A University of Georgia study observed that Joro spiders tend to freeze for long stretches when a human appears, a behavior interpreted as fear rather than aggression. The researchers noted that this freezing response signals a defensive stance, not a predatory intent, and reflects the spider’s sensitivity to potential threats in the environment. The finding provides insight into how these spiders react under sudden human presence and helps explain why some people perceive them as dangerous.
Spiders known as Joro or Trichonephila clavata are an invasive species in the United States. They originate from eastern Asia and have established populations in several states. These arthropods are large, with bodies and webs that can reach up to about 3 centimeters in diameter. Their conspicuous coloring includes bright yellow bands that make them stand out in the landscape. For many Americans unaccustomed to these arrival species, the sight of such large, vividly marked spiders can provoke fear, reinforcing the belief that they are inherently aggressive.
To assess whether this fear is rational, a team led by Andy Davis conducted controlled experiments on 450 spiders spanning 10 different species. In the trials, the spiders were gently disturbed by a jet of air from a syringe to simulate a mild intrusion. The researchers observed how the spiders responded to this disturbance, comparing the reactions across species. The Joro spiders showed a striking difference: they remained motionless for more than an hour in many cases, whereas most other species stopped briefly before resuming their normal activities.
According to the scientists, this tendency to “shut down” represents a strategy to wait out the disturbance rather than escalate it. The study demonstrates that these spiders fear human presence more than many people fear them, highlighting a mismatch between perceived danger and actual threat in daily encounters.
Despite the dramatic appearance and large size of Joro spiders, they pose little danger to people. They bite only as a last resort when cornered, and their fangs and venom are not capable of piercing unbroken adult skin. In everyday settings, these spiders are not a significant threat, and most encounters end without incident. Observers are advised to give them space and avoid handling them, which reduces any chance of a defensive bite. The overall risk remains low, and awareness is the best defense when these spiders are found in homes or gardens.