Tuesday, November 02, 2021

It's not just humans: Some spiders also suffer from arachnophobia, study suggests

Sorry arachnophobes, it looks like you have more in common with your worst nightmare than you might think.
© Provided by National Post A jumping spider is seen lounging on a tree. Researchers used baby jumping spiders to test their predator-recognition instinct with other spiders.

A new study has found that some species of spiders may also suffer from ‘arachno-arachnophobia’, otherwise known as a fear of other, larger members of their kind.
The study, published by the British Ecological Society in their journal, Functional Ecology, examined the behavioural responses of baby jumping spiders to predator and non-predator objects to determine their predator-recognition instincts.

“Jumping spiders are absolutely amazing because they have this incredible eyesight. And they can see almost as good as we do, so they pay attention to detail,” Daniella Roessler, the study’s lead researcher, told NPR on Wednesday.

As part of the study, Roessler and her team presented the baby spiders with a number of objects: first, a spheroid 3D printed model as the experiment control, followed by a 3D printed spider and an actual larger, dead spider, all matched in size.


They then observed the jumping spider to see whether it would be able to detect which of the objects are potential predators, without relying on the objects to move.

A video recording the spiders’ reactions first shows a baby spider appearing to assess the black 3D spheroid model. With almost no hesitation, the spider scuttles to and jumps over on the platform on which the model stands and climbs over the model, indicating no fear of the object.

However when confronted with a 3D printed black spider, fitted with frontal eye features, the baby spider appeared to freeze, slowly move to the side and then decisively turn away and jump off in the opposite direction.

The same sphere, without the frontal eye features, provoked a slightly bolder reaction in the baby spider — it moved forward on its platform, as if to assess the large object standing in front of it, but within seconds turned in the opposite direction away from the object.

The baby spider was then presented with multiple species of dead jumping spiders — the marpissa muscosa and the phidippus audax .

Researchers noted that the baby was much more fearful of the species that looked like itself — the brown marpissa muscosa — and refused to come any closer to the dead specimen, instead freezing and slowly backing away.

“There’s a lot of assessment of the risk in this moment, so they assess how big is that thing? How quick could it get to me?” Roessler explained to NPR. “And then also knowing that motion really triggers what jumping spiders perceive, like, moving away in this choppy fashion and really slowly maybe is also a strategy of not getting the attention from the predator.”

Researchers determined that the jumping spiders can “indeed, identify predator objects in the absence of motion.”

“Spiders ran away after looking at predator objects, while they showed no escape behaviour towards the control,” they wrote in the study.

The presence of eyes, they said, acted as an important cue, but the spiders appeared to look at multiple features rather than one, to assess predator risk.

Using baby spiders in the study, researchers added, also enabled them to ascertain that the predator-recognition instinct is not a honed response, but rather, an innate behaviour from birth.

Which means, you could use your favourite spider decorations for Halloween to keep the some of the real ones away — just use the ones without the round eyes, Roessler advised.

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