Group Social Structure Research Articles

Safe selfish sentinels in a cooperative bird

SummarySentinel behaviour involves a unique cooperative system of dedicated look‐outs which protect members of their social group from attack by predators. Using detailed observations from groups of Arabian babblers,Turdoides squamiceps,we tested the original theoretical suggestion that cooperative sentinel systems are simply the result of individually selfish state‐dependent patterns of behaviour.Sentinel effort and the number of sentinel bouts per individual per hour were greater for males than females, and both increased with individual dominance status within the group.Sentinel behaviour was unaffected by group social structure, in terms of patterns of relatedness and the number of potential breeders.Total group sentinel effort increased with group size, while the effort per individual decreased irrespective of sex and dominance rank. Simultaneous sentinel behaviour by two or more birds was very rare, but increased with group size.Sentinel effort followed seasonal fluctuations in food availability, but not peaks of raptor migration through the study site.Body mass was greater for males than females and was positively related to dominance rank. Overall, body mass explained much of the variation in individual sentinel effort both within and between birds. However, data on individual foraging performance could not be related to changes in body mass and thus to differences in sentinel effort.Sentinel behaviour in groups of Arabian babblers therefore confirms many of the predictions arising from state‐dependent models of cooperative, yet individually selfish, sentinel behaviour.

The Many Faces of SocialIdentity: Implications for Political Psychology

Social identity is a concept that has been invented and reinvented across the social and behavioral science disciplines to provide a critical link between the psychology of the individual and the structure and function of social groups. This paper reviews the various definitions of social identity as it is used in different theoretical frameworks, drawing distinctions among person‐based identities, relational (role‐based) identities, group‐based identities, and collective identities. The implications of these different conceptualizations of social identity for political psychology are discussed, with a call for integrative theory that draws on all four definitions interactively.

Microsatellite analysis of genetic variation among and within Alpine marmot populations in the French Alps.

The genetic structure of the Alpine marmot, Marmota marmota, was studied by an analysis of five polymorphic microsatellite loci. Eight locations were sampled in the French Alps, one from Les Ecrins valley (n = 160), another from La Sassière valley (n = 289) and the six others from the Maurienne valley (n = 139). Information on social group structure was available for both Les Ecrins and La Sassière but not for the other samples. The high levels of genetic diversity observed are at odds with the results obtained using microsatellites, minisatellites and allozymes on Alpine marmots from Germany, Austria and Switzerland. Strong deficits in heterozygotes were found in Les Ecrins and La Sassière. They are caused by a Wahlund effect due to the family structure (i.e. differentiation between the family groups). The family groups exhibit excess of heterozygotes rather than deficits. This may be caused by outbreeding and this is compatible with recent results from the genetics of related social species when information on the social structure is taken into account. The observed outbreeding could be the result of females mating with transient males or males coming from neighbouring colonies. Both indicate that the species may not be as monogamous as is usually believed. The results are also compatible with a male-biased dispersal but do not allow us to exclude some female migration. We also found a significant correlation between geographical and genetic distance indicating that isolation by distance could be an issue in marmots. This study is the first that analysed populations of marmots taking into account the social structure within populations and assessing inbreeding at different levels (region, valley, population, and family groups). Our study clearly demonstrated that the sampling strategy and behavioural information can have dramatic effects on both the results and interpretation of the genetic data.

Multidimensional scaling analyses of the perceived social structure of informal groups.

Multidimensional scaling analyses of the perceived social structure of informal groups.

Reproducing Social Structure in Task Groups: The Role of Structural Ritualization

Reproducing Social Structure in Task Groups: The Role of Structural Ritualization

Determining groups from the clique structure in large social networks

Abstract Ethnographers have traditionally defined human groups as disjoint collections of individuals who are linked to each other by regular interaction, shared perceptions and affective ties. They are internally differentiated: some members occupy a central position in the group, others are on the periphery or somewhere in between. This way of characterising a group is intuitive to seasoned observers but social network analysts seek a more systematic method for determining groups. Freeman [Freeman, L.C., 1996. Cliques, Galois lattices, and the structure of human social groups, Social Networks 18, 173–187.] describes a formal model based on the concept of overlapping social network cliques. Freeman's analysis produces results that are consistent with ethnographic results but his technique is not easily implemented for very large data sets. This paper describes two algorithms based on Freeman's clique–lattice analysis. The first implements his technique exactly; the second is a modification that exploits the clique structure, thereby enabling the analysis of large complex networks. We apply both algorithms to a real data set and compare the results.

