Group Social Structure Research Articles

Geographic Constraints on Social Network Groups

Social groups are fundamental building blocks of human societies. While our social interactions have always been constrained by geography, it has been impossible, due to practical difficulties, to evaluate the nature of this restriction on social group structure. We construct a social network of individuals whose most frequent geographical locations are also known. We also classify the individuals into groups according to a community detection algorithm. We study the variation of geographical span for social groups of varying sizes, and explore the relationship between topological positions and geographic positions of their members. We find that small social groups are geographically very tight, but become much more clumped when the group size exceeds about 30 members. Also, we find no correlation between the topological positions and geographic positions of individuals within network communities. These results suggest that spreading processes face distinct structural and spatial constraints.

Strength of social tie predicts cooperative investment in a human social network.

Social networks – diagrams which reflect the social structure of animal groups – are increasingly viewed as useful tools in behavioural ecology and evolutionary biology. Network structure may be especially relevant to the study of cooperation, because the action of mechanisms which affect the cost:benefit ratio of cooperating (e.g. reciprocity, punishment, image scoring) is likely to be mediated by the relative position of actor and recipient in the network. Social proximity could thus affect cooperation in a similar manner to biological relatedness. To test this hypothesis, we recruited members of a real-world social group and used a questionnaire to reveal their network. Participants were asked to endure physical discomfort in order to earn money for themselves and other group members, allowing us to explore relationships between willingness to suffer a cost on another's behalf and the relative social position of donor and recipient. Cost endured was positively correlated with the strength of the social tie between donor and recipient. Further, donors suffered greater costs when a relationship was reciprocated. Interestingly, participants regularly suffered greater discomfort for very close peers than for themselves. Our results provide new insight into the effect of social structure on the direct benefits of cooperation.

Characterisation of twenty-one European badger (Meles meles) microsatellite loci facilitates the discrimination of second-order relatives

The European badger (Meles meles) breeds plurally in lowland England and is important economically due to its link with bovine tuberculosis (Mycobacterium bovis) transmission. To understand disease transmission and facilitate effective management, it is vital to elucidate the social structure of badger groups. To improve parentage assignment and the discrimination of relatives, we isolated and characterised 21 polymorphic microsatellite loci in 24 individuals from Wytham Woods, Oxfordshire, UK. These 21 loci increased the discrimination power between full-siblings and half-siblings from 71 to 88%, when added to the existing 31 loci. Similarly, the combined non-exclusion probability increased from 3.0 × 10−8 to 5.8 × 10−13. Newly isolated Mel-592 (FR745854) was X-linked, based on the genotypes of 48 known-sex individuals and will enhance the genetic sex-typing of badgers.

Grooming network cohesion and the role of individuals in a captive chimpanzee group

Social network analysis offers new tools to study the social structure of primate groups. We used social network analysis to investigate the cohesiveness of a grooming network in a captive chimpanzee group (N = 17) and the role that individuals may play in it. Using data from a year-long observation, we constructed an unweighted social network of preferred grooming interactions by retaining only those dyads that groomed above the group mean. This choice of criterion was validated by the finding that the properties of the unweighted network correlated with the properties of a weighted network (i.e. a network representing the frequency of grooming interactions) constructed from the same data. To investigate group cohesion, we tested the resilience of the unweighted grooming network to the removal of central individuals (i.e. individuals with high betweenness centrality). The network fragmented more after the removal of individuals with high betweenness centrality than after the removal of random individuals. Central individuals played a pivotal role in maintaining the network's cohesiveness, and we suggest that this may be a typical property of affiliative networks like grooming networks. We found that the grooming network correlated with kinship and age, and that individuals with higher social status occupied more central positions in the network. Overall, the grooming network showed a heterogeneous structure, yet did not exhibit scale-free properties similar to many other primate networks. We discuss our results in light of recent findings on animal social networks and chimpanzee grooming.

Social Network Analysis of a Criminal Hacker Community

Computer crime hackers have been identified as a primary threat to computer systems, users, and organizations. Much extant research on hackers is conducted from a technical perspective and at an individual level of analysis. This research empirically examines the social organization of a hacker community by analyzing one network called Shadowcrew. The social network structure of this infamous hacker group is established using social networking methods for text mining and network analysis. Analysis of relationships among hackers shows a decentralized network structure. Leaders are identified using four actor centrality measures (degree, betweenness, closeness, and eigenvector) and found to be more involved in thirteen smaller sub-groups. Based on our social network analysis, Shadowcrew exhibits the characteristics of deviant team organization structure.

