Visual antipredator effects of web flexing in an orb web spider, with special reference to web decorations

Luis E. Robledo-Ospina, Nathan I. Morehouse, Federico Escobar, Horacio Tapia-McClung, Ajay Narendra, Dinesh Rao*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Some visual antipredator strategies involve the rapid movement of highly contrasting body patterns to frighten or confuse the predator. Bright body colouration, however, can also be detected by potential predators and used as a cue. Among spiders, Argiope spp. are usually brightly coloured but they are not a common item in the diet of araneophagic wasps. When disturbed, Argiope executes a web-flexing behaviour in which they move rapidly and may be perceived as if they move backwards and towards an observer in front of the web. We studied the mechanisms underlying web-flexing behaviour as a defensive strategy. Using multispectral images and high-speed videos with deep-learning-based tracking techniques, we evaluated body colouration, body pattern, and spider kinematics from the perspective of a potential wasp predator. We show that the spider’s abdomen is conspicuous, with a disruptive colouration pattern. We found that the body outline of spiders with web decorations was harder to detect when compared to spiders without decorations. The abdomen was also the body part that moved fastest, and its motion was composed mainly of translational (vertical) vectors in the potential predator’s optical flow. In addition, with high contrast colouration, the spider’s movement might be perceived as a sudden change in body size (looming effect) as perceived by the predator. These effects alongside the other visual cues may confuse potential wasp predators by breaking the spider body outline and affecting the wasp’s flight manoeuvre, thereby deterring the wasp from executing the final attack.

Original languageEnglish
Article number23
Pages (from-to)1-13
Number of pages13
JournalScience of Nature
Volume110
Issue number3
Early online date23 May 2023
DOIs
Publication statusPublished - Jun 2023

Keywords

  • Deimatic displays
  • High-contrast visual cues
  • Secondary defensive strategies
  • Visual ecology

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