Joro Spiders, Spreading in the Southeast, Can Survive Surprisingly Well in Cities

One of America’s newest arachnids—the black and yellow Joro spider, a species endemic to Eastern Asia—has been expanding its range across the Southeast since it was first confirmed stateside in 2014. And, according to a new study, the large, vibrant spiders are acclimating astonishingly well to cities.

“They’re everywhere,” Alexa Schultz, an undergraduate student researcher at the University of Georgia and co-author of the new study, tells AL.com’s Dennis Pillion. “We noticed along the roadsides, they build almost apartment-style webs, where there’s like a big cluster of them. You’ll see them, for example, like along a power line, and you just look up and there’s a sky full of spiders.”

Unlike most spiders native to the region, Joros appear unfettered by noise, wind and the vibrations of urban ecosystems. They grow to be nearly three inches across and spin unique golden webs that can reach up to ten feet wide. The spiders’ large size, striking color and increasing presence at gas stations, stoplights and other heavily trafficked areas has made the orb-weaving species a spectacle in parts of states such as Georgia, South Carolina, North Carolina and Tennessee.

The Joros’ unstressed behavior was the focus of the new study, which measured the species’ “urban tolerance” and was published earlier this month in the journal Arthropoda.

“If you ever look at a spiderweb next to a road, they’re jiggling and shaking, and it’s a cacophony of stimuli. … Roadsides are a really harsh place for an animal to live. But Joros seem to be able to live next to them,” Andy Davis, an ecologist at the University of Georgia and the study’s lead author, tells CNN’s Taylor Nicioli.

The team traveled to 20 different roads—some busier than others—in northeastern Georgia to study how Joros’ physiology and behavior differed across areas with varying levels of human disturbance. After locating spiders at each site, they touched a tuning fork to their webs, simulating the vibrations of prey being caught, and watched if the Joros moved to attack.

They noticed some variability across a total of 357 trials. Along certain roads, the spiders attacked as often as 80 percent of the time, while at other locations, less than 30 percent did. A “small but significant” correlation was identified between traffic flow and predatory behavior, with busier roads linked to slightly less predation by the Joros, the team wrote in their study. Spiders near moderate- to heavy-traffic roads attacked an average of 51 percent of the time, while spiders near low-traffic roads attacked an average of 65 percent of the time.

Though these findings might make it appear as though the spiders in more urban areas suffered a bit, the team found that crucially, Joros in all locations weighed about the same, indicating an equal level of fitness for the varied habitats. To compensate for traffic disruptions, spiders in busier areas might simply be choosing larger prey, the team hypothesizes. All told, the results support many scientists’ predictions that Joros are primed to spread even more throughout the region and survive throughout the entire East Coast, according to a University of Georgia statement.

Still, scientists are careful not to spin any sensationalist webs about Joros and their potential to spread. Despite the spiders’ proximity and visibility, they are a timid species that poses no threat to humans, even as they move into urban areas.

“They’re not particularly interested in us,” Floyd Shockley, collections manager for the Department of Entomology at the Smithsonian’s National Museum of Natural History, tells CNN. “They’re interested in the fact that we make the condition super easy for them to get the prey that they need to complete their life cycle.”

The new study is one of only a few to focus on Joros in the United States. Much about the spiders, including their impact on native species and ecosystems, remains unknown. But one thing that’s more certain, researchers conclude, is that they’re likely here to stay.

“They’re a media sensation,” David Coyle, a forest health and invasive species researcher at Clemson University, told Wired’s Katrina Miller in 2022. “Lots of things that garner clicks are wrapped up into this one creature. … Our knowledge of them is poor. We know what they are, where they are and we know that populations are increasing exponentially. But we have no clue about the impacts.”

Christian Thorsberg | READ MORE

Christian Thorsberg is an environmental writer and photographer from Chicago. His work, which often centers on freshwater issues, climate change and subsistence, has appeared in Circle of Blue, Sierra magazine, Discover magazine and Alaska Sporting Journal.