Socialization processes in primates: use of multivariate analyses II-Influence of sex on social development of captive rhesus monkeys.

In a previous study, we demonstrated the importance of social interactions in the development of non-human primate infants. These results confirmed the social network concept. According to this concept, it is assumed that socialization processes would differ in various social environments. However, much variability remained to be explained. In the present study we investigated especially the influence of infants' gender on socialization processes. In relation to the previous results, the influence was tested within groups having the same social structure. At the Wisconsin Regional Primate Research Center, four mother-peer groups of rhesus macaques (Macaca mulatta) were studied. Therefore no adult male model was available to infants. Twenty infants, including eight males, eight females and four prenatally DES-treated females, were the subjects of this study. We considered six comprehensive developmental parameters to account for the two main socialization processses, the acquisition of the social behavioral repertoire and the establishment of a network of social relationships. We analyzed the variability of these parameters using a new multivariate technique previously described in a companion paper. This new technique is derived from the Principal Components Analysis and Multivariate Analyses of Variance. The model used in this analysis included two intrinsic features of infants, sex and age and two variables related to the social organization of the groups, mother's rank and social group. This 4-variable-model significantly accounted for most of the variability of the developmental parameters. The results showed that the social group and the infant's sex were the most influential variables when infants initiated interactions: male and DES female infants displayed a greater behavioral diversity than non-treated female infants. When infants were recipients in interactions, social organization variables (social group and mother's rank, respectively) had the greatest influence on the socialization processes while infants' gender was less influential. In this case the effect of sex was confounded with the social group effect; male infants then differed from both kind of female infants in being looked at more frequently, in being contacted by a larger variety of partners and in receiving a greater variety of social behaviors. This new example of applying multivariate methods to the study of individual social development confirms the potential of this method to provide new insights into behavioral development.

Socialization processes in primates: Use of multivariate analyses. I: Application to social development of captive mangabeys.

We hypothesized that, within a primate group, socialization processes are influenced by each group member behaving according to his own social network. Therefore socialization processes would differ in various social environments. In this study, we considered two main socialization processes, the acquisition of a social behavioral repertoire and the development of a network of social relationships, and consequently defined six comprehensive developmental parameters. We analyzed the variability of these parameters using a new multifactorial method, the Principal Components Analysis with Instrumental Variable, PCAIV, derived from the Principal Components Analysis and Multivariate Analyses of Variance. This technique allowed us to jointly represent the influence of the independent variables and the complex relationships between the six dependent variables. The study of the social ontogeny of eight infant mangabeys (Cercocebus albigena), reared in three different social environments, served as an illustration of the use of the new multivariate analysis. A 3-variable-model (age, social environment and sex) significantly explained the variability of the developmental parameters. The results confirmed the importance of social interactions in non-human primate infants' development. The application of multivariate methods to the study of individual social development looks promising for future research.

Introducing anthropomorphism, discontinuities and anecdotes to question them.

Recourse to anthropomorphism, folk psychology, or discontinuist thought, in order to take into account the richness of animal cognitive processes and of their evolution, is of some heuristic value. However, in the absence of recognised criteria allowing the hypothesised behavioural discontinuities between species to be tested and alternative interpretations of anecdotal reports to be selected, there is considerable risk that these alternatives will be ideological rather than scientific. A 'clinical analysis' of this anthropomorphism and discontinuist 'symptom' allows us to unravel its ideological aspect, namely the wishful thinking and the 'egomorphism' of a subject projecting a wishful representation of himself onto one who is not ego, and in turn to investigate its heuristic value in ethnological, psychopathological or animal behavioural studies. This analysis leads us to propose some tools:

Fruit characters as a basis of fruit choice and seed dispersal in a tropical forest vertebrate community.

Interactions between a large community of vertebrate frugivore-granivores (including 7 species of large canopy birds, 19 species of rodents, 7 species of ruminants, and 6 species of monkeys), and 122 fruit species they consume, were studied for a year in a tropical rainforest in Gabon.The results show how morphological characters of fruits are involved in the choice and partitioning of the available fruit spectrum among consumer taxa. Despite an outstanding lack of specificity between fruit and consumer species, consideration of simple morphological traits of fruits reveals broad character syndromes associated with different consumer taxa. Competition between distantly related taxa that feed at the same height is far more important than has been previously supposed. The results also suggest how fruit characters could have evolved under consumer pressure as a result of consumer roles as dispersers or seed predators. Our analyses of dispersal syndromes show that fruit species partitioning occurs more between mammal taxa than between mammals and birds. There is thus a bird-monkey syndrome and a ruminant-rodent-elephant syndrome. The bird-monkey syndrome includes fruit species on which there is no pre-dispersal seed predation. These fruits (berries and drupes) are brightly colored, have a succulent pulp or arillate seeds, and no protective seed cover. The ruminant-rodent-elephant syndrome includes species for which there is pre-dispersal predation. These fruits (all drupes) are large, dull-colored, and have a dry fibrous flesh and well-protected seeds.