The social network structure of a wild meerkat population: 2. Intragroup interactions

Knowledge of the structure of networks of social interactions is important for understanding the evolution of cooperation, transmission of disease, and patterns of social learning, yet little is known of how environmental, ecological, or behavioural factors relate to such structures within groups. We observed grooming, dominance, and foraging competition interactions in eight groups of wild meerkats (Suricata suricatta) and constructed interaction networks for each behaviour. We investigated relationships between networks for different social interactions and explored how group attributes (size and sex ratio), individual attributes (tenure of dominants), and ecological factors (ectoparasite load) are related to variation in network structure. Network structures varied within a group according to interaction type. Further, network structure varied predictably with group attributes, individual attributes, and ecological factors. Networks became less dense as group size increased suggesting that individuals were limited in their number of partners. Groups with more established dominant females were more egalitarian in their grooming and foraging competition interactions, but more despotic in their dominance interactions. The distribution of individuals receiving grooming became more skewed at higher parasite loads, but more equitable at low parasite loads. We conclude that the pattern of interactions between members of meerkat groups is not consistent between groups but instead depends on general attributes of the group, the influence of specific individuals within the group, and ecological factors acting on group members. We suggest that the variation observed in interaction patterns between members of meerkat groups may have fitness consequences both for individual group members and the group itself.     

Conspecific threat,predation avoidance,and resource defense: implications for grouping in langurs

Data on langur (Presbytis entellus) populations were gathered from the literature to test the importance of three selective pressures in determining group size and composition: predation pressure, intergroup resource defense, and conspecific threat. There were no detectable difference in the size of groups in populations facing nearly intact predator communities compared to those populations where predators were severely reduced in number or absent, although there was a trend for the number of adult males per group to increase in areas with nearly intact predator communities. Using population density as an indirect measure of the frequency of intrusions into a group’s home range and thereby as an index of the demographic pressure favoring resource defense, we predicted that higher densities would result in larger defensive coalitions and higher numbers of females per group. This prediction was not upheld. Our third selective pressure, conspecific threat, encompasses those selective forces resulting from physical attack on females, infants, and juveniles. Our index of conspecific threat uses the number of non-group males divided by the number of bisexual groups, because in langurs, the major source of conspecific threat derives from non-group males who, following group take-over, kill infants, wound females, and expel juveniles from groups. This index of conspecific threat was strongly related to the mean number of resident females, was weakly related to the mean group size, but was not related to the number of males in the group. In addition, as predicted, populations with a high index of conspecific threat had higher levels of juvenile expulsion. These analyses were corroborated by a simulation model which used a computer-generated series of null populations to calculate expected slopes of immatures regressed on adult females. These randomly generated populations, matched to means and ranges of real populations, allowed us to determine if deviations of the observed slopes from the expected null slopes could be explained by variation in predation pressure, population density, or conspecific threat. We found no evidence that predation pressure was associated with decreases in immature survival in smaller groups, as would be predicted by the predation-avoidance hypothesis. We found no evidence that immature survival was compromised by small group size in high-density populations, as would be predicted by the resource-defense hypothesis. However, as the index of conspecific threat increased, groups with larger numbers of females were more successful than groups with fewer females in reducing mortality or expulsion of immatures. Overall, conspecific threat received the strongest support as a selective pressure influencing langur group size and composition, suggesting that this selective pressure should be evaluated more widely as a factor influencing composition of animal groups. Received: 23 January 1995/Accepted after revision: 18 February 1996     

Ecology,feeding competition and social structure in baboons

Predictions of the model of van Schaik (1989) of female-bonding in primates are tested by systematically comparing the ecology, level of within-group contest competition for food (WGC), and patterns of social behaviour found in two contrasting baboon populations. Significant differences were found in food distribution (percentage of the diet from clumped sources), feeding supplant rates and grooming patterns. In accord with the model, the tendencies of females to affiliate and form coalitions with one another, and to be philopatric, were strongest where ecological conditions promoted WGC. Group fission in the population with strong WGC was “horizontal” with respect to female dominance rank, and associated with female-female aggression during a period of elevated feeding competition. In contrast, where WGC was low, females’ grooming was focused on adult males rather than other females. Recent evidence suggests that group fission here is initiated by males, tends to result in the formation of one-male groups, and is not related to feeding competition but to male-male competition for mates. An ecological model of baboon social structure is presented which incorporates the effects of female-female competition, male-male competition, and predation pressure. The model potentially accounts for wide variability in group size, group structure and social relationships within the genus Papio. Socio-ecological convergence between common baboons and hamadryas baboons, however, may be limited in some respects by phylogenetic inertia. Received: 22 April 1994/Accepted after revision: 9 December 1995     