The evolution of infanticide: genetic benefits of extreme nepotism and spite

Among patterns of naturally occurring infanticide, one of the most interesting is the killing of young by lactating adult females in several mammalian species. In different species, the litters of either distantly related mothers or of close relatives have been documented as victims. We examined possible genetic benefits of infanticide by adult females using models of inclusive fitness and coancestry. Infanticide is viewed as a form of nepotism, in which offspring that are closer relatives of the infanticidal marauder have a greater chance of recruiting into a breeding group following infanticide. In this context, the genetic relationship of marauders and the young they kill is based upon the competitive social environment within breeding groups of adults. Two models were developed, based on linear and curvilinear changes in the fitness of mothers that either protect their litters or leave their litters unprotected while they maraud the litters of other adult females. Forms of these models that describe genetic polymorphisms of infanticide and ESS (evolutionary stable strategy) frequencies of infanticide yield quantitatively similar results. The models suggest that a balance should occur within populations between marauding and protection of young. At equilibrium, infanticide appears to be a spiteful behavior because it lowers the reproductive success of both the marauder (due to leaving their litters unattended and thus subject to other marauders) and mothers that try to protect their litters (because at least some maraudings are successful). Further, high levels of coancestry among females in a social breeding group should not change the frequency of infanticide when the population is at the equilibrium frequencies of marauding and protecting. Thus, in breeding groups made up of matrilines of highly philopatric females, infanticide of young genetically related to the marauder might be expected. Conclusions drawn from the models are supported by patterns of infanticide in ground-dwelling squirrels, where extensive information on infanticide exists and the social structure of breeding groups varies among species.

Modeling the influence of settlement structure on the spread of influenza among communities.

Several factors play critical roles in the geographic spread of infectious diseases, including the movement of people between communities and the social and economic structure of groups of communities. A mathematical model has been developed to examine the individual and shared impact of these factors. This model was applied to the spread of the 1918-1919 influenza epidemic in three Aboriginal communities in central Canada. Previously published results from simulations of the model used parameter estimates for mobility patterns that were derived from historical documents from the study communities, especially Hudson's Bay Company post journals. We have termed this model the Frontier pattern. In this paper we extend that work to consider the consequences of three additional travel scenarios, which represent idealized trade and travel relationships between different communities. The three patterns include (a) the Central Marketplace scenario, an idealization of relations between a central community and its satellites in which a single central community satisfies all needs of the satellite communities; (b) the Sister Towns scenario, which allows travel among all communities and overemphasizes communication between satellites so that the ramifications of small town interactions are easier to observe; and (c) the Circuit scenario, which represents a hypothetical trade network that is a series of unidirectional dyad relationships linking all communities within a region. Results from simulations of the four mobility patterns are compared to assess the potential impact different social and economic relationships among communities may have had on the geographic spread of the 1918 influenza epidemic in central Canada and in other regions. These results reinforce conclusions that show that variation in patterns of mobility significantly influences the timing of epidemic peaks but only minimally alters the number of cases within a community. In addition, comparisons of the different models indicate that a central location in the social and political hierarchy of a region may be more important in influencing patterns of epidemic spread than just a central location with regard to travel patterns. Furthermore, who was actually travelling and where they were travelling had important consequences for epidemic spread. Am. J. Hum. Biol. 12:736-748, 2000. Copyright 2000 Wiley-Liss, Inc.

