Inter-and intra-individual behavioral variability during agonistic interactions of the funnel-web spider, agelenopsis aperta: do spiders have individual personalities?

Although agonistic (fighting) behavior has been studied extensively in several species of spiders using modern ethological techniques and statistical analysis, past studies were not designed to allow a proper analysis of behavioral variability in terms of inter- and intra-individual components. Such an analysis is important for an understanding of variability among individuals within a population. I have examined the extent to which the agonistic behavior of individual Agelenopsis aperta (Gertsch) is unique and repeatable. Data collected from induced contests between female A. aperta generated at natural sites in the New Mexico desert and in a more controlled laboratory setting suggested that 36% of individuals in my field sample and 13% of individuals in my laboratory sample exhibited behavior that was both repeatable and distinct from other individuals. For two variables examined for repeatability using the coefficient of intraclass correlation, the intra-individual (among contest) component of variability was found to be much greater than the inter-individual component for both the field and laboratory data sets. There was no evidence to support the existence of any "trends" in the data. Individuals did not appear to fit along any qualitative spectrum, such as aggressiveness or fear, nor did such a spectrum appear in correlation with either relative weight or contest experience (ordinal contest number).