A new interpretation of the social organization and mating system of the Callitrichidae

Tamarins and marmosets are usually described as monogamous, or as living in extended family groups. Field research on a variety of callitrichid species shows, however, that immigration and emigration by adults are common and that groups are likely to be composed largely of unrelated adults of both sexes. Despite the number of adult females present in a group, only a single female is usually reproductively active. This female may mate with more than one male. Care for the young is provided by all group members but principally by adult males. This generally is referred to as a “communal breeding system. ” However, a vertebrate social system in which more than two reproductively active adults participate in infant care is rare and has otherwise been reported only in a small number of avian and canid species. Wild callitrichid groups virtually always include helpers, but the number of adults of each sex is highly variable. We propose that the Callitrichidae tend to live in small multimalemultifemale groups, communally rear the young of one female, and exhibit a mating pattern characterized by female promiscuity but a breeding system that is functionally polyandrous. There is a significant correlation between the number of males and a group and the total number of surviving young. The possible adaptive advantages of this social organization are discussed. An erratum to this article is available at .     

Female social relationships in a captive group of Campbell's monkeys (Cercopithecus campbelli campbelli)

A study group of Campbell's monkeys (Cercopithecus c. campbelli) provided data on affiliative and agonistic relationships between females. Over a period of two years (involving 111 hr), we conducted observations of a captive group which had a composition similar to wild groups. We were able to identify a monitor-adjust social system with frequent affiliative interactions, directed gazing and avoidances rather than aggressive acts. We described long-term differentiated affiliative bonds: adult females interacting more often with some group mates than others, especially if they were relatives. Interactions between matrilines concerned essentially play and young adult females. We found a significant linear hierarchy of dominance with rare reversals and a stable intermatriline dominance. In contrast to other single-male groups, our adult male was socially integrated into the group although this may have been because of the housing conditions. Comparisons with the social organization of other captive and wild guenon groups are discussed.     

Genetic differentiation in sympatric wood ants, <Emphasis Type="Italic">Formica rufa</Emphasis> and <Emphasis Type="Italic">F. polyctena</Emphasis>

Summary Direct observations have suggested that the closely related wood ants Formica polyctena and F. rufa represent different social organizations, with high queen number in F. polyctena and a high frequency of monogynous nests in F. rufa. We examined social organization and genetic population structure in a setup where populations of the two species are sympatric and gene flow between the species is possible. Our aim was to compare social organization in the species, and study evolutionary relationships between them. The observed relatedness among colony workers suggested that the difference in the level of polygyny is quantitative rather than qualitative, with a higher queen number in F. polyctena. The observed difference in polygyny was not accompanied by a difference in spatial genetic differentiation which was weak in both species. The genetic distance between the species is consistent with limited interspecific gene flow. Identification of a few possible F. rufa migrants in F. polyctena populations suggests potential interspecific gene flow. Thus, reproductive isolation of the species may not be complete when they are sympatric.Received 14 March 2003; revised 10 October 2003; accepted 20 October 2003.     

Colony Membership, Division of Labor, and Genetic Relatedness Among Females of Colonies of Eustenogaster fraterna (Hymenoptera, Vespidae, Stenogastrinae)

To compare the social structure of primitively social wasps with that of communal breeding vertebrates, we used a new technique based on micro videocameras applied to the nest envelope to study the organization of behavior in Malaysian colonies of the stenogastrine wasp Eustenogaster fraterna. The reproductive division of labor in this species appears to be different from that reported so far in other species of Stenogastrinae: it is at a very primitive stage because the helpers work less hard and take fewer risks than the egg-layers. Nevertheless, the very low-risk tasks performed by the helpers (nest guarding and supply of abdominal secretion to the young larvae) are important for the colonies. Behavioral characters and ovarian development of the helpers suggest that females are only temporary helpers and that they wait to start their own production of offspring in the hope of inheriting the nest. Females of the same colony can be highly related, but in some colonies we found low-related individuals. The social organization of these wasps resembles that of vertebrate groups with helpers at the den, i.e., in the small number of individuals, the division of labor with limited reproductive inhibition, and the prolonged external work of the reproductive individuals. However, the main drive to sociality in these insects appears to be different, being based mainly on problems connected with short adult life and long immature brood development.     