Between-group contest competition for food in a highly folivorous population of black and white colobus monkeys (Colobus guereza)

In theory, between-group contest (BGC) competition for food can greatly influence female social relationships and reproductive success in primates, but few studies have investigated whether such effects occur and, if so, under what ecological conditions. There is evidence that adult male black and white colobus monkeys (Colobus guereza, “guerezas”) defend the food their mates need against other groups, suggesting that BGC competition is important in this species. Using data on feeding, ranging, vegetation patterns, and intergroup encounters between six neighboring guereza groups, I provide evidence that the highly folivorous guerezas at Kanyawara, Kibale National Park, Uganda, engaged in BGC competition over unevenly dispersed, relatively high-quality feeding areas or “core areas”. Intergroup aggression was common, and groups’ home ranges overlapped. Groups were more likely to initiate high-level aggression if they encountered another group within or near their core area, and groups that initiated and won encounters often fed in the same areas in which losing groups had fed. Guerezas fed selectively on species with contagious (clumped) distributions and concentrated their feeding efforts in areas of the forest that contained the most food (core areas). Groups could be ranked in a linear dominance hierarchy, and group rank number was inversely related to the quantity and quality of food in groups’ core areas. This study not only provides good evidence that BGC competition occurs in primates but it also reinforces the idea that folivore food resources may be worth defending.     

How do fighting ability and nest value influence usurpation contests in <Emphasis Type="Italic">Polistes</Emphasis> wasps?

Most research on animal contests has focused on the factors that influence the intensity and outcome of aggressive contests within nonsocial species, while relatively little is known about contests in social taxa. Here, we examine contests among queens of the social paper wasp, Polistes dominulus. Queens use multiple reproductive strategies, including nesting alone, usurping established colonies, and cooperatively joining other queens. We stage contests between a nesting queen and a challenger to test how resource value (RV) and resource holding potential (RHP) influence (a) who occupies the nest at the end of the contest and (b) the extent of conflict between the queen and challenger. We found that RHP, as measured by individuals’ facial patterns and body size, influenced the outcome of the contest. Challengers with high RHP were more likely to successfully usurp the nest than challengers with low RHP. Interestingly, queens with relatively high RHP were more likely to form a cooperative association with the challenger than queens with lower RHP, suggesting that queens may evict individuals that are an aggressive threat. RV influenced the intensity of conflict. There was more aggressive conflict over large nests than over small nests. Overall, social taxa have complex contest dynamics with important parallels to contests in nonsocial taxa. Studying contests in social taxa provides an important perspective on the factors that influence individual decisions about conflict versus cooperation.     

Group size but not dominance rank predicts the probability of conception in a frugivorous primate

In social mammals, within-group competition for food can drive variation in female fitness. Frugivores may face particularly strong competition because they use patchily distributed usurpable resources. Dominance rank and group size influence how a female experiences within-group competition. Both are predicted to affect access to food and, thus, reproductive success. We used 15 years of behavioral, demographic, and reproductive data from wild frugivorous blue monkeys to examine effects of rank and group size on the probability that a female conceived. We used generalized linear mixed models, controlling for potentially confounding maternal and environmental factors. Blue monkey females compete aggressively and disproportionately for fruits and exhibit linear dominance hierarchies, but neither rank index we tested significantly predicted the probability of conception. Although earlier studies found that group size effects on activity budgets were minimal, we found that group size had a quadratic relationship with the probability of conception, which peaked at around 31 members. The lack of a rank effect may reflect behavioral strategies (e.g., switching resources, spreading out during feeding, using cheek pouches) that minimize the strength of within-group competition, thus facilitating group-level cooperation in between-group contests. The significant quadratic effect of group size on reproduction may occur if individuals in small groups do not obtain the full benefits of group living (e.g., predator avoidance, increased foraging success, communal care for offspring) and those in large groups experience a lower quality diet or constrained feeding time. Ultimately, measures of reproduction are preferable to behavioral proxies for accurately assessing within-group competition.     

