns, in contrast to their portrayal in popular culture. The research has been published this week in the latest edition of Biology Letters.

“Popular culture often depicts chameleons as masters of camouflage, changing their color to match their backgrounds,” says Dr. Jolyon Troscianko of Exeter’s Center for Ecology and Conservation. “We know that they use color changing to communicate with one another, such as during the breeding season, and to regulate their body temperature. But there has been surprisingly little investigation into their approach to concealment beyond some studies on predator threat.”

Chameleons can alter the color of their skin in one of two ways: either through pigment movement or structural color changes within specialized skin cells. And among the different species, the flap-necked chameleon (Chamaeleo dilepis) is renowned for the speed with which it can do this.

For the experiment, eight chameleons were placed individually in a pen that was lined with paper of different colors, hues or pattern treatments. The team then took photographs at timed intervals over two “runs” to measure any change in the animal.

This process was repeated across four colors (yellow, yellow-green, orange and blue-green), three uniform greyscale experiments (black, white, and gray), and six pattern experiments.

“We selected hues that were slightly more colorful than typical natural backgrounds to elicit a stronger response from the chameleons, while still preserving biological plausibility,” said Tom Major, who conducted the research at Exeter but is now part of the Department of Life and Environmental Sciences at Bournemouth University.

“Yellow-green and blue-green colors were selected as those which other chameleons can produce, and orange and yellow could be of ecological relevance to flap-necked chameleons, which experience pronounced dry seasons where leaves and grasses may change to these colors.”

The results revealed that the chameleons responded quickly to blacks, reducing their luminescence to blend into the background much faster than when it was white, all within a matter of minutes.

With the colors, the lizards responded steadily and accurately to yellow, but more slowly and with greater variance to orange. And for yellow-green and blue-green colors, which are closer to the chameleon’s natural appearance, the lizards either didn’t change or did so slowly.

The test also revealed that none of the animals sought to match the pattern, regardless of its color or scale.

All of this analysis took into account what is termed “predator vision modeling”—creating a picture as to whether or not a potential predator, such as the fiscal shrike bird, would be able to distinguish the chameleon against the background.

“This ability to change color is likely to have evolved to enable chameleons to move through diverse habitats, in wet and dry seasons, but remain hidden from their predators,” adds Alexia Hesten, also formerly of Exeter, but now of the School of Biological and Environmental Sciences, at Liverpool John Moores University.

“But a picture is emerging—based upon these results and what we know of other species—that tells us that these famed abilities have their limits and that maybe chameleons favor the kinds of locations that they instinctively know they can match.”

Butterflies that independently evolved the same wing patterns have also evolved similar eyes and brains which are fine-tuned for vision in the shifting light of tropical rainforests, according to new research led by the University of Bristol published in Proceedings of the National Academy of Sciences this week.

Researchers spent two-and-a-half months in the depths of the Amazon rainforest, in one of the most biodiverse regions on Earth—Yasuni National Park in Ecuador—measuring how light varies across the rainforest and linking this to where different species of clearwing butterflies live.

The scientists, led by Dr. Benito Wainwright, former University of Bristol Ph.D. student and 1851 Royal Commission Research Fellow at the University of St Andrews, wanted to investigate whether differences in light under the canopy of the rainforest could have impacted the way the butterflies’ eyes and brains evolved.

The clearwing butterflies are also famous for their mimicry, with multiple species independently evolving the same bold wing patterns to warn predators that they are toxic. Dr. Wainwright describes this as a ‘mutualism,” where both parties benefit.

The research team hoped to gain insight into the consequences this mimicry has on how the clearwing butterfly’s senses evolved.

Dr. Wainwright said, “We discovered that distantly related butterfly species living in the same pockets of rainforest light have evolved remarkably similar visual systems—both their eyes and their brains. Not only that, butterflies that mimic each other’s warning colors tend to live in the same lighting environments, likely enhancing their shared warning signal to predators.

