Research in the social identity tradition acknowledges the multiplicity of our identities and the implications that identity compatibility has for our health and well-being. However, current measures of multiple group membership have not yet captured the richness and complexity of our social identity networks at the wider sample level, and data regarding the different behaviours typically associated with different group memberships are scarce. Adopting a network approach, we explore the co-occurrence of different group memberships within an individual (identity-by-identity network), the behaviours that are shared among identities (behaviour-by-identity network), and whether identities that are shared also share common behaviours (identity-by-behaviour network). An online survey asked participants (N = 286) to list the groups they are part of, as well as the behaviours viewed to be typical of group members. The networks identified several identities and behaviours to significantly co-occur at a rate both higher and lower than chance. Networks were found to be low in modularity; there was no evidence of clustering within the data. Permutation analyses demonstrated the overall structure of the networks to be significantly different than expected by chance. The co-occurrences identified serve as a meaningful resource for those conducting research into identities, group norms and their associated behaviours.

Endangered Southern Resident killer whales (Orcinus orca) are fish-eaters that preferentially prey on adult Chinook salmon (Oncorhynchus tshawytscha). Despite being salmon specialists, individuals from all three killer whale pods (J, K, L) have been observed harassing and killing porpoises (family Phocoenidae) without consuming them. Retrospectively, we identified and analyzed 78 episodes of Southern Resident killer whales harassing porpoises between 1962 and 2020, of which 28 resulted in the porpoise's death (“phocoenacide”). Fifty-six episodes involved harbor porpoise (Phocoena phocoena), 13 involved Dall's porpoise (Phocoenoides dalli), and the porpoise species was unreported for nine episodes. Southern Resident killer whales often targeted young porpoises that were similar in size to adult Chinook salmon. Both sexes participated in porpoise harassment. Juveniles engaged in the behavior the most; however, their rates of engagement were not found to differ significantly from most other age classes. The behavior was passed through generations and social groupings, as it was first observed in L pod and spread to the other two pods. Killer whales are highly complex animals known to exhibit social learning and cultural transmission of learned behaviors, but the reason(s) for this behavior is unknown. Hypotheses include the social and developmental benefits of play, hunting practice, or displaced epimeletic behavior.

The ultimate payoff of behaviours depends not only on their direct impact on an individual but also on the impact on their relatives. Local relatedness – the average relatedness of an individual to their social environment – therefore has profound impacts on social and life history evolution. Recent work has begun to show that local relatedness has the potential to change systematically over an individual’s lifetime, a process called kinship dynamics. However, it is unclear how general these kinship dynamics are, whether they are predictable in real systems and their impacts on behaviour and life history evolution. In this study, we combine modelling with data from real systems to explore the extent and impact of kinship dynamics. We use data from seven group-living mammals with diverse social and mating systems to demonstrate not only that kinship dynamics occur in animal systems, but also that the direction and magnitude of kinship dynamics can be accurately predicted using a simple model. We use a theoretical model to demonstrate that kinship dynamics can profoundly impact lifetime patterns of behaviour and can drive sex differences in helping and harming behaviour across the lifespan in social species. Taken together this work demonstrates that kinship dynamics are likely to be a fundamental dimension of social evolution, especially when considering age-linked changes and sex differences in behaviour and life history.

Many animals live in societies where individuals frequently interact socially with each other. The social structures of these systems can be studied in depth by means of network analysis. A large number of studies on animal social networks in many species have in recent years been carried out in the biological research field of animal behaviour and have provided new insights into behaviour, ecology and social evolution. This line of research is currently not so well connected to the field of complex systems as could be expected. The purpose of this article is to provide an introduction to animal social networks for complex systems scientists and highlight areas of synergy. We believe that an increased integration of animal social networks with the interdisciplinary field of complex systems, and networks would be beneficial for various reasons. Increased collaboration between researchers in this field and biologists studying animal social systems could be valuable in solving challenges that are of importance to animal social network research. Furthermore, animal social networks provide the opportunity to investigate hypotheses about complex systems across a range of natural real-world social systems. In this article, we describe what animal social networks are and main research themes where they are studied; we give an overview of the methods commonly used to study animal social networks; we highlight challenges in the study of animal social networks where complex systems expertise may be particularly valuable; and we consider aspects of animal social networks that may be of particular interest to complex systems researchers. We hope that this will help to facilitate further interdisciplinary collaborations involving animal social networks and further integration of these networks into the field of complex systems.

