Christos C Ioannou

Christos C Ioannou
University of Bristol | UB · School of Biological Sciences

PhD

About

134
Publications
20,404
Reads
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4,152
Citations
Additional affiliations
October 2013 - present
University of Bristol
Position
  • NERC Independent Research Fellow

Publications

Publications (134)
Article
Full-text available
Although numerous influential models in ecology assume a directly proportional relationship between prey density and prey encounter rate, a recent test of this assumption found that the actual relationship was nonlinear (rising slower than proportionately). Here, three-spined sticklebacks were used to test 2 recently proposed mechanisms based on pr...
Chapter
Full-text available
IntroductionCollective motionEmergent collective motion in the absence of external stimuliResponse to internal state and external stimuli: Information processing within schoolsInformational status, leadership and collective decision-making in fish schoolsThe structure of fish schools and populationsSocial networks and individual identitiesCommunity...
Article
Full-text available
Larger groups often have a greater ability to solve cognitive tasks compared to smaller ones or lone individuals. This is well established in social insects, navigating flocks of birds, and in groups of prey collectively vigilant for predators. Research in social insects has convincingly shown that improved cognitive performance can arise from self...
Article
Full-text available
Marginal predation, also known as the edge effect, occurs when aggregations of prey are preferentially targeted on their periphery by predators and has long been established in many taxa. Two main processes have been used to explain this phenomenon, the confusion effect and the encounter rate between predators and prey group edges. However, it is u...
Article
Full-text available
Although consistent behavioural differences between individuals (i.e. personality variation) are now well established in animals, these differences are not always expressed when individuals interact in social groups. This can be key in important social dynamics such as leadership, which is often positively related to personality traits such as bold...
Article
Full-text available
Significance A widespread strategy used by prey animals, seen in insects, mammals, amphibians, crustaceans, fish, and reptiles, is to vary the direction in which they escape when attacked by a predator. This unpredictability is thought to benefit prey by inhibiting predators from predicting the prey’s escape trajectory, but experimental evidence is...
Article
Chemical pollution is among the fastest-growing agents of global change. Synthetic chemicals with diverse modes-of-action are being detected in the tissues of wildlife and pervade entire food webs. Although such pollutants can elicit a range of sublethal effects on individual organisms, research on how chemical pollutants affect animal groups is se...
Preprint
Full-text available
The movement of groups can be heavily influenced by 'leader' individuals who differ from the others in some way. A major source of differences between individuals is the repeatability and consistency of their behaviour, commonly considered as their 'personality', which can influence both position within a group as well as the tendency to lead. Howe...
Article
Full-text available
During the early stage of biological invasions, interactions occur between native and non-native species that do not share an evolutionary history. This can result in ecological naïveté, causing native species to exhibit maladaptive behavioural responses to novel enemies, leading to negative consequences for individual fitness and ecosystem functio...
Article
Full-text available
Invasive species cause substantial changes to the biodiversity of freshwater systems. The African Nile tilapia (Oreochromis niloticus) is now widely distributed in tropical freshwaters globally. Despite indications that feral populations can influence native species through competitive effects, direct evidence of competition between Nile tilapia an...
Article
A new study on fish shows that the patterns collective animal groups display when they are disturbed can dissuade predators from attacking.
Article
Full-text available
Despite the potential benefits gained from behavioural lateralisation, defined as the asymmetrical expression of cognitive functioning, this trait demonstrates widespread variation within and between populations. Numerous methodologies have been applied to investigate lateralisation, although whether different methodologies give consistent results...
Article
Full-text available
Within animal populations there is variation among individuals in their tendency to be social, where more sociable individuals associate more with other individuals. Consistent inter-individual variation in ‘sociability’ is considered one of the major axes of personality variation in animals along with aggressiveness, activity, exploration and bold...
Article
Full-text available
As individual animals are exposed to varying environmental conditions, phenotypic plasticity will occur in a vast array of physiological traits. For example, shifts in factors such as temperature and oxygen availability can affect the energy demand, cardiovascular system, and neuromuscular function of animals that in turn impact individual behavior...
Article
Full-text available
Despite extensive interest in the dynamic interactions between individuals that drive collective motion in animal groups, the dynamics of collective motion over longer time frames are understudied. Using three-spined sticklebacks, Gasterosteus aculeatus, randomly assigned to 12 shoals of eight fish, we tested how six key traits of collective motion...
Article
Full-text available
Both empirical and theoretical studies show that an individual's spatial position within a group can impact the risk of being targeted by predators. Spatial positions can be quantified in numerous ways, but there are no direct comparisons of different spatial measures in predicting the risk of being targeted by real predators. Here, we assess these...
