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Cooperative breeding is widely reported across the animal kingdom. In birds, it is hypothesised to be most common in altricial species (where chicks are dependent on parental care in the nest after hatching), with few described cases in precocial species (where chicks are more independent immediately after hatching). However, cooperative breeding may also be more difficult to detect in precocial species and therefore has been overlooked. In this study, we investigate whether vulturine guineafowl (Acryllium vulturinum)—which have precocial young—breed cooperatively and, if so, how care is distributed among group members. Using data collected from colour-banded individuals in one social group of vulturine guineafowl over three different breeding seasons, we found that multiple females can attempt to reproduce in the same breeding season. Broods had close adult associates, and most of these associates exhibited four distinct cooperative breeding behaviours: babysitting, within-group chick guarding, covering the chicks under the wings and calling the chicks to food. Further, we found that offspring care is significantly male-biased, that non-mother individuals provided most of the care each brood received, that breeding females differed in how much help they received, and that carers pay a foraging cost when providing care. Our results confirm that vulturine guineafowl are cooperative breeders, which they combine with an unusual plural-breeding social system. Our study also adds to growing evidence that cooperative breeding may be more widespread among species with precocial young than previously thought, thereby providing a counterpoint to the altriciality-cooperative breeding hypothesis.

GPS-based tracking is widely used for studying wild social animals. Much like traditional observational methods, using GPS devices requires making a number of decisions about sampling that can affect the robustness of a study’s conclusions. For example, sampling fewer individuals per group across more distinct social groups may not be sufficient to infer group- or subgroup-level behaviours, while sampling more individuals per group across fewer groups limits the ability to draw conclusions about populations. Here, we provide quantitative recommendations when designing GPS-based tracking studies of animal societies. We focus on the trade-offs between three fundamental axes of sampling effort: 1) sampling coverage—the number and allocation of GPS devices among individuals in one or more social groups; 2) sampling duration—the total amount of time over which devices collect data; 3) sampling frequency—the temporal resolution at which GPS devices record data. We first test GPS tags under field conditions to quantify how these aspects of sampling design can affect both GPS accuracy (error in absolute positional estimates) and GPS precision (error in the estimate relative position of two individuals), demonstrating that GPS error can have profound effects when inferring distances between individuals. We then use data from whole-group tracked vulturine guineafowl (Acryllium vulturinum) to demonstrate how the trade-off between sampling frequency and sampling duration can impact inferences of social interactions and to quantify how sampling coverage can affect common measures of social behaviour in animal groups, identifying which types of measures are more or less robust to lower coverage of individuals. Finally, we use data-informed simulations to extend insights across groups of different sizes and cohesiveness. Based on our results, we are able to offer a range of recommendations on GPS sampling strategies to address research questions across social organizational scales and social systems—from group movement to social network structure and collective decision-making. Our study provides practical advice for empiricists to navigate their decision-making processes when designing GPS-based field studies of animal social behaviours, and highlights the importance of identifying the optimal deployment decisions for drawing informative and robust conclusions.

Dominance is important for access to resources. As dominance interactions are costly, individuals should be strategic in whom they interact with. One hypothesis is that individuals should direct costly interactions towards those closest in rank, as they have most to gain—in terms of attaining or maintaining dominance—from winning such interactions. Here, we show that male vulturine guineafowl (Acryllium vulturinum), a gregarious species with steep dominance hierarchies, strategically express higher-cost aggressive interactions towards males occupying ranks immediately below themselves in their group's hierarchy. By contrast, lower-cost aggressive interactions are expressed towards group members further down the hierarchy. By directly evaluating differences in the strategic use of higher- and lower-cost aggressive interactions towards competitors, we show that individuals disproportionately use highest-cost interactions—such as chases—towards males found one to three ranks below themselves. Our results support the hypothesis that the costs associated with different interaction types can determine their expression in social groups with steep dominance hierarchies.This article is part of the theme issue ‘The centennial of the pecking order: current state and future prospects for the study of dominance hierarchies’.

Dominance is important for access to resources. As dominance interactions are costly, individuals should be strategic in who they interact with. One hypothesis is that individuals should direct costly interactions towards those closest in rank, as they have most to gain--in terms of attaining or maintaining dominance--from winning such interactions. Here, we develop a novel analytical framework to test whether interactions are directed strategically in relation to rank differences, and use these to compare strategies across types of interactions that vary in cost. We show that male vulturine guineafowl (Acryllium vulturinum), a gregarious species with steep dominance hierarchies, strategically direct costly interactions towards males occupying ranks immediately below themselves in their group9s hierarchy. In contrast, low-cost interactions are not directed towards closest competitors, but towards group members slightly further down the hierarchy. We then show that, as a result of the difference in strategic use of high- and low-cost interactions towards closest competitors, individuals disproportionately use highest-cost interactions--such as chases--towards males found one to three ranks below them. Our results support the hypothesis that the costs associated with different interaction types can determine their expression in social groups.

