Graeme Ruxton

Graeme Ruxton
University of St Andrews · Centre for Biological Diversity (CBD)

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526
Publications
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Introduction
Skills and Expertise

Publications

Publications (526)
Article
Background : Birch species such as Betula pendula have conspicuous white bark and the evolutionary drivers for this colouration remain unresolved. Aims We evaluated our hypothesis that the white bark is a visual warning signal to deter mammals from bark-stripping. Many species of deer (Cervidae) and multiple other mammals consume bark. White birch...
Article
Facultative endosymbionts can induce benefits and costs to their aphid hosts. In the pea aphid, Acyrthosiphon pisum (Harris) (Hemiptera: Aphididae), infection with the γ‐proteobacterium Hamiltonella defensa Moran et al. can confer resistance against parasitoids, but may also reduce the frequency of aggressive and escape behaviours exhibited in resp...
Article
Deimatic behaviours, also referred to as startle behaviours, are used against predators and rivals. Although many are spectacular, their proximate and ultimate causes remain unclear. In this review we aim to synthesise what is known about deimatic behaviour and identify knowledge gaps. We propose a working hypothesis for deimatic behaviour, and dis...
Article
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Background A broad range of scientific studies involve taking measurements on a circular, rather than linear, scale (often variables related to times or orientations). For linear measures there is a well-established statistical toolkit based on linear modelling to explore the associations between this focal variable and potentially several explanat...
Preprint
In a variety of aposematic species, the conspicuousness of an individual's warning signal and the quantity of its chemical defence are positively correlated. This apparent honest signalling in aposematism is predicted by resource competition models which assume that the production and maintenance of aposematic defences compete for access to antioxi...
Article
Spontaneous Magnetic Alignment (SMA), or the phenomenon by which animals orientate their bodies non-randomly with respect to a magnetic field, has been demonstrated in many taxa. While a 2013 study could only detect SMA in domestic dogs under calm magnetic field conditions, a more recent study has reported an extremely strong effect of magnetic ali...
Article
Full-text available
Many biological variables are recorded on a circular scale and therefore need different statistical treatment. A common question that is asked of such circular data involves comparison between two groups: Are the populations from which the two samples are drawn differently distributed around the circle? We compared 18 tests for such situations (by...
Article
A common situation in experimental science involves comparing a number of treatment groups each with a single reference (control group). For example, we might compare diameters of fungal colonies subject to a range of inhibitory agents with those from a control group to which no agent was applied. In this situation, the most commonly applied test i...
Preprint
Full-text available
A broad range of scientific studies involve taking measurements on a circular rather than linear scale (often times or orientations). For linear measures there is a well-established statistical toolkit based on linear modelling to explore the associations between this focal variable and potentially several explanatory factors and covariates. Howeve...
Article
Full-text available
Dropping behavior is an effective antipredator defense utilized by many insects including aphids, which drop from plants to lower plant parts or underlying substrates to avoid attack from predatory invertebrates. While research commonly focusses on triggers of dropping, less attention is given to what happens to prey individuals following escape dr...
Article
The many different islands of the Pacific provide a natural experiment that is ideal for studying predictors affecting plant cover and habitat-type. Previous research into pre-European deforestation and forest replacement across the Pacific islands detected multiple significant environmental and cultural variables. Here we re-analyse data for 67 is...
Article
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For herbivorous insects, dropping from the host plant is a commonly-observed antipredator defence. The use of dropping compared to other behaviours and its timing in relation to contact with a predator was explored in both pea aphids ( Acyrthosiphon pisum ) and potato aphids ( Macrosiphum euphorbiae ). Pea aphids dropped more frequently in response...
Preprint
Full-text available
Many biological variables, often involving timings of events or directions, are recorded on a circular rather than linear scale, and need different statistical treatment for that reason. A common question that is asked of such circular data involves comparison between two groups or treatments: Are the populations from which the two samples drawn di...
Article
Visual crypsis of prey is determined by the interaction between an individual’s physical appearance to their predators and visual aspects of their environment. Physical size will impact visual appearance and thus potentially influence crypsis. However, research on this topic is limited, leaving the effect of size in cryptic prey largely unexplored....
Article
Turn alternation is a locomotory behaviour wherein an animal makes consecutive turns in opposite directions (left-then-right or right-then-left). It has been suggested that its adaptive function is to maintain locomotion in a relatively constant general direction while negotiating obstacles. Previous work has focussed on the use of turn alternation...
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It is not uncommon for researchers to want to interrogate paired binomial data. For example, researchers may want to compare an organism’s response (positive or negative) to two different stimuli. If they apply both stimuli to a sample of individuals, it would be natural to present the data in a 2 × 2 table. There would be two cells with concordant...
