Spiders are not associated with sound perception because they do not possess eardrums. To sense movement, spiders use the tiny hairs on their legs to sense vibration (and spiders can ‘sense’ variations in vibration when different objects become caught in their webs). However, even without eardrums, jumping spiders can detect distant airborne sounds, according to some new research.
Some types of spider can pick up sounds from relatively long distances (up to 10 feet), according to Dr. Ronald Hoy, who is a neurobiologist at Cornell University.
Dr. Hoy has been studying a jumping spider called Phidippus audax (the North American spider is commonly referred to as the daring jumping spider, or bold jumping spider). These spiders have been known to jump from 10 to 50 times their own body length by suddenly increasing the blood pressure in the third or fourth pair of legs.
For the research, Hoy’s researchers placed micro-sized electrodes into the brains of the spiders. The researchers then made various sounds at various distances to see how the spider reacted. Reaction was assessed by determining whether neurons in the brain of the spider reacted.
The outcome, Science News reports, was that spiders can perceive sounds, even those that are relatively quiet, such as people talking. In a typical house this would mean a spider could detect people talking on the other side of a room.
In terms of pitch (which is measured in hertz), jumping spiders can hear sounds between 70 and 200 hertz. Humans typically hear sounds best between 500 hertz and one kilohertz, although many people can detect sounds outside of this range.
To test whether a spider can differentiate sounds, the researchers ran further studies, this time simulating the sound of a predatory wasp (a type of droning sound). In this case the spider reacted as if it was under threat. In the natural environment, such wasps carry off jumping spiders and immobilize them with venom.
The findings are published in the journal Current Biology. The research is titled “Airborne acoustic perception by a jumping spider.”
In related news, some species of spider tune their webs to different frequencies in order to catch prey and to attract partners, according to a new study.