Biological systems are typically dependent on transportation networks for the efficient distribution of resources and information. Revealing the decentralized mechanisms underlying the generative process of these networks is key in our global understanding of their functions and is of interest to design, manage and improve human transport systems. Ants are a particularly interesting taxon to address these issues because some species build multi-sink multi-source transport networks analogous to human ones. Here, by combining empirical field data and modelling at several scales of description, we show that pre-existing mechanisms of recruitment with positive feedback involved in foraging can account for the structure of complex ant transport networks. Specifically, we find that emergent group-level properties of these empirical networks, such as robustness, efficiency and cost, can arise from models built on simple individual-level behaviour addressing a quality-distance trade-off by the means of pheromone trails. Our work represents a first step in developing a theory for the generation of effective multi-source multi-sink transport networks based on combining exploration and positive reinforcement of best sources.

. Abstract
. In studies of social behaviour, social bonds are usually inferred from rates of interaction or association. This approach has revealed many important insights into the proximate formation and ultimate function of animal social structures. However, it remains challenging to compare social structure between systems or time-points because extrinsic factors, such as sampling methodology, can also influence the observed rate of association. As a consequence of these methodological challenges, it is difficult to analyse how patterns of social association change with demographic processes, such as the death of key social partners. Here we develop and illustrate the use of binomial mixture models to quantitatively compare patterns of social association between networks. We then use this method to investigate how patterns of social preferences in killer whales respond to demographic change. Resident killer whales are bisexually philopatric, and both sexes stay in close association with their mother in adulthood. We show that mothers and daughters show reduced social association after the birth of the daughter’s first offspring, but not after the birth of an offspring to the mother. We also show that whales whose mother is dead associate more with their opposite sex siblings and with their grandmother than whales whose mother is alive. Our work demonstrates the utility of using mixture models to compare social preferences between networks and between species. We also highlight other potential uses of this method such as to identify strong social bonds in animal populations.
.
. Significance statement
. Comparing patters of social associations between systems, or between the same systems at different times, is challenging due to the confounding effects of sampling and methodological differences. Here we present a method to allow social associations to be robustly classified and then compared between networks using binomial mixture models. We illustrate this method by showing how killer whales change their patterns of social association in response to the birth of calves and the death of their mother. We show that after the birth of her calf, females associate less with their mother. We also show that whales’ whose mother is dead associate more with their opposite sex siblings and grandmothers than whales’ whose mother is alive. This clearly demonstrates how this method can be used to examine fine scale temporal processes in animal social systems.
.

. Many species use social interactions to cope with challenges in their environment and a growing number of studies show that individuals which are well-connected to their group have higher fitness than socially isolated individuals. However, there are many ways to be ‘well-connected’ and it is unclear which aspects of sociality drive fitness benefits. Being well-connected can be conceptualized in four main ways: individuals can be socially integrated by engaging in a high rate of social behaviour or having many partners; they can have strong and stable connections to favoured partners; they can indirectly connect to the broader group structure; or directly engage in a high rate of beneficial behaviours, such as grooming. In this study, we use survival models and long-term data in adult female rhesus macaques (
. Macaca mulatta
. ) to compare the fitness outcomes of multiple measures of social connectedness. Females that maintained strong connections to favoured partners had the highest relative survival probability, as did females well-integrated owing to forming many weak connections. We found no survival benefits to being structurally well-connected or engaging in high rates of grooming. Being well-connected to favoured partners could provide fitness benefits by, for example, increasing the efficacy of coordinated or mutualistic behaviours.
.

Biofumigation is an integrated pest-management method involving the mulching of a glucosinolate-containing cover crop into a field in order to generate toxic isothiocyanates (ITCs), which are effective soil-borne-pest-control compounds. Variation in biofumigation efficacy demonstrates a need to better understand the factors affecting pest-control outcomes and develop best practices for choosing biofumigants, growth conditions, and mulching methods that allow the greatest potential isothiocyanate release. We measured the glucosinolate concentrations of six different commercial varieties of three biofumigant plant species: Brassica juncea (ISCI99, Vitasso, and Scala) Raphanus sativus (Diablo and Bento), and Sinapis alba (Ida Gold). The plants were grown in the range of commercially appropriate seeding rates and sampled at three growth stages (early development, mature, and 50% flowering). Within biofumigant species, the highest ITC-release potentials were achieved with B. juncea cv. ISCI99 and R. sativus cv. Bento. The highest ITC-release potential occurred at the 50% flowering growth stage across the species. The seeding rate had a minor impact on the ITC-release potential of R. sativus but had no significant effects on the ITC-release potentials of the B. juncea or S. alba cultivars.