Article
Full-text available
The most common statistical procedure with a sample of circular data is to test the null hypothesis that points are spread uniformly around the circle without a preferred direction. An array of tests for this has been developed. However, these tests were designed for continuously distributed data, whereas often (e.g. due to limited precision of mea...
Article
Full-text available
Many studies in biology involve data measured on a circular scale. Such data require different statistical treatment from those measured on linear scales. The most common statistical exploration of circular data involves testing the null hypothesis that the data show no aggregation and are instead uniformly distributed over the whole circle. The mo...
Article
Propensity scores are often used to adjust for between-group variation in covariates, when individuals cannot be randomized to groups. There is great flexibility in how these scores can be appropriately used. This flexibility might encourage p-value hacking – where several alternative uses of propensity scores are explored and the one yielding the...
Article
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Camouflage – adaptations that prevent detection and/or recognition – is a key example of evolution by natural selection, making it a primary focus in evolutionary ecology and animal behaviour. Most work has focused on camouflage as an anti‐predator adaptation. However, predators also display specific colours, patterns and behaviours that reduce vis...
Article
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Parent birds employ various strategies to protect their offspring against nest predators. Two well researched anti‐nest‐predation strategies involve visual concealment of the nest by way of parental camouflage and egg camouflage. By contrast, camouflage of nest structures is relatively under‐researched, particularly in the case of cup‐nests in tree...
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How foraging predators explore their environment is a fundamental aspect of predator-prey interactions. Girling et al. (2007) tested Coccinella septempunctata in a Y-maze, finding that approximately 45% of individuals displayed significant turning biases. We extend the work of Girling et al. in three ways: (1) turning bias was tested on vertical as...
Article
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Recent years have seen great interest in the suggestion that between-group aggression and within-group altruism have coevolved. However, these efforts have neglected the possibility that warfare – via its impact on demography – might influence human social behaviours more widely, not just those directly connected to success in war. Moreover, the po...
Article
O’Hara and Kotze (2010; Methods in Ecology and Evolution 1: 118‐122) present simulation results that appear to show very poor behaviour (as judged by bias and overall accuracy) of linear models (LMs) applied to count data, especially in relation to generalised linear model (GLM) analysis. We considered O’Hara and Kotze’s (2010) comparisons, and det...
Article
Distraction displays are conspicuous behaviours functioning to distract a predator's attention away from the displayer's nest or young, thereby reducing the chance of offspring being discovered and predated. Distraction is one of the riskier parental care tactics, as its success derives from the displaying parent becoming the focus of a predator's...
Article
The key selective pressure shaping the morphology of samaras is seen as enhancing primary wind‐borne dispersal from the parent plant to the ground. However, the consequences of the samara wing of primarily wind‐dispersed tree species for post‐dispersal processes has not been well studied. We explored whether the presence of this wing in Acer pseudo...
Article
40 years ago, the “life‐dinner principle” was proposed as an example of an asymmetry that may lead prey species to experience stronger selection than their predators, thus accounting for the high frequency with which prey escape alive from interaction with a predator. This principle remains an influential concept in the scientific literature, despi...
Article
Full-text available
Background: Circular data are gathered in diverse fields of science where measured traits are cyclical in nature: such as compass directions or times of day. The most common statistical question asked of a sample of circular data is whether the data seems to be drawn from a uniform distribution or one that is concentrated around one or more preferr...
Article
Winged seeds, or samaras, are believed to promote the long‐distance dispersal and invasive potential of wind‐dispersed trees, but the full dispersive potential of these seeds has not been well characterised. Previous research on the ecology of winged seeds has largely focussed on the initial abscission and primary dispersal of the samara, despite i...
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Background: For data collected on a circular rather than linear scale, a very common procedure is to test whether the underlying distribution appears to deviate from circular uniformity. Rao's spacing test is often used to evaluate the support the data offers for the null hypothesis of uniformity. Here we demonstrate that the traditional version o...
Article
Full-text available
The field of predator eavesdropping concentrates on the detection by a predator or parasite of signals that prey direct at conspecifics, and the subsequent evolution by prey to avoid or lessen such detection. Here, we first point out that signaling prey species are often found in mixed-species moving groups or stationary aggregations, and ask the q...
Article
Nguyen et al. (2016) offered advice to researchers in the commonly-encountered situation where they are interested in testing for a difference in central tendency between two populations. Their data and the available literature support very simple advice that strikes the best balance between ease of implementation, power and reliability. Specifical...
Article
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While several manipulated host behaviours are accepted as extended phenotypes of parasites, there remains debate over whether other altered behaviours in hosts following parasitic invasion represent cases of parasite manipulation, host defence or the pathology of infection. One particularly controversial subject is ‘suicidal behaviour’ in infected...