Cooperative Breeding in Marmots

Whenever individuals live in stable social groups and not all individuals breed, group members may breed cooperatively. While well-documented in a variety of birds and mammals, there is some controversy over whether, and to what degree, sciurid rodents breed cooperatively. We identify cooperative breeding when: individuals delay dispersal beyond reproductive maturity, reproduction in mature individuals is suppressed, and when non-breeders provide alloparental care. In this paper we note that the 14 species of marmots (Marmota spp.), large ground-dwelling sciurid rodents found throughout the Northern Hemisphere, provide an excellent taxon in which to study the evolution of cooperative breeding. Marmot species fit none, some, or all of the attributes of cooperative breeding. Most interestingly, delayed dispersal and alloparental care may be de-coupled interspecifically, and possibly intraspecifically, making marmots an excellent taxon for additional study. Environmental harshness increases maturation time and is associated with dispersal delayed beyond reproductive maturity. The opportunity to gain direct fitness may be associated with gaining indirect fitness by alloparental behavior. In addition to its theoretical attraction, cooperative breeding has profound implications for conservation and management of species that breed cooperatively. To maximize marmot production, managers and breeders need to pay particular attention to social group structure to prevent the expression of reproductive suppression. If cooperative breeding results from an environmental constraint, habitat modifications may increase the percent of females that breed.

Changes in behavior in free-ranging Lemur catta following release in a natural habitat.

The adjustment of captive-reared and developmentally deprived ringtailed lemurs (Lemur catta) to supported release on St. Catherine's Island, Georgia, was studied over 7 years to examine if these animals developed behavior comparable to wild populations. Initial changes after release included decreased obesity and increased agility as well as foraging for appropriate novel plants. Ranging, daily behavior cycles, and vocalizations developed more slowly over 1-3 years, but eventually the behavior resembled that of wild groups. Group composition and social structure changed through conflict to resemble wild and captive troops in social organization, including the emergence of matrilineal dominance and male emigration. Since behavior eventually resembled that seen in the wild, some resilience of species-typical wild behavior in captivity is supported.

Explaining culture: A naturalistic approach By Dan Sperber (review)

460 LANGUAGE, VOLUME 74, NUMBER 2 (1998) grammatical functions. Clearly, in such cases the reflexive clitic does not function as an a-structure binder as described above. A therefore ascribes a second function to the reflexive clitic in Catalan: It may also optionally identify the 'referential indices' oftwo arguments in a-structure. However, both functions ultimately lead to the same effect, namely the colinking of different arguments to the same semantic participant. Thus one might wonder whether a more uniformanalysis couldbeprovidedtreatingthis kind of colinking as the basic function of the reflexive clitic and trying to derive other effects such as a-structure binding from independent (mapping) principles. A's book is highly recommended to linguists interested in syntactic theory as it covers central syntactic topics such as reflexive clitics and causative constructions . It offers new perspectives on the formal architecture of LFG but will also be of interest to linguists from different theoretical backgrounds. Scholars working on Catalan or on Romance in general will be provided with interesting analyses and new insights into the structure of these languages. [Lutz Gunkel, Freie Universität Berlin.] Explaining culture: A naturalistic approach . By Dan Sperber. Oxford: Blackwell, 1996. Pp. 175. Paper $18.95. The way one tries to explain a cultural fact follows from what one takes the nature of cultural facts to be. The same is true of linguistic facts; for Saussure, for example, linguistic facts were entities in a realm of their own, connected but not reducible to individual psychological facts. The cognitive revolution has given us a naturalistic reduction of linguistic facts. These are now taken to be configurations in the mind/brain ofan individual speaker, and so theirevolution is best explained as the interaction of that speaker's inherent cognitive mechanisms and the data to which he is exposed. In a large body of work over the last fifteen years, Sperberhas been attempting a naturalistic interpretation for the facts of culture. The six essays brought together in Explaining culture represent an overview of this work. Cultural facts, for S, are not Platonic entities but representations in the mind/brain of human individuals. This definition raises a problem which Noam Chomsky's parallel conception of Ilanguage does not face. That is, whereas linguistic representations remain linguistic even if found in only one speaker, cultural representations are only cultural by virtue of being shared by a community. S must therefore expand his definition to state that cultural representations are that subset of all mental representations which come to be widely shared in a particular community. On this definition, there is no discontinuity, oreven clear dividing line, between cultural representations and individual ones. S's approach to cultural facts is epidemiological. To give an epidemiological explanation is to show how and why a particular representation came to be distributed as it did across the minds of a human group. The factors involved will be ecological —some aspect of the group's lifestyle or social structure helped spread the representation in question —and also psychological. As S argues, human cognition systematically transforms representations by processing them. An example here is that of an oral folk tale which, to persist culturaUy, has to be remembered between tellings and also to remain attractive to audiences. These factors wiU cause it to evolve towards a form which is most memorable and relevant to the human mind. Note that this evolution is not a process of random mutation and selection. Rather, cognition exerts definite directional transformations on the representations it deals with. There are obvious parallels here with functionalist work in hnguistics, and, overall, there are plenty of ideas to interest the linguist in this volume. The essays are, however, speculative and poorly backed up with examples. Despite some brave rhetoric about the possibility of a science of culture, the approach is totally programmatic. I have not seen a single weUworked empirical explanation using the epidemiological approach. Nor is it clear how this would be done; we might explain the persistence ofa religious belief by asserting that it was specially relevant to some group of people, but how would we know that this was so? Presumably by observing how persistent it was. Until this circle is broken...