Article
Full-text available
Invasive species are one of the greatest threats to freshwater ecosystems globally. However, the causal mechanisms that drive negative impacts of many invasive species are poorly understood. In Tanzania, non-native Nile tilapia (Oreochromis niloticus) exists in sympatry with a diverse range of native species, many of which are congenerics with stro...
Preprint
Full-text available
As individual animals are exposed to varying environmental conditions, phenotypic plasticity will occur in a vast array of physiological traits. For example, shifts in factors such as temperature and oxygen availability can affect the energy demand, cardiovascular system, and neuromuscular function of animals that in turn impact individual behaviou...
Preprint
Full-text available
Both empirical and theoretical studies show that an individual's spatial position within a group can impact the risk of being targeted by predators. Spatial positions can be quantified in numerous ways, but there are no direct comparisons of different spatial measures in predicting the risk of being targeted by real predators. Here we assess these...
Article
The environment contains different forms of ecological noise that can reduce the ability of animals to detect information. Here, we ask whether animals adapt their behavior to either exploit or avoid areas of their environment with increased dynamic visual noise. Three-spined sticklebacks (Gasterosteus aculeatus) were immersed in environments with...
Preprint
Full-text available
To increase their chances of survival, prey often respond to predators by being unpredictable when escaping, but the response of predators to such tactics is unknown. We programmed interactive robot-controlled prey to flee from an approaching blue acara predator (Andinoacara pulcher), allowing us to manipulate the predictability of the prey's initi...
Article
Full-text available
Consistent inter-individual variation in behaviour within a population, widely referred to as personality variation, can be affected by environmental context. Feedbacks between an individual’s behaviour and state can strengthen (positive feedback) or weaken (negative feedback) individual differences when experiences such as predator encounters or w...
Article
Full-text available
Anthropogenic activity can increase water turbidity, changing fish behaviour by reducing visibility. The spread of invasive species is also facilitated by human activity, further increasing the pressure on native species. In two experiments, we measured the foraging efficiency, risk perception and inter-individual consistency of risk-taking (person...
Preprint
Full-text available
Despite extensive interest in the dynamic interactions between individuals that drive collective motion in animal groups, the dynamics of collective motion over longer time frames are understudied. Using three-spined sticklebacks, Gasterosteus aculateus, randomly assigned to twelve shoals of eight fish, we tested how six key traits of collective mo...
Article
Full-text available
Consistent interindividual differences in behaviour (i.e. animal personality variation) can influence a range of ecological and evolutionary processes, including predation. Variation between individual predators in commonly measured personality traits, such as boldness and activity, has previously been linked to encounter rates with their prey. Giv...
Article
Full-text available
While larger groups tend to be better at making decisions, very few studies have explored how ecological variables, including predation pressure, shape how group size affects decision making. Our cross-population study of wild-caught guppies ( Poecilia reticulata ) shows that leading individuals from larger groups made faster decisions when decidin...
Article
Full-text available
Collective movement is critical to the survival of some animals. Despite substantial progress in understanding animal collectives such as fish shoals and bird flocks, it is unknown how collective behaviour is affected by changes in multiple environmental conditions that can interact as stressors. Using a fully factorial repeated-measures design, we...
Preprint
The environment contains different forms of ecological noise that can reduce the ability of animals to detect information. Here we ask whether animals can adapt their behaviour to either exploit or avoid areas of their environment with increased dynamic visual noise. By immersing three-spined sticklebacks ( Gasterosteus aculeatus ) into environment...
Preprint
Full-text available
Accurate assessment of the health status of individual animals is a key step in timely and targeted treatment of infections, which is critical in the fight against anthelmintic and antimicrobial resistance. The FAMACHA scoring system has been used successfully to detect levels of anaemia caused by infection with the parasitic nematode Haemonchus co...
Preprint
Full-text available
Anthropogenic activity can increase water turbidity, changing fish behaviour by reducing visibility. The spread of invasive species is also facilitated by human activity, further increasing the pressure on native species. In two experiments we measured the foraging efficiency, risk perception and inter-individual consistency of risk-taking (persona...
Preprint
Full-text available
Consistent inter-individual variation within a population, widely referred to as personality variation, can be affected by environmental context. Feedbacks between an individual's personality and state can strengthen (positive feedback) or weaken (negative feedback) individual differences when experiences such as predator encounters or winning cont...
Preprint
Consistent inter-individual differences in behaviour (i.e. animal personality variation) can influence a range of ecological and evolutionary processes, including predation. Variation between individual predators in commonly measured personality traits, such as boldness and activity, has previously been linked to encounter rates with their prey. Gi...