Chapter
Animals can use other prey species to learn about the presence of predators and reduce their risk of predation. Species living in the same area can eavesdrop on other species’ alarm signals or cues. Animals may also temporarily join other species to mob predators, or may associate more stably with other species in mixed-species groups, in which com...
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Pearson’s product moment correlation coefficient (more commonly Pearson’s r) tends to underestimate correlations that exist in the underlying population. This phenomenon is generally unappreciated in studies of ecology, although a range of corrections are suggested in the statistical literature. The use of Pearson’s r as the classical measure for c...
Article
Dropping is a common antipredator defence that enables rapid escape from a perceived threat. However, despite its immediate effectiveness in predator–prey encounters (and against other dangers such as a parasitoid or an aggressive conspecific), it remains an under‐appreciated defence strategy in the scientific literature. Dropping has been recorded...
Article
Full-text available
Interest in the evolutionary origins and drivers of warfare in ancient and contemporary small-scale human societies has greatly increased in the last decade, and has been particularly spurred by exciting archaeological discoveries that suggest our ancestors led more violent lives than previously documented. However, the striking observation that wa...
Book
Avoiding Attack discusses the diversity of mechanisms by which prey avoid predator attacks and explores how such defensive mechanisms have evolved through natural selection. It considers how potential prey avoid detection, how they make themselves unprofitable to attack, how they communicate this status, and how other species have exploited these s...
Article
Full-text available
Circular data are common in biological studies. The most fundamental question that can be asked of a sample of circular data is whether it suggests that the underlying population is uniformly distributed around the circle, or whether it is concentrated around at least one preferred direction (e.g. a migratory goal or activity phase). We compared th...
Article
Full-text available
Animal camouflage represents one of the most important ways of preventing (or facilitating) predation. It attracted the attention of the earliest evolutionary biologists, and today remains a focus of investigation in areas ranging from evolutionary ecology, animal decision-making, optimal strategies, visual psychology, computer science, to material...
Article
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Introduction Non-interventional and other observational studies have become important in medical research. In such observational, non-randomized studies, groups usually differ in some baseline covariates. Propensity scores are increasingly being used in the statistical analysis of these studies. Stratification, also called subclassification, based...
Article
Deflection occurs in predator-prey interactions where prey possess traits that influence the position of the predator's initial contact with the prey's body in a way that enhances the prey's probability of survival when attacked. As an anti-predatory defence occurring late in the sequence of an attack, deflection is an understudied but fascinating...
Article
Signals and cues are fundamental to social interactions. A well-established concept in the study of animal communication is an amplifier, defined as a trait that does not add extra information to that already present in the original cue or signal, but rather enhances the fidelity with which variation in the original cue or signal is correctly perce...
Article
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Insects are often chemically defended against predators. There is considerable evidence for a group-beneficial element to their defenses, and an associated potential for individuals to curtail their own investment in costly defense while benefitting from the investments of others, termed “automimicry.” Although females in chemically defended taxa o...
Article
Non-normality and heteroscedasticity are common in applications. For the comparison of two samples in the non-parametric Behrens–Fisher problem, different tests have been proposed, but no single test can be recommended for all situations. Here, we propose combining two tests, the Welch t test based on ranks and the Brunner–Munzel test, within a max...
Article
Full-text available
Thanatosis—also known as death-feigning and, we argue more appropriately, tonic immobility (TI)—is an under-reported but fascinating anti-predator strategy adopted by diverse prey late on in the predation sequence, and frequently following physical contact by the predator. TI is thought to inhibit further attack by predators and reduce the perceive...
Chapter
This chapter provides a discussion of roles in mixed-species groups (MSGs). Two such roles have been discussed extensively in the literature, leadership, and sentinel behavior. Leadership involves the ability to direct the movement of a group. Several ways to define leadership are discussed including qualitative and quantitative assessments. Partic...
Chapter
This chapter summarizes what is known about the conservation implications of mixed-species grouping and mixed-species associations more generally. Using mostly data on mixed-species bird flocks, the text highlights how groups generally diminish in size and frequency outside forests, and reviews what is, and is not, known about the cause of these oc...
Chapter
This is the first of two linked chapters that focus particularly on fitness consequences of mixed-species grouping. This chapter focuses on fitness implications through mechanisms other than avoiding predation—and these involve exploitation of food or other environmental resources; coping with the physical challenges of interaction with the environ...
Chapter
This chapter is the companion to the previous one, and focuses on the consequences of mixed-species association (MSA) for risk of attack from antagonists such as predators and parasites. We begin by considering how established mechanisms for grouping influencing predation risk are affected by mixed-species group (MSG) composition. We then explore h...
Chapter
This chapter builds on the previous one by now focusing on moving mixed-species groups (MSGs) or aggregations, and summarizing what kinds of animals have been described to participate in them. The chapter starts with invertebrates, rarely described in MSGs, and then progresses through fish and mammals, to birds, which are the taxa most frequently f...
