A Simpler Way to Organize Society: Response to a Risky Stimulus is Related to the Spatial Distribution of the Individuals Within a Spider Colonial Web

Abstract

Animals living in social groups often need to conduct certain tasks, such as prey capture or nest maintenance. We might expect individuals to specialize in these tasks, as specialization should increase efficiency and therefore group performance. In groups that vary in sex, morphology, or generation, these factors often determine task participation. However, in social groups where these factors are invariant, persistent individual differences in behavior may drive task specialization. We tested this prediction in groups of the social spider Anelosimus eximius, through experiments conducted on natural colonies in the field. We measured the response to a risky stimulus of individual spiders and then tested whether this predicted their location and/or activity when placed back in a colony. We found the more risk-prone individuals were more likely to be in the more exposed areas of the colony used for capturing prey. Irrespective of the risk-taking behavior, individuals rest and care for young in the protective region of the colony, while in the exposed area of the web individuals are more active and more likely to be walking. Therefore, individual’s responses to risk showed an influence on where an individual would settle within the colony but had no effect on its activity. Our results support previous work that suggests adult A. eximius do not specialize in tasks. Indirect pathways for individual traits, via differences in spatial location or activity levels, may help to explain variation among-individuals in task participation.