Effect of social group dynamics on contagion

Despite the many works on contagion phenomena in both well-mixed systems and heterogeneous networks, there is still a lack of understanding of the intermediate regime where social group structures evolve on a similar time scale to individual-level transmission. We address this question by considering the process of transmission through a model population comprising social groups which follow simple dynamical rules for growth and breakup. Despite the simplicity of our model, the profiles produced bear a striking resemblance to a wide variety of real-world examples--in particular, empirical data that we have obtained for social (i.e., YouTube), financial (i.e., currency markets), and biological (i.e., colds in schools) systems. The observation of multiple resurgent peaks and abnormal decay times is qualitatively reproduced within the model simply by varying the time scales for group coalescence and fragmentation. We provide an approximate analytic treatment of the system and highlight a novel transition which arises as a result of the social group dynamics.

Social cohesion in yellow-bellied marmots is established through age and kin structuring

Individual characteristics and choices can influence social structure in animal groups. Social behaviour is likely to change throughout an individual’s life, resulting in different social roles at different ages. Individuals may also choose to interact differently with others based on their age, sex or kinship. We used social network analysis to examine biological correlates of individual social variation in free-living groups of yellow-bellied marmots, Marmota flaviventris. To measure social variation, we chose network measures that reflect an individual’s tendency to initiate or receive both direct and indirect interactions. We asked how age, sex and kinship influenced patterns of affiliative (socially cohesive) and agonistic (socially competitive) interactions. Specifically, we predicted that individuals would vary in their tendency to initiate and receive interactions according to these characteristics, and that they would be more likely to interact affiliatively with more similar individuals and to interact agonistically with more dissimilar individuals. We found that patterns of direct and indirect interactions changed significantly with age, with younger animals being more involved in affiliative interactions and older animals initiating more agonistic ones. Furthermore, affiliative networks tended to be structured by age and kinship. Our results suggest that yearling yellow-bellied marmots are more important for maintaining social cohesion than has previously been recognized, and that marmot colonies are largely organized based on age group and kinship. 2010 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

Genetic Heterogeneity in Wild Isolates of Cellular Slime Mold Social Groups

This study addresses the issues of spatial distribution, dispersal, and genetic heterogeneity in social groups of the cellular slime molds (CSMs). The CSMs are soil amoebae with an unusual life cycle that consists of alternating solitary and social phases. Because the social phase involves division of labor with what appears to be an extreme form of "altruism", the CSMs raise interesting evolutionary questions regarding the origin and maintenance of sociality. Knowledge of the genetic structure of social groups in the wild is necessary for answering these questions. We confirm that CSMs are widespread in undisturbed forest soil from South India. They are dispersed over long distances via the dung of a variety of large mammals. Consistent with this mode of dispersal, most social groups in the two species examined for detailed study, Dictyostelium giganteum and Dictyostelium purpureum, are multi-clonal.

Sex and social networking: the influence of male presence on social structure of female shark groups

Marine predators such as sharks often form single-sex aggregations as part of their diel behavioral cycle. Such aggregations are potentially driven by contrasting reproductive and behavioral strategies between the sexes, leading to distinct sexual segregation. There is, however, no experimental evidence that such predator aggregations are governed by intrinsic social systems, demonstrating long-term temporal stability. Social network structure, temporal stability, and activity profiles were analyzed to examine the impact of introduced males on social structure of 4 captive groups of female catshark (Scyliorhinus canicula). Aside from foraging and habitat selection pressures, we question whether individual female sharks manage additional social demands that potentially influence activity budget and susceptibility to male harassment. Shark groups demonstrated marked differences in their tendency to aggregate in a unisex environment and concomitantly showed significant differences in social response to male presence. Dichotomy in social structure of the 4 groups revealed that well-connected individuals demonstrated greater resilience to male disturbance. Socially isolated females experienced greater levels of partner exchange, reduced temporal stability, and increased activity levels in the presence of males and control females. These results are the first to demonstrate the disruptive influence that male and novel females have on weak female shark social interactions; conversely, aggregations demonstrating relatively strong temporally stable social bonds (at least by some individuals) are particularly resilient to potential male harassment and novel (female) intruders. We highlight that additional ‘social constraints’ may have disparate influence on individuals occupying different structural positions within a network and may thus impact individual fitness unequally. Key words: aggregation, behavior, fish, network analysis, sexual segregation, shark, social structure. [Behav Ecol]