Resource sharing is an important cooperative behavior in many animals. Sharing resources is particularly important in social insect societies, as division of labor often results in most individuals including, importantly, the reproductives, relying on other members of the colony to provide resources. Sharing resources between individuals is therefore fundamental to the success of social insects. Resource sharing is complicated if a colony inhabits several spatially separated nests, a nesting strategy common in many ant species. Resources must be shared not only between individuals in a single nest but also between nests. We investigated the behaviors facilitating resource redistribution between nests in a dispersed-nesting population of wood ant Formica lugubris. We marked ants, in the field, as they transported resources along the trails between nests of a colony, to investigate how the behavior of individual workers relates to colony-level resource exchange. We found that workers from a particular nest "forage" to other nests in the colony, treating them as food sources. Workers treating other nests as food sources means that simple, pre-existing foraging behaviors are used to move resources through a distributed system. It may be that this simple behavioral mechanism facilitates the evolution of this complex life-history strategy.

A colony of red wood ants can inhabit more than one spatially separated nest, in a strategy called polydomy. Some nests within these polydomous colonies have no foraging trails to aphid colonies in the canopy. In this study we identify and investigate the possible roles of non-foraging nests in polydomous colonies of the wood ant Formica lugubris. To investigate the role of non-foraging nests we: (i) monitored colonies for three years; (ii) observed the resources being transported between non-foraging nests and the rest of the colony; (iii) measured the amount of extra-nest activity around non-foraging and foraging nests. We used these datasets to investigate the extent to which non-foraging nests within polydomous colonies are acting as: part of the colony expansion process; hunting and scavenging specialists; brood-development specialists; seasonal foragers; or a selfish strategy exploiting the foraging effort of the rest of the colony. We found that, rather than having a specialised role, non-foraging nests are part of the process of colony expansion. Polydomous colonies expand by founding new nests in the area surrounding the existing nests. Nests founded near food begin foraging and become part of the colony; other nests are not founded near food sources and do not initially forage. Some of these non-foraging nests eventually begin foraging; others do not and are abandoned. This is a method of colony growth not available to colonies inhabiting a single nest, and may be an important advantage of the polydomous nesting strategy, allowing the colony to expand into profitable areas. Copyright:

Polydomy, a single colony spread between multiple nests, is a widespread life history strategy in ants. The mechanisms by which a polydomous colony functions, and the fitness benefits this nesting strategy provides, are poorly understood. Here we review what is known about polydomy in the well-studied and ecologically important Formica rufa group. We focus particularly on the ecological fitness benefits polydomy may provide to members of the F. rufa group. We discuss the well-documented association in this group between polygyny (multiple queens in a colony) and polydomy, and how this relationship may favour colony reproduction by budding. We argue that although polygyny and reproduction by budding may drive a colony to spread between multiple nests, the maintenance of prolonged communication between these nests needs further explanation in terms of fitness benefits. The potential benefits of polydomy in the F. rufa group are discussed, specifically how polydomy may help a colony: exploit resources, dominate spaces, or lower the cost of stochastic nest destruction. The potential consequences of polydomy for the social organisation of a colony are explored. We also highlight gaps in current knowledge, and suggest future research directions. © 2014 International Union for the Study of Social Insects (IUSSI).

An important problem facing organisms in a heterogeneous environment is how to redistribute resources to where they are required. This is particularly complex in social insect societies as resources have to be moved both from the environment into the nest and between individuals within the nest. Polydomous ant colonies are split between multiple spatially separated, but socially connected, nests. Whether, and how, resources are redistributed between nests in polydomous colonies is unknown. We analyzed the nest networks of the facultatively polydomous wood ant Formica lugubris. Our results indicate that resource redistribution in polydomous F. lugubris colonies is organized at the local level between neighboring nests and not at the colony level. We found that internest trails connecting nests that differed more in their amount of foraging were stronger than trails between nests with more equal foraging activity. This indicates that resources are being exchanged directly from nests with a foraging excess to nests that require resources. In contrast, we found no significant relationships between nest properties, such as size and amount of foraging, and network measures such as centrality and connectedness. This indicates an absence of a colony-level resource exchange. This is a clear example of a complex behavior emerging as a result of local interactions between parts of a system.