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To overcome the cost of competition resulting from close social proximity while foraging in a group, individuals may balance their use of private (i.e. acquired from personal sampling) and social (i.e. acquired by watching other individuals) information in order to adjust their foraging strategy accordingly. Reliability of private information about environmental characteristics, such as the spatial distribution of prey, is thus likely to affect individual movement and social interactions during foraging. Our aim was to investigate how movement characteristics of foraging individuals changed as they acquired reliable private information about the spatial occurrence of prey in a foraging context. We allowed guppies (Poecilia reticulata) to develop the reliability of their private knowledge about prey spatial occurrence by repeatedly testing shoals in a foraging task under three experimental distributions of prey: 1) aggregated prey forming three patches located in fixed locations, 2) scattered distribution of prey with random locations, or 3) no prey (used as control). We then applied tracking methods to obtain individual time series of spatial coordinates from which we computed a suite of movement variables reflecting search effort, social proximity and locomotion characteristics during foraging, in order to examine changes occurring over repeated trials and to investigate which best explained foraging success. We show that foraging shoals became more efficient at finding and consuming food over the first three days by increasing their time spent active. Over time, individuals foraging on either scattered or aggregated prey travelled greater distances, showed an increasing distance to their closest neighbour and became slightly more stochastic in their acceleration profile, compared to control individuals. We found that behaviour changed as private information increased over time. Social proximity was the major predictor of foraging success in the absence of prior foraging information, while stochasticity in acceleration and search effort became the most important predictors of foraging success as information increased. In conclusion, we show that individual movement patterns changed as they acquire private information. Contrary to our predictions, the spatial distribution of prey did not affect any of the movement variables of interest. Our results emphasise the importance of information, both private and social, in shaping movement behaviour in animals. Keywords: social foraging, movement, private information, prey spatial distribution, fish.

SummaryPredation is one of the main evolutionary drivers of social grouping. While it is well appreciated that predation risk is likely not shared equally among individuals within groups, its detailed quantification has remained difficult due to the speed of attacks and the highly-dynamic nature of collective prey response. Here, using high-resolution tracking of solitary predators (Northern pike) hunting schooling fish (golden shiners), we not only provide detailed insights into predator decision-making but show which key spatial and kinematic features of predator and prey influence individual’s risk to be targeted and survive attacks. Pike tended to stealthily approach the largest groups, and were often already inside the school when launching their attack, making prey in this frontal “strike zone” the most vulnerable to be targeted. From the prey’s perspective, those fish in central locations, but relatively far from, and less aligned with, neighbours, were most likely to be targeted. While the majority of attacks (70%) were successful, targeted individuals that did manage to avoid capture exhibited a higher maximum acceleration response just before the attack and were further away from the pike‘s head. Our results highlight the crucial interplay between predators’ attack strategy and response of prey in determining predation risk in mobile animal groups.

Predation is one of the main drivers of animal grouping. However, predation risk is not shared equally within groups. Despite long-standing theoretical work and strong empirical insights, very little work has examined the real-time dynamics of predators attacking groups of prey nor quantified the features that predict prey predation risk and survival. Here we used high resolution tracking of Northern pike (Esox lucius) attacking large schools of prey (golden shiner fish, Notemigonus crysoleucas) to get a mechanistic quantification of predation at every stage of the attack. We found that pike tended to attack the groups head-on, but did so stealthily, often striking only when partly within the school. From the predator’s perspective, relative position to the prey was the most important feature, with shiners very close and directly in front of the pike being most at risk. From the prey’s perspective, we found that central individuals, with relatively low local neighbour density and alignment, face increased risk. While the majority of attacks were successful, escape was associated with individuals achieving high maximum movement speeds, relative to others. Our study highlights both predator attack strategy and prey behaviour are key factors underlying the predation risk of grouping prey, and our results contradict the long-held assertion arising from Hamilton’s “selfish herd” concept that central positions are safer. To ultimately understand the cost-benefits that underly the evolution of animal grouping it is thus key to consider the multifaceted, and dynamical, nature of predator-prey relationships.