Unavoidable limits on group size in a body size-based linear hierarchy

Competition between individual group members is a key force in shaping social group structure and size. In animal societies, within-group competition may be structured by linear dominance hierarchies, which can be stable if there are minimum differences in competitive ability between adjacently ranked individuals. This requirement constrains maximum group size because only a certain number of clearly differentiated ranks can be fit into the range of competitive abilities between the top and bottom of the hierarchy. We investigated this hypothesis in the body size-based linear dominance hierarchy of the angelfish Centropyge bicolor. Unlike in previous studies, we found that maximum group size in natural C. bicolor groups was not always strictly limited by the range of possible body sizes and the average size difference between adjacent ranks. Oversized groups displayed a compressed body size hierarchy with smaller size differences between adjacent ranks, less effective regulation of subordinate foraging rates to maintain size differences, and greater spatial segregation between adjacently ranked individuals. Our results suggest that when spatial segregation compromises the regulatory mechanisms that maintain clear size hierarchies, groups can become larger than expected by slotting more individuals into a compressed size hierarchy. However, we also found that oversized groups tended to fission into smaller groups, suggesting that they are transient entities and that ultimately the group size limits imposed by the need to maintain a well-defined hierarchy are unavoidable. Key words: Centropyge bicolor, group size, linear dominance hierarchy, maximum group size. [Behav Ecol]

Protection from harvesting restores the natural social structure of eastern wolf packs

Legal and illegal killing of animals near park borders can significantly increase the threat of extirpation for populations living within ecological reserves, especially for wide-ranging large carnivores that regularly travel into unprotected areas. While the consequences of human-caused mortality near protected areas generally focus on numerical responses, little attention has been given to impacts on social dynamics. For wolves, pack structure typically constitutes an unrelated breeding pair, their offspring, and close relatives, but intense harvest may increase adoption of unrelated individuals into packs. Concerns that high human-caused mortality outside Algonquin Park, Canada threatened the persistence of eastern wolves, led to implementation of a harvest ban in surrounding townships. We combined ecological and genetic data to show that reducing anthropogenic causes of mortality can restore the natural social structure of kin-based groups despite the absence of a marked change in density. Since implementation of the harvest ban, human-caused mortality has decreased ( P = 0.000006) but been largely offset by natural mortality, such that wolf density has remained relatively constant at approximately three wolves/100 km 2. However, the number of wolf packs with unrelated adopted animals has decreased from 80% to 6% ( P = 0.00003). Despite the high kinship within packs, incestuous matings were rare. Our results indicate that even in a relatively large protected area, human harvesting outside park boundaries can affect evolutionarily important social patterns within protected areas. This research demonstrates the need for conservation policy to consider effects of harvesting beyond influences on population size.

Theoretical foundations for enhancing social connectedness in online learning environments

Group social structure provides a comfortable and predictable context for interaction in learning environments. Students in face‐to‐face learning environments process social information about others in order to assess traits, predict behaviors, and determine qualifications for assuming particular responsibilities within a group. In online learning environments, however, negotiating social information and maintaining social connectedness can pose challenges for participants. Nonverbal strategies one typically uses for enhancing communication and overcoming ambiguity – such as an approving smile or a questioning brow – must be approached differently while learning online where fewer sensory communication channels are typically available. We present the theoretical foundation for how social information processing and group structure theories may be combined to assist instructional designers in further examining the social system perceived by the online learner. We propose a framework for thinking more systematically about the development of group social structure in online learning environments.

Dynamics of social roles in a knowledge management community

With the emergence of community-oriented Information and Communication Technology (ICT) applications, e.g., Wikipedia, the popularity of socio-technical phenomena in society has increased. This development emphasises the need to further our understanding of how computer-supported social group structures change over time and what forms emerge. This contribution presents the results of a qualitative field study of a Socio-Technical Community (STC). The STC is described from its founding (in 2001) to its sustainable development (in 2006) as well as its transformation phase (2007–2008). The design-based research approach revealed changes of social structures by social roles within the STC over time. The central conclusion is that such STC’s – networks of computer-mediated communication and human interaction – evolve a specific kind of social structure, which is formal rather than informal. The results indicate that a group evolves from an informal trust-based community with few formal roles to a STC where the social mechanisms, and not the software architecture, supports knowledge management processes.

Characteristics of a group of Hubei Golden Snub‐nosed Monkeys (Rhinopithecus roxellana hubeiensis) before and after major snow storms

Natural disasters can negatively affect primate population demography and social group structure. A clear understanding of these effects has important implications for wildlife conservation. The worst snow storms in nearly five decades hit portions of southern and central China between January 10 and February 6, 2008, presenting a unique opportunity to observe their immediate effects on a previously studied group of Hubei Golden Snub-nosed Monkeys (Rhinopithecus roxellana hubeiensis) in temperate forests in Shennongjia Nature Reserve, Hubei Province, China. We recorded social and demographic characteristics of the group before and after the snow storms. The average group size decreased from 270 individuals before the storms to 197 individuals after the storms, a reduction of 27.2%. Adult females (30.1%), juveniles (38.1%) and infants (55.4%) suffered higher mortality than did adult males (15.7%). Despite age and sex-based differences in mortality, the ratios of adult males to adult females, adults to immatures and adult females to immatures remained similar before and after the storms. However, higher mortality among females, juveniles and infants may reduce the group's long-term potential for growth.