Chapter
This chapter synthesizes what the authors learned while writing the book and where research priorities now lie. New empirical directions include understanding the dominance of birds in mixed-species associations, increasing our knowledge on invertebrates, and using citizen science to gather new data. From the theoretical perspective, the chapter ar...
Chapter
This chapter provides a description of the various types of cues and signals used in mixed-species groups. The simplest form of communication involves eavesdropping on cues and signals produced by other species. This can be helpful to locate resources and groups, mob predators, and assess predation risk. Signals, by contrast, are produced so as to...
Chapter
This chapter, investigates the wide variety of mixed-species associations among animals, by focusing on association types that do not make the “interaction” or the “moving” criteria of our mixed-species group definition. Different kinds of aggregations are summarized, including those in habitat patches or those formed around food resources or preda...
Article
Pseudoreplication is controversial across experimental biology. Researchers in the same field can disagree on whether a given study suffers from pseudoreplication and on to what extent any pseudoreplication undermines the value of a study. A recent survey indicated that concerns about pseudoreplication can strongly impact peer review of manuscripts...
Article
Full-text available
Limits to the precision of circular data often cause grouping of data points into discrete categories, but the effects of grouping on tests for circular uniformity have been little explored. The Rayleigh test is often applied to grouped circular data, despite it being designed for continuous data and the statistical literature recommending a suite...
Article
Many diverse hypotheses have been suggested for the stripes of the plains zebra Equus quagga. We propose a new hypothesis that this adaptation represents visual interspecies signalling to facilitate mixed-species herding. Mixed-species herds likely offer enhanced protection from predation. They can also facilitate feeding for both zebra and other g...
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This review offers the first synthesis of the research on mixed-species groupings of arthropods and highlights the behavioural and evolutionary questions raised by such behaviour. Mixed-species groups are commonly found in mammals and birds. Such groups are also observed in a large range of arthropod taxa independent of their level of sociality. Se...
Book
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Mixed-Species Groups of Animals: Behavior, Community Structure, and Conservation highlights a spectacular and accessible example of the complexity of species interactions. The work first surveys the diversity of spatial associations among animals, then concentrates on moving groups. The authors review the major theories that have been developed to...
Article
A common approach to the analysis of experimental data across much of the biological sciences is test-qualified pooling. Here non-significant terms are dropped from a statistical model, effectively pooling the variation associated with each removed term with the error term used to test hypotheses (or estimate effect sizes). This pooling is only car...
Article
Full-text available
Recent years have seen an explosion of multidisciplinary interest in ancient human warfare. Theory has emphasized a key role for kin-selected cooperation, modulated by sex-specific demography, in explaining intergroup violence. However, conflicts of interest remain a relatively underexplored factor in the evolutionary-ecological study of warfare, w...
Article
In experiments where subjects are allocated to different treatments, implementing allocation concealment simply means that procedures are used to prevent conscious or unconscious human bias influencing the allocation of particular subjects to particular treatments. It is a related, but distinct, procedure to blinding. Allocation concealment is a ne...
Article
Full-text available
Prey animals that possess chemical defences often advertise their unprofitability to predators by a distinctive and conspicuous visual appearance known as aposematism. However, not all chemically defended species are conspicuous, and some are nearly cryptic. Differences in predator community composition and predator behaviour may explain varied lev...
Article
Full-text available
Prey animals that possess chemical defences often advertise their unprofitability to predators by a distinctive and conspicuous visual appearance known as aposematism. However, not all chemically defended species are conspicuous, and some are nearly cryptic. Differences in predator community composition and predator behaviour may explain varied lev...
Article
Persons and Currie (2015) argued against either flight, thermoregulation, or signalling as a functional benefit driving the earliest evolution of feathers; rather, they favoured simple feathers having an initial tactile sensory function, which changed to a thermoregulatory function as density increased. Here, we explore the relative merits of early...
Article
Full-text available
Prey often evolve defences to deter predators, such as noxious chemicals including toxins. Toxic species often advertise their defence to potential predators by distinctive sensory signals. Predators learn to associate toxicity with the signals of these so-called aposematic prey, and may avoid them in future. In turn, this selects for mildly toxic...
Data
Complete description of the model implementation. (DOCX)
Article
Although circular data are common in biological studies, the analysis of such data is often more rudimentary than it need be. One of the most common hypotheses tested is whether the data suggest that samples are clustered around a certain specified direction, rather than being uniformly spread across all possible directions. Here, I use data from a...
Article
Countershading, the widespread tendency of animals to be darker on the side that receives strongest illumination, has classically been explained as an adaptation for camouflage: obliterating cues to 3D shape and enhancing background matching. However, there have only been two quantitative tests of whether the patterns observed in different species...