“This shared lifestyle has a powerful knock-on effect—we found that it also shapes how their senses evolve. In other words, species that look alike to scare predators also share similar eyes and brains, and likely see the world in similar ways. This is an astounding example of how mutualisms between species can have a profound impact on steering the course of evolution.”

The research uses the example of tropical butterflies to provide insight into how tropical rainforest communities come together, and how these relationships shape the way animals see the world around them.

By improving our understanding of the factors driving biological diversity, the team hope it will enable better protection of these habitats and predict how they might cope with new environmental challenges.

Dr. Wainwright added, “We are really interested in how changes in the eye and brain match up with changes at the genetic level, and how all these shifts influence the behavior of these butterflies in the wild. Connecting these dots, we can build a more complete picture of how subtle environmental changes can shape the evolution of animal senses.”

While sneaking up on prey, cuttlefish employ a dynamic skin display to avoid detection in the last moments of approach, researchers at the University of Bristol and University of Exeter have found.

Maintaining camouflage while moving is a challenge faced by many pursuit predators. In this study, “Stealth and deception: adaptive motion camouflage in hunting broadclub cuttlefish” published in Science Advances, the team uncovered a novel form of motion camouflage, whereby the broadclub cuttlefish pass dark stripes downward across their head and arms to disguise their hunting maneuvers.

Lead author Dr. Matteo Santon from the University of Bristol’s School of Biological Sciences said, “Camouflage has predominantly been studied as an adaptation that prey use to hamper their detection or recognition from predators, and almost exclusively focused on still prey as motion tends to disrupt camouflage.”

Senior author Dr. Martin How explains, “Most cuttlefish rely on stealth to sneak up on prey. Due to their fast color-changing skin, these remarkable animals have a wider range of options than most when it comes to camouflage while moving.”

By taking a prey crab’s eye-view, the scientists were able to show that the passing-stripe display is camouflaging the predator while hunting. Their findings suggest that the visual system of the prey may be overwhelmed by the strong motion produced by the stripes, causing them to fail to detect the looming cues of the approaching predator.

Dr. Santon added, “To our eyes this dynamic display looks very conspicuous, standing out strongly from the background, but it is exploiting the effect of the strong dynamic motion cues produced by the rhythmic passing stripes to deceive the prey.

“And there is more. This species can produce at least three other types of elaborate hunting displays. This is an astonishing variety of adaptations for sneaking up on prey.”

He now plans to focus on how the other displays function, and to investigate what makes cuttlefish choose one hunting display over another.

He said, “It was a truly magical experience seeing this species hunting in the wild for the first time. Watching this cuttlefish hunting with the passing-stripe display is like being mesmerized by the tricks of a skilled illusionist.”

We exposed moths to shorts bursts of light, simulating car headlights, then observed their flight patterns. We found that the “cool” white phosphor-coated LEDs used in modern car headlights dazzled moths and affected their flight.

Moths exposed to this light were 80% more likely to fly erratically or towards the light, compared to those exposed to other lights—and 25 times more likely to fly in these abnormal ways compared to a control group not exposed to any light.

Moths are important pollinators, pests, and prey. In the UK alone there are over 2,500 species, many of which are showing rapid population declines, with similar trends worldwide.

Light pollution is implicated in their declines and most studies have focused on the effect of streetlights. However, vehicle headlights create intense pulses of light along road networks that extend deep into rural and “dark sky” areas.

“Vehicle headlights are becoming ever brighter and bluer,” said Dr. Jolyon Troscianko, of the Centre for Ecology and Conservation on Exeter’s Penryn Campus in Cornwall. “In humans, our pupils can change size in less than a second in response to dazzling glare, but in insects the process can take tens of minutes, potentially making them highly vulnerable.

“Moths that fly towards car headlights may be killed in a collision, while erratic flight also wastes energy and may increase the risk from predators such as bats. Many moths are only active for a very short time at night, so this disruption could interfere with their ability to feed and find mates.”