Urban Decline and the New Social and Ethnic Divisions in the Core Cities of the Italian Industrial Triangle

This paper examines the new social division of the city cores in the metropolitan areas of Milan, Turin and Genoa. The changing structure and location of social and ethnic groups are analysed using census data from 1981 and 1991. Special emphasis is given to the relationships between de-urbanisation and social polarisation; and between urban economic restructuring and new forms of distribution or social groups. Contrary to theories of population de-urbanisation which suggest an associated decrease in social polarisation, the analysis presented in this paper demonstrates increasing levels of social division of space.

Preferences for Nest Boxes as Environmental Enrichment for Laboratory Mice

AbstractIn nature, mice live in burrows with nest chambers where they breed and may hide from predators. In the laboratory, a shelter or refuge is an easily applicable form of enrichment which may enhance the welfare of laboratory mice by giving them more control over their environment. Six nest boxes made of different materials were evaluated in a preference test with male and female mice of two strains (C57BL/6J and BALB/c). In general, mice showed a preference for cages with a nest box made of grid metal as compared to clear or white perspex nest boxes, or no nest box. They also showed a preference for a cage with a nest box of perforated metal as compared to nest boxes made of grey PVC or sheet metal, or no nest box. When offered a nest box with one open side or a nest box with two open sides, most mice preferred the nest box with one open side and were observed to lie in it with their heads directed towards the opening.The results of this study show that nest boxes may be used for enrichment purposes in caged mice, although it is not yet entirely clear what are the main features influencing the animals’ preferences. When providing nest boxes as shelters, the structure and design of this type of enrichment should be taken into account, because these may have an effect on the social structure of groups of mice.

Consistency of measurement of social status in sows housed in two group dry-sow systems

A wide range of measures have been employed in an attempt to determine social structure in groups of animals and different analyses of social behaviour may result in the construction of different hierarchies (Tomback et al. 1989). In order to investigate social aspects of welfare in group-housed sows it is important to establish a meaningful measure of group dynamics. We therefore wished to establish whether different measures of social status resulted in the construction of similar hierarchies in dry-sows housed in indoor or outdoor group-housing systems.

Consistency of measurement of social status in sows housed in two group dry-sow systems

A wide range of measures have been employed in an attempt to determine social structure in groups of animals and different analyses of social behaviour may result in the construction of different hierarchies (Tomback et al. 1989). In order to investigate social aspects of welfare in group-housed sows it is important to establish a meaningful measure of group dynamics. We therefore wished to establish whether different measures of social status resulted in the construction of similar hierarchies in dry-sows housed in indoor or outdoor group-housing systems.

Behavioural response of a Western lowland gorilla Gorilla gorilla gorilla group to the loss of the silverback male at Zoo Atlanta

At Zoo Atlanta in December 1994 a silverback ♂ Western lowland gorilla Gorilla gorilla gorilla group leader died of cardiovascular disease. The behavioural responses of the remaining members of the group were studied and a variety of individual and social behaviours was recorded. For 3 months following the death of the ♂ there was a significant increase in aggressive display behaviours, such as lunge, quadrupedal stiff stance, displace and head divert, and the mother‐offspring relationship intensified. An understanding of the ‘control role’ of the silverback ♂ and the behaviour of group members following changes in social group structure can help zoo managers plan their management strategy when periods of social change are unavoidable.

