Could the infamous Joro Spider, aka Trichonephila clavata, be the new poster-child of invasives? Its intriguing behaviors and rapid expansion throughout the Southeast has kept all of us on our toes. This auspicious spider, which is native to Japan, Korea, Taiwan and China, is considered beneficial. It first came to Georgia about 2013 – most likely by catching a ride on a shipping container. Over the past decade, the Joro Spider has proliferated, with millions now inhabiting the Southeast, raising questions about its ecological impact and behaviors.
Researchers described for the first time last week that these spiders commit nonsexual cannibalism when conditions are right. Soon after they were introduced here, researchers found that female Joro Spiders frequently attack each other and cannibalize one another, shattering former expectations about their behavior.
Rapid Expansion in the Southeast
The Joro Spider’s saga to the U.S. started back in 2013, when it was first discovered in Georgia. Ever since, it has continued to rapidly expand throughout the Southeast, with confirmed sightings from Florida to North Carolina. The spider’s remarkable parachuting ability enables it to travel great distances, aiding its rapid spread.
Today, millions of Joro Spiders are spreading across Southeastern states. Their presence has spurred fears of ecologists nationwide of local declines in spider populations. The Joro Spider’s introduction has been associated with a rapid decline in native Georgia spider species.
“Given that they’ll eat each other, it implies that if their densities get really high, they may kill off their own competition,” – Andy Davis
Cannibalistic Behavior Uncovered
New research has shown that female Joro Spiders can brood against each other to aggressive and lethal effect. In these controlled laboratory experiments, fights only happened 40% of the time when two equally-sized females were put together. In contrast, when females of varying sizes were mixed, physical fights occurred just 18% of the time.
What’s perhaps most interesting is that researchers discovered larger female Joro Spiders weren’t necessarily the aggressors in these side-eye-inducing face-offs. This surprising behavior indicates a previously overlooked, more complicated social interaction between these spiders.
“It’s odd because we initially thought joros were pretty shy based on our previous work,” – Andy Davis
In many of these field trials, marauders successfully killed and cocooned their foes in silk before the matches were over. Over all laboratory trials, six of these encounters ended with the death of a single female Joro Spider. This indicates that cannibalism can be expected in populations at high density.
Ecological Implications and Public Perception
The political implications of this cannibalistic behavior are profound. The Joro Spider invasion is spreading fast and wide. This rapid expansion raises concerns over its ability to self-regulate its population size and the harm it can cause to surrounding ecosystems.
Invasive species experts were quick to qualify their praise by saying that the Joro Spider can sometimes be aggressive towards its own species. Fortunately, it isn’t dangerous to people.
“They’re no more dangerous than any backyard garden spider,” – Andy Davis
The rapid spread of Joro Spiders has intrigued, amazed, and alarmed residents and ecologists since they arrived. It’s their beautifully impressive looks and bizarre lifestyles that first draw us in. As they continue to spread, understanding their interactions and ecological role becomes essential for managing their impact on native species.