We caught and released 428 moths from 64 species on the Penryn Campus, exposing each moth to one of the following for 10 seconds immediately before release:

• “Cool” (blue-shifted) white phosphor-coated LEDs.
• “Warm” (amber-shifted) white phosphor-coated LEDs.
• “Cool” RGB (Red-Green-Blue) LEDs—light from three LEDs of different colors.
• “Warm” RGB LEDs.
• No light (control group).

On release, moths from the light-free control group typically flew either up or down.

Those exposed to the cool phosphor-coated LEDs were more likely to fly towards the light, or in tight circles (something rarely seen in moths when night-lighting is not present).

“Simply by switching to warmer-colored LEDs or different LED technology, we can dramatically reduce their impact on moths,” said Madeleine Fabusova, who collected the data as part of her MSci in Conservation Biology and Ecology at the University of Exeter.

“The phosphor-coated cool LEDs were more harmful than RGB LEDs that have an identical white color to human vision. Our results were remarkably consistent across different moth species. Reducing the blue spectrum in headlights may therefore benefit moths, the flowers they pollinate, and the animals that feed on them.”

Commenting on the trend for brighter, bluer headlights, Professor Kevin Gaston, of the Environment and Sustainability Institute at the University of Exeter, said, “There’s no safety benefit to humans from these blue lights compared to lights with more red and green—the current trends appear to come from car manufacturers.

“Car manufacturers, consumers and policymakers could all play a role in making a fairly simple change to reduce our impact on the natural world.”

Ground-nesting birds called lapwings use the shape of their nests and surroundings to hide from predators, new research shows.

Many ground-nesting species are in decline due to changes in land management and high populations of predators, such as foxes and crows. Conservation projects can fail because too many eggs and chicks are eaten.

The new study, led by the University of Exeter, assessed the visibility of lapwing nests in terms of cover (also called “occlusion”) and camouflage using models that simulate the vision and viewing angles of various predators.

The findings showed that despite nesting in open fields, lapwings can hide their eggs by using small variations in the terrain, making them invisible to ground predators such as foxes from anything more than around 1.5 meters away.

“Like children playing hide and seek, lapwings use cover to complement their camouflage,” said lead author George Hancock, from the Centre for Ecology and Conservation on Exeter’s Penryn Campus in Cornwall.

“If a nest is properly concealed in this way, it doesn’t matter how good a predator’s vision is—they simply won’t be able to see it until they are nearly on top of it.”

“Nests and eggs are also camouflaged—blending in with their surroundings by matching their backgrounds color and pattern—but it appears this is a secondary defense.”

Hancock collaborated with the Game and Wildlife Conservation Trust (GWCT) and used smart phone 3D scanners to measure the shape and height of lapwing nests and their surroundings.

He also used specialized cameras to measure camouflage from the perspective of the lapwing’s predators (foxes, crows and raptors), which can see ultraviolet light.

“Lapwings tended to choose uneven ground for their nests,” Hancock said.

“They selected slightly elevated positions, reducing risk of flooding and allowing them to see predators—without being so high as to stand out to predators.”

Lapwing populations have more than halved since the 1970s.

The findings could help inform conservation efforts for this declining species, which is an iconic part of farmland in the UK and beyond.

“Habitat variation appears to be crucial for allowing lapwings choice in where to nest,” Hancock explained.

“The growth of intensive agriculture has left ground-nesting birds with poorer choices of where to nest.

“Grazed fields provide good habitat, as long as they’re not overstocked with too many grazing animals.”

“New technology is allowing us to better measure how animals see and view the world.”

“Tilled fields can provide really good camouflage for eggs which match the bare earth and can be concealed by the rough geometry, but might be problematic for chicks which are more exposed.”

By providing habitats that compliment lapwing camouflage, Hancock said conservation managers could use “nature’s toolkit”—in addition to direct predator control—to help lapwings breed successfully.

The paper, published in the journal Ecology and Evolution, is entitled “Habitat geometry rather than visual acuity limits the visibility of a ground-nesting bird’s clutch to terrestrial predators.”