Scientists from the Australian National University (ANU) and the University of Florida have revealed a remarkable survival strategy used by two tiny orb-weaving spiders: they build giant, lifelike decoys of themselves to scare off predators. 

The spiders — found in Peru and the Philippines — construct webs that double as “theatres of deception” to trick would-be attackers, ANU tropical ecologist Dr George Olah, the study’s lead author, says.

“They don’t just decorate their webs — they meticulously arrange detritus, prey carcasses and silk into a structure that’s not only larger than their own body, but clearly resembles the silhouette of a bigger, menacing spider,” Dr Olah said. 

Researchers believe the “decoy spider” may mimic a larger predator that birds and lizards instinctively avoid, while also creating a diversion to draw attention away from the smaller, real spider.

“This behaviour is not just a quirky biological observation; it illustrates a fundamental evolutionary trade-off in the spider world,” co-author Dr Lawrence Reeves from the University of Florida said. 

“Unlike many orb-weavers that build a physical retreat to hide, these Cyclosa species appear to invest their time and resources into building an expendable visual defence instead.” 

The spiders’ remarkable behaviour was recently captured on film for the multi-Emmy Award-winning documentary The Secret Lives of Animals. 

Dr Olah said further studies could explore whether spiders that build these decoys have higher survival rates than those that don’t.

“It might be the case that particularly strong selection within both these groups has resulted in them developing an increasingly complex visual defence,” Dr Olah said. 

The findings are published in Ecology and Evolution.