Camouflage and the light environment

Being spotted by a predator can spell the end for an animal. Camouflage is therefore critical to the survival of many species and is one of the most common anti-predator strategies in nature. An animal's camouflage often depends on matching the colours and patterns of its surroundings, but how can it achieve this when the lighting conditions continually alter the background's appearance? The vegetation and textures in a scene create complex shadows and patterns that rapidly disappear when a cloud passes over and diffuses the lighting. Likewise the colours in a scene depend on atmospheric conditions; on a clear day shadows are blue-tinted, and when overcast the lighting colour becomes uniform. Interactions between lighting conditions and three-dimensional habitat structure could therefore be essential for the success of an animal's camouflage and affect its very survival.

A number of camouflage strategies have been identified that help animals stay unseen, and they often depend on specific lighting conditions. For example, counter-shading is a strategy found in many species that have dark backs and pale underbellies. This coloration helps to cancel out the shadows on the animal's underside, making its tell-tale shape less easily recognised. Coloration that creates false textures and depth cues is also found in many species; tactics that mimic illumination by direct sunlight. Background pattern matching can protect animals from predators, but the background patterns will shift and change throughout the day. It is therefore possible that these strategies become ineffective or even counterproductive under diffuse, overcast conditions. Beyond basic colour differences it remains unknown how these camouflage strategies perform in different light environments and habitat structures; understanding this interaction - which could affect the survival of any visually hunted species - will be the focus of my proposed research.

I plan to use an innovative range of experiments to investigate the importance of three-dimensional habitat structure, colour and lighting conditions on camouflage. First, I will determine whether reed warblers can select nest sites with lighting conditions that optimise the camouflage of their eggs, and test whether a mismatch between egg coloration and lighting increases their likelihood of being spotted by predators. Next, I will create artificial nests in the wild, testing how different camouflage strategies perform given the habitat structure and lighting conditions at the time of predation. Finally, I will use an online evolution game that allows computer-generated 'eggs' to evolve under different lighting conditions and against different backgrounds. I predict that the optimal camouflage strategy should switch depending on how light interacts with the three-dimensional structure of a scene. Flat habitats should favour strategies that create false textures and depth cues, and direct lighting should promote counter-shading and red-green colour matching over blue-yellow.

My research will provide fundamental insights into the importance of lighting conditions and the shape of a habitat on the survival of individual animals. These findings would be of immediate value to conservation projects to develop land-use strategies and farming practices that help protect vulnerable species from predation. Humans are changing the lighting conditions of habitats across the world as a consequence of climate change, potentially altering the efficacy of camouflage strategies that had evolved under different lighting regimes. My research therefore has the potential to open up new areas of research in camouflage, environmental change and conservation.

Conservation and Land Management:
Few habitats in the UK are not visually altered by human behaviour and land use practices. Understanding how vegetation structure and colour affects individual survival therefore has the potential to impact conservation via land-use policy. I will use my links with the British Trust for Ornithology and the Game and Wildlife Conservation Trust, and will contact other relevant organisations (such as Natural England, the National Trust, RSPB, BirdLife International, BugLife, The Woodland Trust, The Forestry Commission, and The Wildlife Trusts), providing them with reports and inviting delegates to a workshop that will disseminate the findings of the proposed research. A working group will then be formed for exploring the practical applications of the findings in land-use strategies and policy.

Industry:
Visual ecology affects animal behaviour, and the ability to hide from view is essential in a number of sectors. The proposed research will develop new models for determining how coloration affects the conspicuousness of a given target, and how the light environment or surrounding features can affect the appearance or behaviour of an animal. These findings will be of immediate relevance to the defence sector, and I will discuss these with representatives from the Defence Science and Technology Laboratory, QinetiQ and the Ministry of Defence by creating contacts and meeting delegates at camouflage conferences. Animal welfare in farming and pest control are other areas that could benefit from the project's output, where, for example the light environment could affect the behaviour of prey, or their camouflaged predators (e.g. creating microhabitats where birds are more comfortable to forage for insect pests, or light environments that reduce stress in livestock).

Public:
Humans are highly visual animals and research into animal coloration is often covered extensively by the popular press and wildlife/nature production companies. The public interest in camouflage and willingness to participate in online 'citizen science' games is pivotal to the proposed camouflage evolution experiment. The game will gather valuable empirical data for the project while simultaneously engaging the public interactively, and offering them further information about the research. The game will attract over ten thousand participants online, and a number of stands will be set up in public spaces to interact with the local community. I have considerable experience in disseminating my research through television, radio and printed/online media outlets, and have attended a course on media communication. I will use my links with production companies to investigate opportunities for disseminating research output, and will further publicise my research through press releases, blog posts, social media and school visits (continuing in my role as STEM ambassador). I will also continue to develop my open source image analysis toolbox which allows anyone to turn a digital camera into a powerful tool for measuring the visual world. Creating an online objective image analysis forum and filming additional 'how-to' videos will continue to allow members of the public to engage with science or pursue their own science projects.

Artists:
Impressionist painters of the nineteenth century developed a new appreciation of how light, shadow and surrounding colours can influence the appearance of a scene long before the importance of these factors were investigated by science and industry. The artist Abbott Thayer later developed many theories of camouflage based his observations of nature that we are continuing to study today. Camouflage is a field where artists and scientists can easily learn from one another, and I have links with a number of artists interested in developing work based on animal vision, and software developers interested in augmented reality and seeing the world through the eyes of another species.