Featured Image Caption: Palpimanus spiders produce a buzz similar to a wasp by rubbing their front appendages across their mouthparts (Source: “Palpimanus gibbulus” by fturmog is licensed under CC BY-NC-SA 2.0).
Reference: Pekár, S., García, L. F., & Bulbert, M. W. (2020). Spiders mimic the acoustic signaling of mutillid wasps to avoid predation: Startle signaling or Batesian mimicry? Animal behaviour, 170, 157-166. https://doi.org/10.1016/j.anbehav.2020.10.015
As children, we learn by copying the actions of the people around us. Maybe you pretended to vacuum after watching a parent vacuum. Maybe you repeated an unsavory phrase that you heard a family member say. Sometimes animals copy other animals. For example, monarch butterflies are colored bright orange to inform predators that they are toxic if eaten. Although entirely harmless, Viceroy butterflies look precisely like monarch butterflies and use their coloration to avoid being a snack. Most animals have learned to avoid the dangerous monarch and its harmless look-a-like, the viceroy. Animals usually mimic the appearance of other animals. It’s not very often that animals imitate the sounds of other animals.
Imagine a hot, humid night in the Mediterranean when hungry geckos emerge to search for their next meals. These geckos are not usually picky about their food – juicy spiders, moths, or crickets are sure to satisfy. However, the wasp is an unwelcome meal, for its potent sting will ruin any animal’s appetite. The familiar buzz from the wasp is a cue to the gecko to avoid an attack. The gecko continues with its hunt until it comes across a more appetizing spider. The gecko lunges and scoops up his tasty treat, only to be met with a familiar buzzing sound. Not wanting to be stung, the gecko releases the spider and continues with the search. The spider walks away unharmed. How did the gecko know to drop the spider if most animals use visual mimicry and spiders do not look like wasps? This spider, Palpimanus gibbulus, has evolved to mimic the sounds of a wasp to avoid being eaten.
What’s the Buzz?
Animals mimicking the sounds of other animals are extremely rare. In fact, the wasp-like buzz produced by Palpimanus spiders is the first confirmed case of spiders mimicking sounds as a predator defense. Many animals have learned to associate buzzing with things that sting. I even feel my blood pressure rise a little when I hear a buzzing wasp nearby. Palpimanus spiders produce a buzzing sound by rubbing their front appendages against their mouthparts. All Palpimanus spiders will make this sound when disturbed, especially by potential predators like geckos and huntsman spiders. Spiders are vital members of the food chain, acting as both prey and predators. As part of their role as predators, spiders help to keep pest populations under control. Researchers at universities in the Czech Republic, Uruguay, and Australia wanted to determine if Palpimanus spiders imitate the buzz of wasps to avoid being prey.
Stano Pekár and his colleagues collected spiders and geckos and wasps (oh my!) from Southern Spain and Portugal. The researchers first recorded and compared the buzzes of Palpimanus spiders and the four wasp species. Geckos and huntsman spiders are natural predators of spiders. The researcher observed these predators’ responses to silent wolf spiders, silent Palpimanus spiders, buzzing Palpimanus spiders, and buzzing wasps.
Spider See Spider Do
The Palpimanus spiders sounded similar to the wasp species but were three to five times quieter than the wasps (hear for yourself!). The huntsman spider never attacked buzzing wasps, always ate silent wolf spiders, and lunged at buzzing Palpimanus spiders about a third of the time. On the other hand, geckos always grabbed buzzing Palpimanus spiders but consistently spat them out. Even though geckos handled buzzing Palpimanus spiders longer, they survived the attacks at similar rates to wasps. The spiders endured a few chomps from the geckos, thanks to their very thick outer layer.
Most spiders are harmless to both humans and predators, but the Palpimanus spider has evolved to sound dangerous by mimicking wasps’ sounds. Spiders are crucial for most ecosystems for their essential role as both predator and prey. They control pest populations that threaten crop production and spread diseases by eating about 800 million tons of these pests from our yards, fields, and natural spaces each year. Studies like these continue to unveil how predators and prey interact and evolve different strategies to survive. Biologists have found very few examples of sound copying as a defense, compared to visual copying. For example, non-toxic moths may imitate the ultrasonic calls that toxic moths use to inform bats they are poisonous. Harmless viper-like snakes have evolved to hiss like harmful vipers. Biologists are continuing to discover cases of sound copying. Who knew spiders could create this much buzz!