Predictors of food-related aggression in wild Assamese macaques and the role of conflict avoidance

The quality, availability and distribution of food resources and their influence on types and levels of feeding competition play a central role in ecological models of female social structure in mammals. Here, we investigate the impact of social and ecological factors on rates of food-related aggression and the use of potential conflict avoidance mechanisms in wild Assamese macaques (Macaca assamensis) in northeastern Thailand. These questions were addressed by examining feeding competition at the level of individual food patches which provides detailed information on resource characteristics, aggression and feeding party composition. Results suggest that the frequency of aggression in food patches increases with increasing feeding group size and decreasing patch size but is not affected by ecological variables representing resource value (abundance and nutritional value of food items in a patch). Interestingly, females appear to employ several mechanisms to avoid direct conflicts, including the use of alternative feeding sites within food patches, delayed arrival at feeding sites, storing food in cheek pouches and co-feeding with individuals they share strong social bonds with. Conflict avoidance may be partially responsible for the absence of a rank-related skew in female energy intake in this population and may explain other cases where empirical data do not fit the predictions of socio-ecological theory. Our findings also inform the debate about the mechanisms generating fitness benefits from strong social bonds by suggesting that by increasing feeding tolerance, social bonds may enhance resource acquisition, reduce the risk of injuries and lower levels of agonism-related stress.     

The influence of group size on natal dispersal in the communally rearing and semifossorial rodent, Octodon degus

In social or group living species, members of groups are expected to be affected differentially by competition through the effect of group size (i.e., the “social competition hypothesis”). This hypothesis predicts an increase in the probability of dispersal with increasing size of social groups. At a more mechanistic level and based on the known effects of competition on stress hormone levels, a positive relationship between group size and glucocorticoids of juveniles should be observed. We used a demographic approach to test these predictions on a natural population of the communally rearing and semifossorial rodent—Octodon degus. Burrow systems provide degus with places to rear offspring and to evade stressful thermal conditions and predators. Thus, we predicted dispersal to increase with increasing number of degus per main burrow system used, a measure of habitat saturation in degus. The probability of dispersal increased with increasing number of degus per main burrow system used. Mean fecal metabolites of cortisol in offspring increased, yet not statistically significantly, with the number of juveniles in groups. These results were consistent with a scenario in which competition drives natal dispersal in juveniles in social degus. In particular, competition would be the consequence of high degu abundance in relation to the abundance of burrow systems available at the time of offspring emergence.     

Managing conflict between large carnivores and livestock

Large carnivores are persecuted globally because they threaten human industries and livelihoods. How this conflict is managed has consequences for the conservation of large carnivores and biodiversity more broadly. Mitigating human–predator conflict should be evidence‐based and accommodate people's values while protecting carnivores. Despite much research into human and large‐carnivore coexistence strategies, there have been few attempts to document the success of conflict‐mitigation strategies on a global scale. We conducted a meta‐analysis of global research on conflict mitigation related to large carnivores and humans. We focused on conflicts that arise from the threat large carnivores pose to livestock. We first used structured and unstructured searching to identify replicated studies that used before–after or control–impact design to measure change in livestock loss as a result of implementing a management intervention. We then extracted relevant data from these studies to calculate an overall effect size for each intervention type. Research effort and focus varied among continents and aligned with the histories and cultures that shaped livestock production and attitudes toward carnivores. Livestock guardian animals most effectively reduced livestock losses. Lethal control was the second most effective control, although its success varied the most, and guardian animals and lethal control did not differ significantly. Financial incentives have promoted tolerance of large carnivores in some settings and reduced retaliatory killings. We suggest coexistence strategies be location‐specific, incorporate cultural values and environmental conditions, and be designed such that return on financial investment can be evaluated. Improved monitoring of mitigation measures is urgently required to promote effective evidence‐based policy.     

