Award details

Predator learning of camouflage types

Reference	BB/L017709/1
Principal Investigator / Supervisor	Professor Martin Stevens
Co-Investigators / Co-Supervisors	Dr John Skelhorn
Institution	University of Exeter
Department	Biosciences
Funding type	Research
Value (£)	302,199
Status	Completed
Type	Research Grant
Start date	01/10/2014
End date	30/09/2017
Duration	36 months

Abstract

Most animals face a persistent risk of predation. Correspondingly, prey species have evolved a variety of defensive adaptations, with perhaps the most widespread being camouflage. Camouflage works by preventing detection or recognition of an object. It has long been a key system to understand fundamental questions regarding the evolution, tuning, and mechanistic basis of adaptive traits in nature, and it is a textbook example of natural selection. In the last decade there has been a substantial increase in research effort investigating what types of camouflage exist (e.g. background matching, disruptive coloration), how camouflage works, and the survival benefit that it may confer. This work has been undertaken by evolutionary and behavioural biologists, computer scientists, experimental psychologists, art historians, and the military, and represents a highly interdisciplinary subject. Despite numerous advances, most work has been focussed on how different camouflage types prevent initial detection. However, in reality, most predators will encounter the same or similar prey types frequently over a period of hours and days, allowing them the opportunity to learn to discriminate prey from the background and subsequently form search images. Because the success of a camouflage strategy will be affected by how effectively it prevents initial detection, learning and search image formation, there is currently a major gap in our understanding of how camouflage works. Here, we use humans searching for hidden targets on touch screens, and domestic chicks searing for artificial prey in arenas, as model predator systems. We will determine whether different camouflage types are easier to learn than others or more resistant to predator search images. We will also test what specific prey features (e.g. pattern contrast, spatial frequency, and disruptiveness) facilitate or hinder search image formation, and how findings are consistent between humans and birds.

Summary

Most animals face a persistent and significant risk of predation. Correspondingly, prey species have evolved a wide variety of defensive strategies, often including protective coloration. Perhaps the most widespread anti-predator defence is animal camouflage. Camouflage works by preventing detection or recognition of an object, and is also valuable to human applications and recreation. It has long been a key textbook example of natural selection, but in the last decade there has been a substantial increase in research investigating what types of camouflage exist, how they work, and the survival benefit conferred. This work has been undertaken by evolutionary and behavioural biologists, computer scientists, experimental psychologists, art historians, and the military, and represents a highly interdisciplinary subject. Several types of camouflage have been studied, including background matching (resembling the colour and pattern of the background environment), disruptive coloration (high contrast markings at the body edges that break up the shape of the body), and distractive markings (high contrast isolated markings that may draw the predator's attention towards them and away from the body edge). Despite numerous advances most work has focussed on how different camouflage types prevent initial detection in predators that have not seen the prey before. However, in reality, most predators will encounter similar prey types repeatedly over a period of hours and days, allowing them the opportunity to learn to discriminate prey from the background, and giving them the opportunity to form 'search images' (by selectively paying attention to particular features of the prey's appearance). These search images temporarily increase a predator's ability to find one prey type but decrease its ability to find other prey types. Currently, although learning and search image effects have been investigated in some camouflage studies, almost no work has specifically tested how differenttypes of camouflage and specific features of prey patterns facilitate and affect predator learning and search image formation. Because the success of a camouflage strategy will be affected by how it prevents both initial detection as well as learning and search image formation, there is currently a major gap in our understanding of how camouflage works and the value of different camouflage types. Here, we use humans searching for hidden targets on touch screens, and domestic chicks searching for hidden artificial prey in arenas, as model predator systems to test how the value of different types and features of camouflage are affected by predators' experience of different prey types. These systems allow us to precisely control prey features and the experience of the subjects acting as predators. Specifically, we will: 1) Determine whether some camouflage types are easier to learn than others by presenting human and chicks with prey types and measuring how effectively detection times decrease over repeated encounters. 2) Determine whether some camouflage types are more resistant to predator search images than others by presenting humans and birds with sequences of the same prey type to test how quickly they form search images, and whether this affects their ability to find prey of other types later. 3) Determine what specific prey features (e.g. pattern contrast, pattern size, and disruptiveness) facilitate search image formation. 4) Test whether findings are consistent between humans and birds by using comparable experiments with birds and humans to determine how the principles about camouflage and visual search and detection can be applied across species. This project would answer key questions in camouflage research, including how different types of concealment affect learning and search image formation, the nature of search images and which prey features predators attend to, and whether the principles are consistent among taxonomic groups.

Impact Summary

1) Public outreach, education, and widening participation. Predator-prey relationships and animal coloration are subjects with a long history of captivating public interest and attention, and have great potential to inspire future generations about science and learning. The general concepts are readily understandable and easy to demonstrate, as well as being striking and highly visual. Camouflage has long been a key textbook example of natural selection and is frequently covered in the popular media. This interest has significantly increased in recent years, with the subject regularly being covered in television and radio programmes, art and design exhibitions, and several recent popular science books. The PI has a wide range of experience dealing with media interest (both reactive and proactive), setting up websites on our research, and corresponding Twitter and Facebook accounts for disseminating our work in social media (see Pathways to Impact). A key aim of ours is to communicate with and inspire the general public, especially school children and young adults about the subject and science in general. To this end, we will: i) coordinate with press offices about press releases from our papers and communicating our research in general, ii) apply to present a display at the Royal Society Summer Science Exhibition, iii) make an interactive website explaining our work to a broad audience, as well as computer games demonstrating the key concepts of our work, alongside a downloadable phone/tablet app, iv) give talks at various public/outreach events, in particular to local schools, and v) set up a Facebook and Twitter account to disseminate our work and interesting materials, and the subject area in general, to a wide audience. 2) Economic and commercial. Camouflage has also long had significant importance in human application, such as the military, and recreation and commerce, including art, wildlife watching, and hunting. In addition, it is increasingly used in an urban environment to disguise functional but unattractive objects such as mobile phone transmission masts and satellite dishes. The PI currently co-supervises a CASE studentship part funded by the MoD on motion camouflage. Our work will provide information about how objects can be camouflaged in complex real world environments to different receivers (birds and humans). In addition, our work may also be relevant to advertising and packaging of products. We will investigate how colour patterns can hide objects and prevent observers from learning about them. By turning these principles around, we can understand how to make objects maximally conspicuous and easy to remember. When we have obtained sufficient results to make early findings we will coordinate with relevant departments, the MoD, and industry about the application and exploitation of our work and its potential relevance to products.

Committee	Research Committee A (Animal disease, health and welfare)
Research Topics	Animal Welfare, Neuroscience and Behaviour
Research Priority	X – Research Priority information not available
Research Initiative	X - not in an Initiative
Funding Scheme	X – not Funded via a specific Funding Scheme

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