Population differences in the aggregation and collective foraging behavior of fragmented social spider colonies

Long-term interactions among individuals are a hallmark of animal societies, but groups rarely remain entirely stable over time. Individuals die or emigrate, or groups become spatially fragmented. Group fragmentation can alter the phenotypic composition of subgroups by separating well-connected individuals or altering sex ratios, which may alter the execution of collective behaviors. Over 10 days, we measured the aggregation behavior and collective prey capture of experimentally fragmented social spider (Stegodyphus dumicola) colonies collected from different populations in South Africa and Namibia. Colonies were fragmented for 4 weeks, after which subgroups were allowed to aggregate into a single group over time in a shared novel environment. Namibian colonies aggregated more rapidly than South African colonies. Across both populations, colonies containing individuals with higher average boldness values (faster recovery time after an antagonistic stimulus) attacked prey stimuli with more participants. However, bolder colonies from South Africa attacked prey stimuli faster, whereas attack latency in Namibian colonies was unaffected by colony boldness. These data suggest that fragmentation events, which are a common phenomenon in this species and other animal societies, can influence how individuals interact to accomplish collective tasks. Further, collective behavior and group fusion after fragmentation events can differ among groups from different populations.

Automated summary

Long-term interactions in animal societies are not stable due to individuals dying or groups becoming fragmented. This study on social spiders found that fragmentation events can influence how individuals interact and accomplish collective tasks, and the behavior and fusion after fragmentation can differ among groups from different populations. The results suggest that group stability and composition play a crucial role in collective behavior.