Spider real estate wars: Wake up early

Big spiders in a colony get prime real estate day after day by spinning webs early, researchers suggest.

Timing plays a huge role in determining the web positions of the social orb weaver Metepeira incrassata, say Linda S. Rayor of Cornell University and George W. Uetz of the University of Cincinnati. They monitored colonies in Mexico, where hundreds of spiders rebuild their urban sprawl of closely spaced structures every day (SN: 5/8/99, p. 300: https://www.sciencenews.org/sn_arc99/5_8_99/bob2.htm).

Predators nab disproportionately more of the spiders in the slums at the colony margins, the researchers report in the May Animal Behaviour. “I had anticipated that the spiders would get up every morning and fight with each other to get to build in the safer core,” Rayor recalls.

The contests turned out to have more subtlety. The largest spiders, females with eggs, simply built much earlier—and in better locations—than small youngsters. If little ones tried to build early, big ones threatened them. When Rayor took big spiders out of a colony, “the little ones built their webs over an hour earlier because they weren’t getting hassled,” she says.

Rayor notes that not many people have studied how social animals space themselves and “how they wrestle for advantage without actually beating the tar out of each other.”

Susan Milius is the life sciences writer, covering organismal biology and evolution, and has a special passion for plants, fungi and invertebrates. She studied biology and English literature.