Genetic similarity in long-eared owl communal winter roosts: a DNA fingerprinting study

The long-eared owl is a nocturnal predator which winters communally and breeds in the same areas in loose colonies during the spring. We tested the hypothesis that roosts, particularly stable roosts, are formed by close relatives, a condition under which group-related behaviours such as information sharing or helping at nest are more likely to be developed. DNA fingerprinting analysis was used to examine genetic similarity within and between two long-eared owl populations, one wintering in a traditional roost and the other in an unstable roost, and both breeding around their roosting sites. Although genetic similarity within roosts was higher than that between roosts, the difference was not significant. Observed genetic similarity within roosts was smaller than that reported in the bird species whose roosts work as information centres. On the other hand, the presence of some closely related individuals in the roost and behavioural observations suggest that co-operation between kin might have occurred, at least in one of the two study sites.     

A comparison of techniques for assessing dispersal behaviour in gundis: revealing dispersal patterns in the absence of observed dispersal behaviour

Knowledge of the dispersal status of group members is important to understanding how sociality may have evolved within a species. I assessed the effectiveness of four techniques for elucidating dispersal behaviour in a rock-dwelling rodent ( Ctenodactylus gundi ) with small group sizes (2–10 animals): genetic parentage assignment, haplotype data and kinship analyses, assignment testing, and F -statistics. The first two methods provided the greatest insight into gundi dispersal behaviour. Assignment testing and F -statistics proved of limited use for elucidating fine-scale dispersal, but could detect large-scale patterns despite low sex-biased dispersal intensity (1.9 : 1) because of moderate genetic differentiation among groups ( F _ST = 0.10). Findings are discussed in light of current dispersal theory. In general, gundi dispersal is plastic, and seems to be dependent on body weight (for males), group composition, and scale of analysis (total dispersal events recorded within the population were almost twice the immigration rate into the population). Most groups were comprised of a single matriline and one immigrant male. Immigrant rather than philopatric males bred with group females. Dispersal among groups was male-biased, but dispersal or philopatry could occur by either sex. During a drought, both sexes delayed dispersal and cooperative social units formed. Whether such behaviour resulted directly from the drought or not remains unclear, however, since comparative information was not available from nondrought years. Combining fine-scale analyses with information on large-scale patterns provided substantial insight into gundi dispersal behaviour despite the limited movement of animals during a drought, and may prove useful for elucidating dispersal behaviour in other social animals.     

Use of artificial arenas to predict the social organisation of halictine bees: Data for fourteen species from Chile

I studied the behavioural profiles of fourteen species of Chilean halictine bee using the circle tube apparatus. Interactions were classified as aggressive, avoidance or cooperative. One species, Corynura chloris, is believed to be semisocial and its behaviour was largely aggressive, Ruizantheda mutabilis is known to be communal and its behaviour was predominantly cooperative whereas Penapis toroi is a member of a subfamily from which only solitary behaviour is known and it primarily exhibited avoidance behaviours. As a result, I suggest that the relative frequency of these different behaviours may be useful in establishing the social organisation of species. Based upon comparisons of behavioural profiles, I predict the social organizations of the remaining species and suggest that at least some of the bees in the populations of Ruizantheda proxima, Caenohalictus dolator, Ca. species A and Pseudagapostemon pississi investigated exhibit communal behaviour; those of Co. patagonica and Co. herbsti likely have a reproductive division of labour, probably within semisocial societies, and that the populations of Co. corinogaster, Co. melanocladius, Ca. pygosinuatum, Ca. cuprellus and Lasioglossum aricense studied are probably solitary. Phylogenies suggest that solitary behaviour in Ca. pygosinuatum and Ca. cuprellus is reversed from communal behaviour and solitary behaviour in L. aricense may be a reversal from eusociality. The response “back and follow” is not indicative of dominance or cooperation as it correlated only with the frequency of avoidance interactions among the taxa studied. I discuss the utility of the circle tube apparatus in the identification of populations worthy of more detailed sociobiological investigation. Received 10 August 2005; revised 8 March 2006; accepted 21 March 2006.     

Male reproductive skew, paternal relatedness, and female social relationships

Female social relationships among primates are thought to be shaped by socio-ecological factors and phylogenetic constraints. We suggest that patterns of paternal relatedness among females influence measures of social tolerance that have been used to classify species into different social relationship categories. As kin support and kin preference have only been measured for matrilineal kin and related individuals exchange less aggression and have a higher conciliatory tendency, the observed low nepotism levels and high tolerance levels may be an artifact of hidden paternal relatedness among the nonkin category. Using comparative data on macaques, we investigate this hypothesis using male reproductive skew as a proxy for paternal relatedness. Within the limitations of the study we show that populations classified as being less nepotistic, and more tolerant exhibit higher levels of reproductive skew. This first result and the reasoning behind may motivate future students of social relationships to take paternal relatedness into consideration. Potential implications of this finding if repeated with larger samples include that variation in aspects of macaque social relationships may be explained without considering phylogeny or the strength of between-group contest competition for food.