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"Stevens, Martin"
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Cheats and deceits : how animals and plants exploit and mislead
\"Stevens describes the remarkable range of ... adaptations in nature, and considers how they have evolved and increasingly been perfected as part of an arms race between predator and prey or host and parasite. He explores both classic and recent research of naturalists and biologists, showing how scientists find ways of testing the impact of particular behaviours and colourings on the animals it is meant to fool. Drawing on a wide range of examples, Stevens considers what deception tells us about the process of evolution and adaptation\"--Amazon.com.
Book
Sensory Ecology, Behaviour, and Evolution
Throughout their lives, animals must complete many tasks, from finding food, avoiding predators, and attracting mates to navigating through the environment. To do so, they must gather and use a range of information from the world around them and from other individuals. For this, animals have evolved a staggering diversity of sensory organs that are both fundamental to survival and reproduction and shape much of evolution and behaviour. Sensory ecology deals with how animals acquire, process, and use information in behaviour and many other aspects of their lives, and the importance of this in evolution. This book is an introduction to sensory ecology, covering the various sensory modalities across all taxonomic groups. Rather than treating each sensory modality separately, they are discussed together from a behavioural and evolutionary approach with the aim of illustrating key principles and differences across modalities and taxonomic groups. Not only does sensory ecology deal with how the senses work and their use in behaviour, but recent work has also dealt more with the role of sensory systems in evolutionary change, as well as new developments in molecular biology and phylogenetics. The book begins with an introduction to the concepts of information and behaviour, followed by a discussion of the sensory systems that exist, how they work, and features of nerve cells and circuits. It then discusses key issues in communication, and the role of sensory systems and information in larger scale evolutionary processes, such as coevolution and speciation. Throughout the book, examples are given from various modalities and taxonomic groups, relating to diverse areas ranging from anti-predator strategies, foraging, and mate choice to navigation.
eBook
Predator perception and the interrelation between different forms of protective coloration
Animals possess a range of defensive markings to reduce the risk of predation, including warning colours, camouflage, eyespots and mimicry. These different strategies are frequently considered independently, and with little regard towards predator vision, even though they may be linked in various ways and can be fully understood only in terms of predator perception. For example, camouflage and warning coloration need not be mutually exclusive, and may frequently exploit similar features of visual perception. This paper outlines how different forms of protective markings can be understood from predator perception and illustrates how this is fundamental in determining the mechanisms underlying, and the interrelation between, different strategies. Suggestions are made for future work, and potential mechanisms discussed in relation to various forms of defensive coloration, including disruptive coloration, eyespots, dazzle markings, motion camouflage, aposematism and mimicry.
Journal Article
Imperfect camouflage: how to hide in a variable world?
Camouflage is an important anti-predator strategy for many animals and is traditionally thought of as being tightly linked to a specific visual background. While much work focuses on optimizing camouflage against one background, this may not be relevant for many species and contexts, as animals may encounter many different habitats throughout their lives due to temporal and spatial variation in their environment. How should camouflage be optimized when an animal or object is seen against multiple visual backgrounds? Various solutions may exist, including colour change to match new environments or use of behaviour to maintain crypsis by choosing appropriate substrates. Here, we focus on a selection of approaches under a third alternative strategy: animals may adopt (over evolution) camouflage appearances that represent an optimal solution against multiple visual scenes. One approach may include a generalist or compromise strategy, where coloration matches several backgrounds to some extent, but none closely. A range of other camouflage types, including disruptive camouflage, may also provide protection in multiple environments. Despite detailed theoretical work determining the plausibility of compromise camouflage and elucidating the conditions under which it might evolve, there is currently mixed experimental evidence supporting its value and little evidence of it in natural systems. In addition, there remain many questions including how camouflage strategies should be defined and optimized, and how they might interact with other types of crypsis and defensive markings. Overall, we provide a critical overview of our current knowledge about how camouflage can enable matching to multiple backgrounds, discuss important challenges of working on this question and make recommendations for future research.
Journal Article
Pattern mimicry of host eggs by the common cuckoo, as seen through a bird's eye
Cuckoo–host interactions provide classical examples of coevolution. Cuckoos place hosts under selection to detect and reject foreign eggs, while host defences result in the evolution of host-egg mimicry in cuckoos. Despite a long history of research, egg pattern mimicry has never been objectively quantified, and so its coevolution with host defences has not been properly assessed. Here, we use digital image analysis and modelling of avian vision to quantify the level of pattern mimicry in eight host species of the common cuckoo Cuculus canorus and their respective cuckoo host-races. We measure a range of pattern attributes, including marking size, diversity in size, contrast, coverage and dispersion. This new technique reveals hitherto unnoticed sophistication in egg pattern mimicry. We show that various features of host egg pattern are mimicked by the eggs of their respective cuckoo host-races, and that cuckoos have evolved better pattern mimicry for host species that exhibit stronger egg rejection. Pattern differs relatively more between eggs of different host species than between their respective cuckoo host-races. We suggest that cuckoos may have more ‘average’ markings in order to be able to use subsidiary hosts. Our study sheds new light on cuckoo–host coevolution and illustrates a new technique for quantifying animal markings with respect to the relevant animal visual system.