Relation of Intergroup Variation in Allogrooming to Group Social Structure and Ectoparasite Loads in Red Howlers (Alouatta seniculus)

We compare the allogrooming behavior of 5 troops (average size = 8.2) of red howlers (Alouatta seniculus) from the Venezuelan Llanos with that of other A. seniculus and Alouatta spp. of the genus. In 126.9 observation hr, we recorded 118 allogrooming events, with an average bout length of 109 sec. Females groomed more frequently than males did, but as groomees there is no significant differences between sexes. Adult males groomed adult females mostly in a sexual context (before copulation). Allogrooming rates differ significantly among groups. There are also significant differences among members of the same troop both as groomers and groomees, which we explain in the context of the social behavior and history of each troop. There is no significant correlation between weight of the groomee and duration of the grooming bout. However, the examination of grooming rates and ectoparasite load suggests that allogrooming may have hygienic consequences. Differences in allogrooming rates among species of Alouatta are related to differences in group kin structure and patterns of female competition, in particular, coalition formation. We conclude that the social structure and the degree of relatedness among individuals within a group (or among individuals in a population in interpopulation comparisons) is a more important determinant of allogrooming rate than body size or group size. Our results emphasize the importance of considering intergroup and interpopulational variation in behavior.

Recent Advances in the Study of Bats

This broadly based volume brings together the twenty-one papers presented at the Seventh International Bat Research Conference in Aberdeen in August 1985 on Flight, Echolocation and Social and Reproductive Biology. These areas of research have seen the most significant advances in recent years and new results are presented and analysed by leading international authorities. The volume includes piipets on the origin, aerodynamics and physiology of flight, on behavioural studies of echolocation including interactions between bats and insects, on narrow band frequency analysis by echolocating bats, on the genetic structure of social groups, alxruism and cooperation, on the energetics of reproduction, and on the activity of the hypothalamo-hypopbyseal-gonad axis in seasonally breeding bats. This volume will be of interest to all who are interested in bats as supreme examples of evolutionary adaptation.

Genetic Diversity in Hominoid Primates

Humans are only one of the species produced by the hominoid evolutionary radiation. Common and pygmy chimpanzees (our closest relatives), gorillas, orangutans, and the lesser apes also belong to this group. In humans, patterns of genetic variation are becoming increasingly better characterized by modern molecular methods. Understanding human variation in an evolutionary context, however, requires comparison of human patterns with those of other hominoids, to reveal features shared among hominoids and those unique to humans. Genetic variation among chimpanzees, gorillas, and orangutans is beginning to be characterized, so that comparisons are now possible. From genetic data, several different kinds of information can be reconstructed, including the evolutionary relatedness of subspecies and populations, time estimates for evolutionary divergences, past population dynamics, extent of gene flow over geographical landscapes, and group social structure. Knowledge of hominoid genetic variation is also relevant to applied fields such as primate conservation and medicine.

The Development of Social Networks in Preschool Children

Behavioral observations and sociometric ratings were assessed in separate 3- and 4-year-old child care classes across a two year period. A cross sequential design included three cohorts. Cohort A was observed at age 4, Cohort B at ages 3 and 4 and Cohort C was observed at age 3 yielding two separate cross sectional comparisons and a longitudinal comparison across ages 3 and 4. Social network analyses were used to determine the relation between behavioral measures of social interactions and sociometric ratings, developmental changes in the degree of organization of the social networks in each class, and the degree to which gender was an organizing principle in the social structure of both age groups. In general, correspondence between the behavioral observations and sociometric ratings increased with age and the social structure showed greater cohesion in the 4-year-old class. Gender was an organizing principle in the social structure of the 4-year-old class and became more apparent across time in the 3-year-old class. Implications of the findings for the assessment of sociometric status and for intervention are discussed.