1. The social decisions that individuals make—who to interact with and how frequently—gives rise to social structure. The resulting social structure then determines how individuals interact with their surroundings—resources and risks, pathogens and predators, competitors and cooperators. 2. However, despite intensive research on (i) how individuals make social decisions and (ii) how social structure shapes social processes (e.g. cooperation, competition and conflict), there are still few studies linking these two perspectives. These perspectives represent two halves of a feedback loop: individual behaviour scales up to define the social environment, and this environment, in turn, feeds back by shaping the selective agents that drive individual behaviour. 3. We first review well-established research areas that have captured both elements of this feedback loop—host-pathogen dynamics and cultural transmission. We then highlight areas where social structure is well studied but the two perspectives remain largely disconnected. Finally, we synthesise existing research on 14 distinct research topics to identify new prospects where the interplay between social structure and social processes are likely to be important but remain largely unexplored. 4. Our review shows that the inherent links between individuals’ traits, their social decisions, social structure, and social evolution, warrant more consideration. By mapping the existing and missing connections among many research areas, our review highlights where explicitly considering social structure and the individual-to-society feedbacks can reveal new dimensions to old questions in ecology and evolution.

Animal societies can be organised in multiple hierarchical tiers [1]. Such multilevel societies, where stable groups move together through the landscape, overlapping and associating preferentially with specific other groups, are thought to represent one of the most complex forms of social structure in vertebrates. For example, hamadryas baboons (Papio hamadryas) live in units consisting of one male and one or several females, or of several solitary males, that group into clans. These clans then come together with solitary bachelor males to form larger bands [2]. This social structure means that individuals have to track many different types of relationships at the same time [1,3]. Here, we provide detailed quantitative evidence for the presence of a multilevel society in a small-brained bird, the vulturine guineafowl (Acryllium vulturinum). We demonstrate that this species lives in large, multi-male, multi-female groups that associate preferentially with specific other groups, both during the day and at night-time communal roosts.

Collective decision-making is a daily occurrence in the lives of many group-living animals, and can have critical consequences for the fitness of individuals. Understanding how decisions are reached, including who has influence and the mechanisms by which information and preferences are integrated, has posed a fundamental challenge. Here, we provide a methodological framework for studying influence and leadership in groups. We propose that individuals have influence if their actions result in some behavioural change among their group-mates, and are leaders if they consistently influence others. We highlight three components of influence (influence instances, total influence and consistency of influence), which can be assessed at two levels (individual-to-individual and individual-to-group). We then review different methods, ranging from individual positioning within groups to information-theoretic approaches, by which influence has been operationally defined in empirical studies, as well as how such observations can be aggregated to give insight into the underlying decision-making process. We focus on the domain of collective movement, with a particular emphasis on methods that have recently been, or are being, developed to take advantage of simultaneous tracking data. We aim to provide a resource bringing together methodological tools currently available for studying leadership in moving animal groups, as well as to discuss the limitations of current methodologies and suggest productive avenues for future research. This article is part of the theme issue ‘Collective movement ecology’.

Every spring a huge number of passerines cross the Sahara Desert and the Mediterranean Sea on their way to their breeding grounds. Stopover sites after such extended barriers where birds can rest, refuel, and find shelter from adverse weather, are of crucial importance for the outcome of their migration. Stopover habitat selection used by migrating birds depends on landscape context, habitat patch characteristics, as well as on the particular energetic conditions and needs of individual birds, but it is still poorly investigated. We focused on a long-distance migrating passerine, the woodchat shrike, in order to investigate for the first time the species’ habitat selection at a spring stopover site (island of Antikythira, Greece) after the crossing of the Sahara Desert and Mediterranean Sea. We implemented radio-tracking, color-ringing, and visual behavioral observations to collect data on microhabitat use. Generalized Linear Mixed Models were developed to identify the species’ most preferred microhabitat during its stopover on this low human disturbed island. We found that high maquis vegetation surrounded by low vegetation was chosen as perches for hunting. Moreover, high maquis vegetation appeared to facilitate hunting attempts toward the ground, the most frequently observed foraging strategy. Finally, we discuss our findings in the context of conservation practices for the woodchat shrike and their stopover sites on Mediterranean islands.

Every spring a huge number of passerines cross the Sahara Desert and the Mediterranean Sea on their way to their breeding grounds. Stopover sites after such extended barriers where birds can rest, refuel, and find shelter from adverse weather, are of crucial importance for the outcome of their migration. Stopover habitat selection used by migrating birds depends on landscape context, habitat patch characteristics, as well as on the particular energetic conditions and needs of individual birds, but it is still poorly investigated. We focused on a long-distance migrating passerine, the woodchat shrike, in order to investigate for the first time the species' habitat selection at a spring stopover site (island of Antikythira, Greece) after the crossing of the Sahara Desert and Mediterranean Sea. We implemented radio-tracking, color-ringing, and visual behavioral observations to collect data on microhabitat use. Generalized Linear Mixed Models were developed to identify the species' most preferred microhabitat during its stopover on this low human disturbed island. We found that high maquis vegetation surrounded by low vegetation was chosen as perches for hunting. Moreover, high maquis vegetation appeared to facilitate hunting attempts toward the ground, the most frequently observed foraging strategy. Finally, we discuss our findings in the context of conservation practices for the woodchat shrike and their stopover sites on Mediterranean islands. published