Invasive Joro spiders don’t mind city living

A new UGA study found the invasive Joro spider isn't particularly phased by the vibrations and noise of city living. (Credit: Dorothy Kozlowski/U. Georgia)

A new study has found clues as to why the invasive orb-weaving Joro spider is so successful at spreading to new locations: it’s surprisingly tolerant of vibrations and noise common in urban landscapes.

The Jorō (Joro) spider was first spotted in Georgia around 2013 and has since been spotted across the state Georgia and the Southeast.

In the new study, published in the journal Arthropoda, researchers examined how Joro spiders can live next to busy roads, which are notably stressful environments for many animals.

They found that while Joro spiders near busier roads are somewhat less likely to attack simulated prey, they don’t seem to be hurting for it and clock in at about the same weight as their counterparts in less busy locations. That suggests the species can successfully compensate for its human-dominated landscape.

“If you’re a spider, you rely on vibrations to do your job and catch bugs,” says Andy Davis, corresponding author of the study and a research scientist in the University of Georgia’s Odum School of Ecology. “But these Joro webs are everywhere in the fall, including right next to busy roads, and the spiders seem to be able to make a living there. For some reason, these spiders seem urban tolerant.”

Joro spiders ‘are here to stay’

Joro spiders are regularly spotted in areas that native Georgia spiders don’t inhabit. They build their golden webs between powerlines, on top of stoplights and even above the pumps at local gas stations—none of which are particularly peaceful spots. That is what drew Davis and his team to study their behavior near roadsides.

Davis and a team of undergraduates from the Odum School used a tuning fork to simulate the vibrations caused by prey when caught in a spider’s web and then watched if the spiders attacked. Of the more than 350 trials, Joro spiders attacked the simulated prey 59% of the time.

The spiders in webs near busy roads attacked about half the time while those near lower traffic areas pounced 65% of the time. Despite that slight difference, it doesn’t look like it’s affecting the spiders’ body mass or health.

“It looks like Joro spiders are not going to shy away from building a web under a stoplight or an area where you wouldn’t imagine a spider to be,” says coauthor Alexa Shultz, a third-year ecology student. “I don’t know how happy people are going to be about it, but I think the spiders are here to stay.” Her undergraduate coauthors, Kade Stewart and Caitlin Phelan, agree.

On their way to a city near you?

In their native Japan, the East Asian Joro spider colonizes most of the country. Japan also has a very similar climate to the US and is approximately the same latitude.

The present study builds on previous work from Davis’ lab that showed Joro spiders are well equipped to spread through most of the Eastern Seaboard due to their high metabolism and heart rate. The spiders are also cold tolerant, surviving brief freezes that kill off many of their orb-weaving cousins.

Their hardiness is one trait that’s enabled the spiders to explode in population stateside, with numbers easily in the millions now. The new research suggests that the Joros’ tolerance of urban vibrations and sounds is likely another factor in the species’ exponential growth.

But their spread shouldn’t be too alarming, the researchers say. The spiders are rather timid.

Source: University of Georgia