Food availability and temperature influence energetics of animals and can alter behavioral responses such as foraging and spontaneous activity. Food availability, however, is not necessarily a good indicator of energy (ATP) available for cellular processes. The efficiency of energy transduction from food‐derived substrate to ATP in mitochondria can change with environmental context. Our aim was to determine whether the interaction between food availability and temperature affects mitochondrial efficiency and behavior in zebrafish (Danio rerio). We conducted a fully factorial experiment to test the effects of feeding frequency, acclimation temperature (three weeks to 18 or 28°C), and acute test temperature (18 and 28°C) on whole‐animal oxygen consumption, mitochondrial bioenergetics and efficiency (ADP consumed per oxygen atom; P:O ratio), and behavior (boldness and exploration). We show that infrequently fed (once per day on four days per week) zebrafish have greater mitochondrial efficiency than frequently fed (three times per day on five days per week) animals, particularly when warm‐acclimated. The interaction between temperature and feeding frequency influenced exploration of a novel environment, but not boldness. Both resting rate of producing ATP and scope for increasing it were positively correlated with time spent exploring and distance moved in standardized trials. In contrast, behavior was not associated with whole‐animal aerobic (oxygen consumption) scope, but exploration was positively correlated with resting oxygen consumption rates. We highlight the importance of variation in both metabolic (oxygen consumption) rate and efficiency of producing ATP in determining animal performance and behavior. Oxygen consumption represents energy use, and P:O ratio is a variable that determines how much of that energy is allocated to ATP production. Our results emphasize the need to integrate whole‐animal responses with subcellular traits to evaluate the impact of environmental conditions on behavior and movement., Food availability and temperature influence energetics of animals and can alter behavioral responses. We show that infrequently fed zebrafish have greater mitochondrial efficiency than frequently fed animals, particularly when warm‐acclimated. The interaction between temperature and feeding frequency influenced exploration of a novel environment, but not boldness.

Parasitism is ubiquitous in the animal kingdom. Although many fundamental aspects of host-parasite relationships have been unravelled, few studies have systematically investigated how parasites affect organismal movement. Here we combine behavioural experiments ofSchistocephalus solidusinfected sticklebacks with individual-based simulations to understand how parasitism affects individual movement ability and how this in turn influences social interaction patterns. Detailed movement tracking revealed that infected fish swam slower, accelerated slower, turned more slowly, and tended to be more predictable in their movements than did non-infected fish. Importantly, the strength of these effects increased with increasing parasite load (% of body weight), with the behaviour of more heavily infected fish being more impaired. When grouped, pairs of infected fish moved more slowly, were less cohesive, less aligned, and less coordinated than healthy pairs. Mixed pairs exhibited intermediate behaviours and were primarily led by the non-infected fish. These social patterns emerged naturally in model simulations of self-organised groups composed of individuals with different speeds and turning tendency, consistent with changes in mobility and manoeuvrability due to infection. Together, our results demonstrate how infection with a complex life cycle parasite affects the movement ability of individuals and how this in turn shapes social interactions, providing important mechanistic insights into the effects of parasites on host movement dynamics.

9 pages; International audience; In recent years, considerable research interest in behavioral ecology has focused on characterizing and understanding individual differences in behavior that are consistent over time and across contexts, termed animal “personalities,” and correlations between various behaviors across contexts, termed behavioral syndromes. Although there is some evidence that differences in personality among individuals within populations can be genetically based and adaptive, when and how individual personality differences emerge in a population is not well understood, but of considerable general interest. Here, using juveniles of the convict cichlid (Amatitlania siquia) as a model system, we investigated in the laboratory whether individuals consistently differ in their personalities and whether behavioral syndromes are apparent at an early developmental stage and, if so, whether distinct personality traits are heritable. Under standardized laboratory conditions and using sibling analysis, we quantified interindividual differences in their boldness behavior under potential predation threat and their exploratory activity in a novel environment, 2 ecologically important behaviors, as our focal personality traits and estimated their respective repeatability and heritability. We report for the first time consistent (repeatable) and heritable individual differences in boldness and exploratory behaviors, and a boldness–exploration behavioral syndrome, in young convict cichlids. Bolder fish were more exploratory than relatively timid ones. These results provide novel evidence for the emergence in early life history of consistent individual differences in personality traits and behavioral syndromes in this species and suggest that genetic variation for boldness and exploratory behaviors, and thus potential for selection on these traits, exists in our study population.