Spiders are largely silent to human ears because they lack lungs or vocal cords, meaning they cannot vocalize in the typical sense. Instead, their world is dominated by mechanical signals used to interact with their environment. These signals, often imperceptible to us, form a sophisticated communication system for the arachnids.
The Primary Mode of Communication
For most spiders, the primary way they communicate and perceive the world is not through airborne sound, but through vibrations transmitted through a surface, known as seismic or substrate-borne vibrations. The web, the ground, or even the surface of water acts as a communication medium, transmitting subtle ripples that carry information. These signals travel in the low-frequency range, often between 1 to 300 Hertz.
Spiders are adapted to detect these mechanical messages using specialized sensory organs called slit sensilla. These small, groove-like structures are found on their legs and deform when exposed to even the slightest vibrations, allowing the spider to decode the meaning of the movements. A web-building spider relies on these vibrations to detect potential meals, approaching predators, or signaling mates.
Rare Instances of Airborne Sound Production
While most spider communication is vibrational, some species produce sounds audible to humans, usually for defense or courtship. The most common intentional sound is stridulation, which involves rubbing two specialized, rigid body parts together, similar to a cricket chirping. This process uses a “scraper” moving across a ridged “file” surface to create a hissing or chirping noise.
Many tarantulas, such as the Goliath bird-eater, use stridulation as a defensive warning by rubbing bristles on their legs together, creating a loud hiss audible up to 15 feet away. Other spiders, including wolf spiders, use a percussive signal known as drumming. They tap their legs or pedipalps against a surface to create rhythmic patterns. Male wolf spiders and jumping spiders use these complex drumming routines during courtship, with the female sensing the rhythm through the substrate. These audible sounds are often very faint, however, and require close proximity to be perceived by a person.
Incidental Sounds from Spider Movement
Many sounds people associate with spiders are not intentional communication signals but secondary noises resulting from movement or activity. Large, heavy-bodied spiders, particularly tarantulas, can create an audible scuffling noise as they walk across hard floors or wood surfaces. This sound is simply the friction and impact of their eight legs against the substrate and is not a deliberate attempt to signal.
Sounds also frequently arise from the web itself when insect prey struggles against the sticky silk strands. The rustling or buzzing of a trapped fly is an incidental sound that travels along the silk, alerting the spider to its dinner. Furthermore, the act of a spider manipulating its silk, such as cutting or pulling a strand, can produce faint, high-frequency sounds.