Tuesday, 4 June 2013

Big Brothers and Sisters Pay Off for Nature's Social Spiders

May 29, 2013 — The behavior of social spiders may settle debates over the benefits of older siblings. Cornell University researchers studying Australian social huntsman spiders discovered that younger siblings thrive when raised in nests with older siblings. Bigger brothers and sisters capture bigger, juicier prey, which they share with their younger siblings.

The researchers found that younger siblings weighed substantially more when they shared the prey of their elder brethren. Since smaller spiders eat relatively little, there is little to no cost to the older siblings. The study, published online in the journal Animal Behavior, describes how prey sharing can directly benefit spiders living as a group. Australian social huntsman spiders (Delena cancerides) are fairly common throughout the southern half of Australia, living as family groups with a single mother and multiple clutches of her offspring in retreats under the loose bark of dead trees.

"One of the most unusual things about Delena colonies is that there are siblings of a huge range of ages and sizes, in the colonies together at the same time," said Linda Rayor, a Cornell entomologist and co-author of the study. "It's common to have tiny spiderlings mingling with older siblings that are almost a year old. So what is totally cool about Delena is that mix of siblings of different ages and how they interact around prey brought into their retreat." Rayor describes such social sharing in a Cornell video.

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