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Schwab Christine | Fellow Postdoctoral
2009-11-15 - 2011-11-14 | Research area: Cognition and Sociality
Social Networks in Corvids: Investigating Structural and Functional Patterns of Social Systems
My interest within the proposed project concentrates on the evolution of social behaviour by investigating structural and functional aspects of jackdaw, Corvus monedula, and raven, Corvus corax, social systems. I will employ a theoretical approach and methods that originated in mathematical graph theory and are new and innovative in animal behaviour research: social network theory and social network analysis (SNA). The project comprises two objectives: first, to generate and analyse networks in these two species and to investigate their comparability and changes over time and second, to experimentally address the question which social network influences transmission of information and access to resources within the group. Data on social interactions already exist. They consist of two years of observations on one captive colony each, one year on a wild jackdaw colony, and data on wild ravens are currently collected. SNA has several important advantages for the proposed project: 1) It provides mathematical evidence for the composition of networks, contrasting former a priori classifications by the human observer. 2) It allows a more detailed analysis of the social fine structure of groups by going beyond categorization (by sex, age, kinship, mating system, etc.). 3) It provides several analytical measures to allocate subjects certain structural positions within the group, such as centered, marginal or bridging positions. 4) Results of SNA yield nondimensional values that allow comparisons between groups, populations, or species. Objective 1: Analysis of social interactions is expected to result in 4 networks (sociopositive, spatial association, agonistic, defensive) that differ distinctively with regard to several SNA measures. Each of these networks will be analysed in three time periods, reflecting different periods in the birds` annual cycle. Comparisons of networks between periods, contexts (in the wild and in captivity) and species will show how networks change over time and will provide better insight into the social structure (sensu Hinde 1976) of jackdaw and raven colonies. Objective 2: Here I will investigate the functional value individuals can draw from their social networks in two different contexts. First, two antithetic hypotheses will be tested regarding propagation of information within a group. Hypothesis A is commonly found in the literature: spatial proximity/affiliation between individuals enhances social learning and, therefore, information transmission within groups should follow affiliation patterns between group members. Hypothesis B stems from human sociology: weak ties are important for information transmission (tie = sociopositive and symmetric). Therefore, information transmission should follow agonistic patterns between group members. In two experiments 18 jackdaws will be tested in a group setting. Determination of the order of individuals succesfully manipulating a testing apparatus (experiment 1: several apparatuses present, non-monopolizable food context) and getting acces to the testing apparatus (exeriment 2: only one apparatus present, monopolizable food context) will then be compared with the structure of the birds` networks to assess which network influences the pattern of information transmission (experiment 1) and which network regulates access to limited resources (experiment 2). Together results will show how individuals benefit from respective networks.