Understanding the Lessons and Limitations of Conservation and Development

Abstract: The lack of concrete instances in which conservation and development have been successfully merged has strengthened arguments for strict exclusionist conservation policies. Research has focused more on social cooperation and conflict of different management regimes and less on how these factors actually affect the natural environments they seek to conserve. Consequently, it is still unknown which strategies yield better conservation outcomes? We conducted a meta‐analysis of 116 published case studies on common resource management regimes from Africa, south and central America, and southern and Southeast Asia. Using ranked sociodemographic, political, and ecological data, we analyzed the effect of land tenure, population size, social heterogeneity, as well as internally devised resource‐management rules and regulations (institutions) on conservation outcome. Although land tenure, population size, and social heterogeneity did not significantly affect conservation outcome, institutions were positively associated with better conservation outcomes. There was also a significant interaction effect between population size and institutions, which implies complex relationships between population size and conservation outcome. Our results suggest that communities managing a common resource can play a significant role in conservation and that institutions lead to management regimes with lower environmental impacts.     

Cost-free vigilance during feeding in folivorous primates? Examining the effect of predation risk,scramble competition,and infanticide threat on vigilance in ursine colobus monkeys (<Emphasis Type="Italic">Colobus vellerosus</Emphasis>)

Vigilance often decreases with increasing group size, due to lower predation risk or greater scramble competition for food. A group size effect on vigilance is seldom seen in primates, perhaps because scanning and feeding often occur simultaneously or because the distinction between routine and induced vigilance has not been investigated. We analyzed feeding and resting observations separately while distinguishing between routine and induced scans in four groups of wild ursine colobus monkeys (Colobus vellerosus) experiencing scramble competition for food and infanticide risk. We used linear mixed-effect models to test the effect of group size, age–sex class, number of neighbors, number of adult male neighbors, and height in the canopy on scanning rates (vigilance) with and without evident conspecific threat. Food type was also examined in the feeding models. Perceived predation risk affected vigilance more than scramble competition for food and infanticide risk. Routine and induced vigilance were greatest at lower canopy heights during feeding and resting and increased when individuals had fewer neighbors while resting. A group size effect was found on induced vigilance while resting, but scanning increased with group size, which probably indicates visual monitoring of conspecifics. Scanning rates decreased while feeding on foods that required extensive manipulation. This supports the idea that vigilance is relatively cost free for upright feeders when eating food that requires little manipulation, a common feature of folivore diets. In the presence of threatening conspecific males, close proximity to resident males decreased individual vigilance, demonstrating the defensive role of these males in the group.     

Within-group spatial position in ring-tailed coatis: balancing predation, feeding competition, and social competition

A variety of factors can influence an individual’s choice of within-group spatial position. For terrestrial social animals, predation, feeding success, and social competition are thought to be three of the most important variables. The relative importance of these three factors was investigated in groups of ring-tailed coatis (Nasua nasua) in Iguazú, Argentina. Different age/sex classes responded differently to these three variables. Coatis were found in close proximity to their own age/sex class more often than random, and three out of four age/sex classes were found to exhibit within-group spatial position preferences which differed from random. Juveniles were located more often at the front edge and were rarely found at the back of the group. Juveniles appeared to choose spatial locations based on feeding success and not predation avoidance. Since juveniles are the most susceptible to predation and presumably have less prior knowledge of food source location, these results have important implications in relation to predator-sensitive foraging and models of democratic group leadership. Subadults were subordinate to adult females, and their relationships were characterized by high levels of aggression. This aggression was especially common during the first half of the coati year (Nov–April), and subadults were more peripheralized during this time period. Subadults likely chose spatial positions to avoid aggression and were actively excluded from the center of the group by adult females. In the Iguazú coati groups, it appeared that food acquisition and social agonism were the major determinants driving spatial choice, while predation played little or no role. This paper demonstrates that within-group spatial structure can be a complex process shaped by differences in body size and nutritional requirements, food patch size and depletion rate, and social dominance status. How and why these factors interact is important to understanding the costs and benefits of sociality and emergent properties of animal group formation.     

