Size Matters in Kalahari Desert Social Spider Colonies

Posted on April 27, 2014

Scientists say size and body condition help determine the task a Kalahari social spider will perform within a colony. The spiders live in colonies of up to 2,000 members. Carl Keiser and Devin Jones of the University of Pittsburgh made the discovery after observing the spiders in the lab.

Stegodyphus dumicola spiders live in colonies in thorn trees in the arid parts of southwestern Africa. They build large webs consisting of dense communal living areas and a two-dimensional capture web. The scientists carefully observed the spiders to see how individual spiders were involved in tasks such as attacks, web building or web repairing.

The researchers found that body size and body condition influence the chances that an individual spider will perform a range of tasks needed to maintain the colony. Spiders with smaller bodies are more likely to help with web building and maintenance. Those with lower body condition are more likely to be busy with foraging. Individuals' tendency to engage in prey capture was not associated with either their behavioral traits or body size. The researchers also noticed different colonies had variation in behavior, a colony-level personality. Some colonies were found to be more aggressive than others.

Keiser says in a statement, "The results are intriguing because this trait variation and its resulting task differentiation gives rise to a cooperative breeding society composed of highly related, inbred individuals. The spiders are of nearly identical age and develop together in synchrony. Our findings differ from the once conventional reasoning among social spider researchers that social spider societies are homogenous and egalitarian."

The research was published here in the journal, Behavioral Ecology and Sociobiology.

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