Joro spiders are shy, not aggressive

Despite their formidable appearance, the giant yellow and blue-black spiders found in the Southeastern U.S. owe their survival to an unexpected trait: They are remarkably timid.

A recent study conducted by the University of Georgia has revealed that the Jorō (Joro) spider may be the most bashful spider ever documented.

“Many people believe that this spider poses a threat to other species due to its aggression and ability to outcompete native spiders,” stated Andy Davis, the lead author of the study and a research scientist at UGA’s Odum School of Ecology. “Therefore, we aimed to understand the personality of these spiders and determine if they exhibit such aggression.”

Surprisingly, the study found that Joro spiders are far from aggressive.

The researchers examined the responses of over 450 spiders from ten different species when subjected to a brief and harmless disturbance. While most spiders froze for less than a minute before returning to their normal activities, the Joro spiders remained motionless for over an hour.

“They essentially shut down and wait for the disturbance to dissipate,” explained Davis. “Our research demonstrates that these spiders are more afraid of humans than the other way around.”

In fact, Joro spiders are relatively harmless to both people and pets. They rarely bite unless they are cornered. Even if a Joro spider were to bite, their fangs are typically too small to break the skin.

Therefore, despite their appearance, Joro spiders are not the aggressive predators they might be perceived to be.

Most spiders begin moving quickly after stress, Joros remain immobile for 60-plus minutes

To observe how the spiders react to stress, the scientists utilized a turkey baster to deliver two gentle puffs of air onto individual spiders. This minor disruption prompted the spiders to enter a state of complete stillness, essentially “freezing.”

The study encompassed more than 30 garden spiders, banded garden spiders, and marbled orb weavers. Additionally, the researchers analyzed data from previously published papers, which examined the response of 389 spiders from five other species.

Typically, all these spiders resumed their movements after an average of about one and a half minutes of immobility.

In stark contrast, the Joro spiders remained completely frozen, devoid of any body or leg movement, for well over an hour in most instances.

Interestingly, the only other spider species to exhibit a similarly prolonged reaction was the Joro spider’s relative, the golden silk spider. Scientifically known as Trichonephila clavipes, the golden silk spider belongs to the same genus as the Joro spider.

Joros may be invasive, but they’re not aggressive

The East Asian Joro spider, scientifically known as Trichonephila clavata, made its initial appearance in Georgia around 2013. Originating from Japan, Korea, Taiwan, and China, it is believed that the species hitchhiked to the United States through shipping containers.

Since its arrival, the Joro spider has rapidly proliferated throughout Georgia and much of the Southeast. The population of Joro spiders now easily reaches into the millions, and their expansion shows little sign of being halted.

In fact, previous research conducted by Davis indicated that these invasive spiders could potentially extend their range even beyond their current habitats and spread across the majority of the Eastern Seaboard.

The common assumption is that “invasive” and “aggressive” go hand in hand. However, the findings of this study aim to alleviate concerns about the Joro spiders. Amitesh Anerao, co-author of the study and an undergraduate researcher at the university, expressed, “Initially, people were alarmed about the Joro spiders, but perhaps this research can help assuage their fears.”

Joro spiders built to withstand human activity

Joro spiders have been observed in areas where native Georgia spiders are not typically found, such as building their distinctive golden webs between power lines, on top of stoplights, and even above gas station pumps—locations that are far from serene.

The researchers propose that the Joro spiders’ timid nature may enable them to better withstand the constant onslaught of noise, vibrations, and visual stimuli prevalent in urban environments. Their extended freezing response when startled could aid in conserving their energy.

The remarkable speed at which Joro spiders have spread raises questions about how such a mild-mannered creature could achieve such widespread distribution. Davis suggests that their rapid expansion is likely due to their exceptional reproductive capacity rather than displacing or evicting native spiders from their webs.

While those with arachnophobia may find solace in the Joro spiders’ docile and non-aggressive temperament, it appears that they are here to stay.

“They have adapted so well to coexisting with humans,” remarked Anerao, indicating that the spiders are unlikely to disappear anytime soon.

The study documenting these findings has been published in the journal Arthropoda.

Source: University of Georgia

Leave a Comment