Model for Revelation of Unfriendly Information Impacts in Mass-Media Which are Directed on Change of Public Opinion

In this article we proposes the mathematical model for revelation of deliberate unfriendly information impacts which are fulfilled by means of specially prepared information messages (news, reviews and others) in mass-media. The model calculates the quantitative measure for fact determination of purposeful information impact and evaluation of potential damage to interests of state (party, corporation) from impact fulfilment. The model use the following data: intensity and direction of information streams (publication frequency and themes of news), structure of important state and public problems, structure of social groups of a society, priorities of these social groups, mass-media popularity in social groups, priorities of a state policy. The model is the semantic network in which the relations between concepts we formalize by use of fuzzy measures by Sugeno. We have used this model for revelation of information impacts on public opinion of Russian-speaking national minority of Crimea (Ukraine) during 01.2002 - 02.2005 (final stage of presidential elections). The model also can has important implications for evaluation of election cleanness, for neutralization of dirty voting technologies, for facts determination of unfair competition, when corporations involve a public opinion into own competitive activity.

Reproductive conflict delays the recovery of an endangered social species

1. Evolutionary theory predicts that individuals, in order to increase their relative fitness, can evolve behaviours that are detrimental for the group or population. This mismatch is particularly visible in social organisms. Despite its potential to affect the population dynamics of social animals, this principle has not yet been applied to real-life conservation. 2. Social group structure has been argued to stabilize population dynamics due to the buffering effects of nonreproducing subordinates. However, competition for breeding positions in such species can also interfere with the reproduction of breeding pairs. 3. Seychelles magpie robins, Copsychus sechellarum, live in social groups where subordinate individuals do not breed. Analysis of long-term individual-based data and short-term behavioural observations show that subordinates increase the territorial takeover frequency of established breeders. Such takeovers delay offspring production and decrease territory productivity. 4. Individual-based simulations of the Seychelles magpie robin population parameterized with the long-term data show that this process has significantly postponed the recovery of the species from the Critically Endangered status. 5. Social conflict thus can extend the period of high extinction risk, which we show to have population consequences that should be taken into account in management programmes. This is the first quantitative assessment of the effects of social conflict on conservation.

162 REPRODUCTIVE CYCLES, PREGNANCY AND REVERSAL OF LONG TERM ACYCLICITY IN CAPTIVE SOUTHERN WHITE RHINOCEROS AT HAMILTON ZOO

In 1999, the New Zealand captive population of Southern white rhinoceros (Ceratotherium simum simum) was increased with the addition of six wild-caught founders. We report on the breeding success of two females (est. 5 to 6 years at import) and a female born in 2000 (conceived in the wild). Fecal samples were collected 1 to 3 times per week from females (n = 3) for several periods (5 to 24 months) between 2000 and 2008. Reproductive cycles and pregnancy were characterized using fecal progestogen concentrations, observations of courtship behaviour and parturition dates. The average length of the reproductive cycle was 31.6 ± 0.6 days (range 26–38 days, n = 34 cycles). Four pregnancies were confirmed in one female with a sex ratio of 1 female to 3 males (including 1 male loss at an estimated 5 months of gestation), known gestation lengths were 514 and 507 days. In the non-reproducing adult female, long cycles (67.2 ± 1.3 days, n = 5) were detected in addition to regular cycles (31.9 ± 0.9 days, n = 13) during the first 3 years in captivity, consistent with previous reports (Schwarzenberger F et al. 1998 An. Repro. Sci. 53, 173–190; Brown JL et al. 2001 Zoo Biol. 20, 463–486). The absence of breeding behavior and low progestogen concentrations for an extended 4-year period was cause for concern for the Australasian Species Management Programme managers (Hermes R et al. 2004 An. Repro. Sci. 82–83, 49–60; Hermes R et al. 2006 Theriogenology 65, 1492–1515). In 2007, the social structure of the Hamilton Zoo rhinoceros group was altered by exchanging the breeding male and two male offspring for a wild-caught male from Auckland Zoo. Within two months of arrival the long-term acyclic female had resumed cycling and had conceived six months after introduction of the new male. The young captive-born female continued to have regular length cycles and mating was observed with the new male. Recently, early embryonic loss was determined by ultrasound in the young female having a long 70 day cycle determined by fecal analysis. Fecal progestogen concentrations were useful for diagnosing pregnancy after 3 months gestation with concentrations four times higher than luteal phase concentrations by 9 to 12 weeks after mating (n = 3). Two females exhibited seasonal acyclic periods characterized by low progestogen concentrations corresponding to decreasing daylength (autumn and winter months). Fecal progestogen monitoring of reproductive status and pregnancy combined with behaviour observations has provided valuable information for breeding management decisions and planning for parturition in this population. The reversal of long-term acyclicity and a resulting pregnancy that represents two original founders is particularly significant for the genetic diversity of the Australasian population of white rhinoceros.