Article
Full-text available
Limited attention constrains predators from engaging in cognitively demanding tasks such as searching for cryptic prey at the same time as remaining vigilant towards threats. Since finite attention can result in negative correlations between foraging and vigilance, the tendency of individual predators to focus attention on searching for cryptic pre...
Article
Full-text available
Animal groups vary in their collective order (or state), forming disordered swarms to highly polarized groups. One explanation for this variation is that individuals face differential benefits or costs depending on the group’s order, but empirical evidence for this is lacking. Here we show that in three-spined sticklebacks (Gasterosteus aculeatus),...
Article
Full-text available
A fundamental question in animal ecology is how an individual's internal state and the external environment together shape species distributions across habitats. The increasing availability of biologgers is driving a revolution in answering this question in a wide range of species. In this study, the position of sheep (Ovis aries) from Global Posit...
Article
Full-text available
Collective decision-making is predicted to be more egalitarian in conditions where the costs of group fission are higher. Here, we ask whether Trinidadian guppies (Poecilia reticulata) living in high or low predation environments, and thereby facing differential group fission costs, make collective decisions in line with this prediction. Using a cl...
Article
Full-text available
Detailed quantifications of how predators and their grouping prey interact in three dimensions (3D) remain rare. Here we record the structure and dynamics of fish shoals (Pseudomugil signifer) in 3D both with and without live predators (Philypnodon grandiceps) under controlled laboratory conditions. Shoals adopted two distinct types of shoal struct...
Article
Full-text available
Turbidity reduces the distance that animals can detect food, predators and conspecifics. How turbidity affects decision making in social contexts has rarely been investigated; moreover, it is unknown whether decreased shoaling in turbid water is due to visual constraints (a mechanistic explanation) or a reduced perception of predation risk (an adap...
Article
Full-text available
A long-standing assumption in social behavior is that leadership incurs costs as well as benefits, and this tradeoff can result in diversified social roles in groups. The major cost of leadership in moving animal groups is assumed to be predation, with individuals leading from the front of groups being targeted more often by predators. Nevertheless...
Article
Full-text available
Mutualistic interactions involve 2 species beneficially cooperating, but it is not clear how these interactions are maintained. In many mutualisms, one species interacts with multiple species, and since partners differ in terms of the commodities they trade, partner identity will directly influence the decisions and behaviors of interacting individ...
Article
Full-text available
Mated pair bonds are integral to many animal societies, yet how individual variation in behaviour influences their formation remains largely unknown. In a population of wild great tits (Parus major), we show that personality shapes pair bonding: proactive males formed stronger pre-breeding pair bonds by meeting their future partners sooner and incr...
Article
Full-text available
How effective groups are in making decisions is a long-standing question in studying human and animal behaviour. Despite the limited social and cognitive abilities of younger people, skills which are often required for collective intelligence, studies of group performance have been limited to adults. Using a simple task of estimating the number of...
Data
The relationship between individual estimates before and after group discussion in Experiment 1. (PDF)
Data
The effect of disagreement (range) in initial estimates on improving group estimates in Experiment 2. (PDF)
Data
The effect of question order and treatment on the disagreement (range) of initial estimates in Experiment 2. (PDF)
Data
Summary of statistical tests in Experiment 1. (PDF)
Data
Summary of statistical tests from Experiment 2. (PDF)
Data
Data from Experiment 1 (.csv format). (CSV)
Data
Log-likelihood of simple aggregation rules, the noisy geometric mean model, and confidence intervals for frequencies of the aggregation rules using the noisy geometric mean model. (PDF)
Data
The relationship between the range of initial estimates and estimates given by the group or calculated from initial estimates in Experiment 1. (PDF)
Data
Fits of different aggregation rules to the observed data at various levels of added noise in Experiment 1. (PDF)
Data
Distribution of individual initial estimates in Experiment 2. (PDF)
Data
The effect of question order on the absolute error of (initial and group consensus) estimates in Experiment 2. (PDF)
Data
The age distribution of participants in Experiment 1, correlations within groups, and distribution of individual initial estimates. (PDF)
Data
The jars of sweets used in Experiment 1 and Experiment 2. (PDF)
Data
The use and consequence of different aggregation rules for different thresholds that define groups as having a low or high range in Experiment 1. (PDF)
Data
Correlations across treatments in the range of individual initial estimates per group. (PDF)
Data
The relationship between participants’ self-rated confidence and error and the change in individuals estimates between stages. (PDF)
Data
Absolute error of the geometric rule compared to the other aggregation rules and the observed consensus estimates (Experiment 1), for all groups, and then with the groups split by those with low (≤40) and high ranges (>40). (PDF)
Data
Data from Experiment 2 (.csv format). (CSV)
Data
The distribution of the difference between the group estimate and the mean of initial estimates. (PDF)