Spiders seen weaving ‘scarecrows’ of themselves to fool predators

The findings mark the first instance of any creature creating “scarecrow” versions to escape predators, researchers said.

These orb-weaving spiders belong to the genus Cyclosa and are found in the dense rainforests of the Philippines and Peru.

They have been seen making decorations resembling much larger and more dangerous spiders out of silk and natural materials such a prey carcasses, leaves and plant matter.

Sometimes these decoys, often arranged at the centre of the web, may be up to 10 times as large as their creators, according to the new study published in the journal Ecology and Evolution.

The Cyclosa spiders also shake their webs to move their decoys, known as stabilimenta, and scare off potential predators.

“Here, we provide the first formal scientific record of Cyclosa species from two continents that create stabilimenta visually resembling the shape of a larger spider,” researchers wrote in the study.

“The decoys created by our Cyclosa species are not just larger, but they are shaped to resemble a potential threat or an undesirable prey item, potentially providing a more effective deterrent against predators like damselflies.”

They complete the most critical part of their defence when visual predators are not active

The Peruvian spider was observed constructing its decoys in darkness after the sun set, completing the rest of the web closer to dawn. Researchers suspect this behaviour is evolutionarily optimised.

“This strategy allows them to complete the most critical part of their defence when visual predators are not active,” they wrote.

“The spiders can then rest and complete the finer parts of the web in the pre-dawn hours, ensuring that their snare is ready for prey capture at first light.

“This would minimise the time the spiders are exposed without their primary defence during daylight hours.”

However, the researchers were unclear about what forces drove these particular populations or species to evolve such complex “spider-like decoys”.

“Perhaps there is particularly strong selection from predation within both of these groups that has resulted in increasingly complex visual defence,” the scientists wrote.

They suspect future experiments comparing the survival rates of spiders with different decoy sizes and web decorations could help test the protective function.