Journal Article
Experimentally generated randomness certified by the impossibility of superluminal signals
From dice to modern electronic circuits, there have been many attempts to build better devices to generate random numbers. Randomness is fundamental to security and cryptographic systems and to safeguarding privacy. A key challenge with random-number generators is that it is hard to ensure that their outputs are unpredictable
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. For a random-number generator based on a physical process, such as a noisy classical system or an elementary quantum measurement, a detailed model that describes the underlying physics is necessary to assert unpredictability. Imperfections in the model compromise the integrity of the device. However, it is possible to exploit the phenomenon of quantum non-locality with a loophole-free Bell test to build a random-number generator that can produce output that is unpredictable to any adversary that is limited only by general physical principles, such as special relativity
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. With recent technological developments, it is now possible to carry out such a loophole-free Bell test
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. Here we present certified randomness obtained from a photonic Bell experiment and extract 1,024 random bits that are uniformly distributed to within 10
−12
. These random bits could not have been predicted according to any physical theory that prohibits faster-than-light (superluminal) signalling and that allows independent measurement choices. To certify and quantify the randomness, we describe a protocol that is optimized for devices that are characterized by a low per-trial violation of Bell inequalities. Future random-number generators based on loophole-free Bell tests may have a role in increasing the security and trust of our cryptographic systems and infrastructure.
1,024 random bits that are uniformly distributed to within 10−12 and unpredictable assuming the impossibility of superluminal communication are generated and certified using a loophole-free Bell test.
Journal Article
Defining disruptive coloration and distinguishing its functions
Disruptive coloration breaks up the shape and destroys the outline of an object, hindering detection. The principle was first suggested approximately a century ago, but, although research has significantly increased, the field remains conceptually unstructured and no unambiguous definition exists. This has resulted in variable use of the term, making it difficult to formulate testable hypotheses that are comparable between studies, slowing down advancement in this field. Related to this, a range of studies do not effectively distinguish between disruption and other forms of camouflage. Here, we give a formal definition of disruptive coloration, reorganize a range of sub-principles involved in camouflage and argue that five in particular are specifically related to disruption: differential blending; maximum disruptive contrast; disruption of surface through false edges; disruptive marginal patterns; and coincident disruptive coloration. We discuss how disruptive coloration can be optimized, how it can relate to other forms of camouflage markings and where future work is particularly needed.
Journal Article
Musculoskeletal pain affects the age of retirement and the risk of work cessation among older people
Many people with chronic pain cannot work, while working despite chronic pain is linked to absenteeism and presenteeism and a host of other deleterious effects. This disproportionately affects older adults, who are closer to retirement, while the exact relationship between pain and work cessation as well as retirement among older adults is not known. We explore longitudinally the relationship between chronic pain and the risk of ceasing work and entering retirement.
Data from 1156 individuals 50 years or older living in England taking part in the English Longitudinal Study of Ageing were used in this study. Cox proportional hazards regression analyses were used to examine the nature of the relationship between musculoskeletal pain and work cessation as well as retirement longitudinally over the course of fourteen years.
Suffering from frequent musculoskeletal pain was associated with an increased risk of ceasing work and retiring at an earlier age, as did work dissatisfaction, higher perceived social status, female gender, and not receiving the recognition they felt they deserved in their job. Severity of depressive symptoms, psychosocial job demands, decision authority, and social support did not influence the age at which participants reported work cessation or retirement.
Frequent musculoskeletal pain may increase the risk of earlier work exit and earlier retirement. Further research should establish the mechanisms and decision making involved in leaving the workforce in people with frequent musculoskeletal pain.
Journal Article
Observing the Average Trajectories of Single Photons in a Two-Slit Interferometer
A consequence of the quantum mechanical uncertainty principle is that one may not discuss the path or \"trajectory\" that a quantum particle takes, because any measurement of position irrevocably disturbs the momentum, and vice versa. Using weak measurements, however, it is possible to operationally define a set of trajectories for an ensemble of quantum particles. We sent single photons emitted by a quantum dot through a double-slit interferometer and reconstructed these trajectories by performing a weak measurement of the photon momentum, postselected according to the result of a strong measurement of photon position in a series of planes. The results provide an observationally grounded description of the propagation of subensembles of quantum particles in a two-slit interferometer.
Journal Article