Participatory tools for coastal zone management: Use of stakeholder analysis and social mapping in Australia

This paper presents research currently being conducted in Central Queensland, Australia to understand conflicts between coastal zone resource users and the associated sociocultural and political issues surrounding coastal zone management. Conflict occurs between stakeholders in the coastal zone over values, conservation and development trade-offs, access, and resource use rights. Decisions are currently made within a multi-stakeholder framework where there is limited understanding among stakeholders of each groups values and aspirations, and few, mechanisms for negotiation, or to ensure transparency of decisions and feedback on consultation. This paper reports on the contribution of stakeholder analysis and social mapping to conflict management and findings from their application. As it is applied here, stakeholder analysis and social mapping have been successful participatory tools used to document and feed back the values, interests, attitudes and aspirations of stakeholders. Understanding stakeholder conflict is essential in progressing a whole catchment approach to decision-making that secures the cooperation of a diverse range of social groups.     

Scent-marking behavior in wild groups of common marmosets (Callithrix jacchus)

Scent-marking in mammals has been frequently related to within-group social and reproductive dominance and to defense of territory and resources. We studied the scent-marking behavior of five wild groups of common marmosets, Callithrix jacchus, during 5 months of the fruiting season in northeastern Brazil. Circumgenital marking was the most common type of marking. Marks were distributed throughout the home range and were deposited mainly during travel and intergroup encounters. Although marks were commonly deposited at gum trees, there was no evidence that the animals used scent marks to label fruiting trees or sleeping sites. Contrary to expectations, reproductively dominant females did not mark more than reproductively subordinate females. Moreover, during intergroup encounters, reproductively subordinate females displayed higher frequencies of scent-marking than the reproductively dominant females of their group. Our results suggest that scent-marking is not strictly tied to reproductive dominance or territorial (or resource) defense in common marmosets. Because marks provide information about individual identity and reproductive condition, scent marks could serve different functions when used by different individuals. The high frequency of marking by reproductively subordinate females during intergroup encounters suggests that scent-marking might be used to signal to individuals of neighboring groups. Our data highlight the importance of social and ecological variables in scent-marking behavior. Received: 26 October 1998 / Received in revised form: 20 May 1999 / Accepted: 30 May 1999     

Emergence of increased division of labor as a function of group size

Empirical evidence suggests that division of labor in insect societies is positively related to group size both within and across taxa. Response threshold models (RTM) have been commonly used to analyze patterns of division of labor. However, these models have been explored empirically and theoretically for only a limited number of tasks, and few studies have examined predictions of the model as colony size and work availability change. We theoretically examine how group size influences division of labor using a fixed response-threshold model. We simultaneously explore how expected by-products of increased colony size, including demand (total work need relative to total work force available) and task number, affect this relationship. Our results indicate that both low demand and high task number positively influence division of labor. We suggest that these changes parallel what is observed within social groups as their size increases, and that, in part, the commonly observed increased division of labor with increasing group size is emergent.     

Communal nesting is explained by subsequent mating rather than kinship or thermoregulation in the Siberian flying squirrel

Research on group living in animals is concentrated on highly social species, but studying less social species may hint at the factors possibly leading to the evolution of increased sociality. Thermoregulation is often thought to explain communal nesting in solitarily breeding mammals but also other factors may be involved. For example, it is observed that even solitary species may have cryptic kin cooperation. We studied factors affecting communal nesting in the Siberian flying squirrel. Flying squirrels breed solitarily but, similar to most other rodents, adults may sometimes huddle in groups. Communal nesting in flying squirrels was most frequent during winter and autumn, but also occurred during other seasons. This pattern was explained by the breeding season, which took place in the spring–summer, when communal nesting was less common. Neither monthly temperature, after accounting for breeding season, nor daily temperatures in winter explained communal nesting. Group size was small, two to three individuals. In most cases the group was a pair consisting of unrelated male and female, possibly indicating that group formation was related to mating behavior. This study contributes to the understanding of mammalian group formation in two major ways. First, our study contributes to the understanding of the role of relatedness in rodent group formation, demonstrating a case where close relatedness is not related to group formation. Second, our study indicates that in a solitarily breeding, rodent huddling may be more driven by other factors than temperature.     