Sociality of the dispersing sex: the nature of social bonds in West African female chimpanzees, Pan troglodytes

Patterns of group social structure are often linked to the competitive regime within a social unit and to the availability of kin. In line with this, many studies have shown that the dispersing sex, which is considered to have fewer kin around, is less social, while the philopatric sex has strong social bonds. Chimpanzees were considered to fit well into this scheme with highly social and competing philopatric males and generally asocial and solitary dispersing females. However, recent data suggest that chimpanzee females can indeed be highly social, even though they are unlikely to be related to each other. We

Effects of a running wheel-igloo enrichment on aggression, hierarchy linearity, and stereotypy in group-housed male CD-1 (ICR) mice

Environmental enrichment is an important strategy to improve the welfare of laboratory animals. Running wheels might serve as enrichment devices for laboratory mice, since mice use them extensively when they are provided. However, competition among group-housed mice for such highly preferred enrichment devices could also lead to injurious aggression. We therefore assessed the effects of providing a running wheel-igloo enrichment on the social behaviour of group-housed male mice. CD-1 (ICR) mice ( n = 60, 20 per treatment) were housed in standard polycarbonate cages (five mice per cage) for 2 weeks (BASE), and then placed in either: (1) a standard cage with bedding (CONTROL), or (2) same as CONTROL, but with the addition of a Bio-Serv ® mouse running wheel-igloo (WHEEL) or (3) same as WHEEL, but with the running wheel glued in place so that it could not rotate (FIXED). Social behaviour and dominance ranks were assessed at the end of BASE and 2 weeks after imposition of treatments. There was increased escalated aggression in both enriched cages (FIXED, Tukey: T 8 = −8.31; P = 0.0003; WHEEL, Tukey: T 8 = −4.577; P = 0.0153), and decreased stereotypy in WHEEL (Tukey: T 8 = 4.226; P = 0.0237). There was also a decrease in dominance hierarchy linearity in enriched treatments (FIXED, Tukey: T 9 = 3.653; P = 0.0433; WHEEL, Tukey: T 9 = 6.273; P = 0.0014) and a negative correlation between hierarchy linearity and escalated aggression overall (GLM: F 1,7 = 61.41; P < 0.001; partial r = 0.90). Thus, providing the running wheel-igloo enrichment had a negative effect in that it increased potentially injurious aggression. Additionally, the decrease in hierarchy linearity suggests that the social structure in enriched groups was disrupted. The cause of the decrease in cage stereotypies in WHEEL is unknown, but could be because these stereotypies were re-directed towards stereotypic wheel-running, or because wheel-running reduced frustration due to limited opportunities for exploratory locomotion or caused a shift in the behavioural time budget. Despite this decrease in stereotypy, this form of enrichment is not beneficial for group-housed male CD-1 mice due to the associated increased aggression. However, female mice or males of less aggressive mouse strains might respond differently, and singly housed mice should generally benefit from such enrichment.

The influence of social structure on the propagation of social information in artificial primate groups: A graph-based simulation approach

Observations of primate groups have shown that social learning can lead to the development of temporal stable traditions or even proto-culture. The social structure of primate groups is highly diverse and it has been proposed that differences in the group structure shall influence the patterns of social information transmission. While empirical studies have mainly focused on the psychological mechanisms of social learning in individuals, the phenomenon of information propagation within the group has received relatively little attention. This might be due to the fact that formal theories that allow actual testing have not been formulated, or were kept too simple, ignoring the social dynamics of multi-agent societies. We want to propose a network approach to social information transmission that (1) preserves the complexity of the social structure of primate groups and (2) allows direct application to empirical data. Results from simulation experiments with artificial group structures confirm that association patterns of group-members influence the expected speed of information transmission during the propagation process. Introducing a forgetting rate shows that under certain conditions the proportion of informed individuals will reach a stable rate in some systems while it will drop to zero in others. This suggests that the likelihood to observe temporal stable traditions shall differ between social systems with different structure.