Evidence of bird dropping masquerading by a spider to avoid predators

Area of Science:

• Ecology
• Animal Behavior
• Evolutionary Biology

Background:

• Many species employ masquerading (mimicking inanimate objects) for predator avoidance.
• The orb-web spider Cyclosa ginnaga exhibits a silver body and adds a white, discoid silk decoration to its web.

Purpose of the Study:

• To investigate if Cyclosa ginnaga's body coloration and web decoration combine to form a bird dropping masquerade.
• To determine if this masquerade reduces predation risk for the spider.

Main Methods:

• Spectral reflectance of spider bodies, web decorations, and bird droppings were measured in natural conditions.
• Predatory attacks on spiders with experimentally altered body/decoration coloration were monitored.

Main Results:

• The coloration of C. ginnaga's body and web decorations were spectrally indistinguishable from bird droppings to hymenopteran predators.
• Spiders with blackened decorations experienced significantly higher predation rates, indicating the decoration's crucial role.

Conclusions:

• The combined coloration of Cyclosa ginnaga's body and its web decoration effectively mimics bird droppings.
• This bird dropping masquerade is a key anti-predator strategy that reduces the spider's probability of predation.