The evolution of female social relationships in nonhuman primates

Considerable interspecific variation in female social relationships occurs in gregarious primates, particularly with regard to agonism and cooperation between females and to the quality of female relationships with males. This variation exists alongside variation in female philopatry and dispersal. Socioecological theories have tried to explain variation in female-female social relationships from an evolutionary perspective focused on ecological factors, notably predation and food distribution. According to the current “ecological model”, predation risk forces females of most diurnal primate species to live in groups; the strength of the contest component of competition for resources within and between groups then largely determines social relationships between females. Social relationships among gregarious females are here characterized as Dispersal-Egalitarian, Resident-Nepotistic, Resident-Nepotistic-Tolerant, or Resident-Egalitarian. This ecological model has successfully explained differences in the occurrence of formal submission signals, decided dominance relationships, coalitions and female philopatry. Group size and female rank generally affect female reproduction success as the model predicts, and studies of closely related species in different ecological circumstances underscore the importance of the model. Some cases, however, can only be explained when we extend the model to incorporate the effects of infanticide risk and habitat saturation. We review evidence in support of the ecological model and test the power of alternative models that invoke between-group competition, forced female philopatry, demographic female recruitment, male interventions into female aggression, and male harassment. Not one of these models can replace the ecological model, which already encompasses the between-group competition. Currently the best model, which explains several phenomena that the ecological model does not, is a “socioecological model” based on the combined importance of ecological factors, habitat saturation and infanticide avoidance. We note some points of similarity and divergence with other mammalian taxa; these remain to be explored in detail. Received: 30 September 1996 / Accepted after revision: 20 July 1997     

The role of psychology in determining human–predator conflict across southern Kenya

Conflict between people and carnivores can lead to the widespread killing of predators in retaliation for livestock loss and is a major threat to predator populations. In Kenya, a large, rural, pastoralist population comes into regular conflict with predators, which persist across southern Kenya. We explored the social and psychological backdrop to livestock management practices in this area in a process designed to be easy to use and suitable for use across large areas for the study of conflict and transboundary implementation of wildlife conflict reduction measures, focusing on community involvement and needs. We carried out fully structured interviews of livestock managers with a survey tool that examined how social and psychological factors may influence livestock management behavior. We compared survey responses on 3 sites across the study area, resulting in 723 usable responses. Efficacy of individuals’ livestock management varied between and within communities. This variation was partially explained by normative and control beliefs regarding livestock management. Individual livestock managers’ self-reported management issues were often an accurate reflection of their practical management difficulties. Psychological norms, control beliefs, and attitudes differed among sites, and these differences partially explained patterns associated with conflict (i.e., variation in livestock management behavior). Thus, we conclude that a one-size-fits-all approach to improving livestock management and reducing human–predator conflict is not suitable.     

Philopatry, male presence and grooming reciprocation among female primates: a comparative perspective

Competition for food and a safe location in a group are considered to be the main determinants of variation in social relationships among female primates. The effect of the presence of males is usually overlooked, however. Here we put forward two hypotheses connecting the (relative) number of males in a group, a statistic measuring the strength of positive relationships among females (the degree of reciprocity of grooming) and female residence. Under the first hypothesis, we assumed that philopatric females suffer especially from competition for males. Because females of these species are restrained to their native group and thus do not move to groups where better conditions (i.e. more males) prevail, a higher socionomic sex ratio would imply reduced competition and this should be reflected in better relationships among females (i.e. in a higher degree of reciprocation). The second hypothesis is based on the contention of Wrangham (1987) that groups with more males are better able to defend large food sources: in these groups female relationships would suffer less from within-group competition for food. We therefore also expected a positive correlation between the absolute number of males and grooming reciprocation. To test the hypotheses, matrices of grooming interactions were collected by going through the primatological literature. For ten female-resident and four female-transfer primate species, the degree of grooming reciprocation was quantified using a specially adapted matrix statistic. The results favoured the first (competition for males) hypothesis. The degree of grooming reciprocation among females was positively correlated with socionomic sex ratio, but neither with group size nor with the absolute number of males. Correlations between the degree of reciprocity and sex ratio were confirmed at three levels: within the same group at different points in time, between groups of the same species, and between species. In addition, the degree of reciprocation increased with sex ratio more strongly in typical single/variable male than in multi-male species. This we interpreted as a direct consequence of the lower social availability of males for females in multi-male groups than single-male groups. In turn, this effect may be due to males competing for females in multi-male groups. Received: 28 May 1997 / Accepted after revision: 9 November 1997