According to Gram Research analysis, invasive Joro spiders eat at least 26 types of prey that native spiders don’t consume, suggesting they rely on different food sources rather than competing directly with native species. A 2026 study of 52 sites found that native spider diets remained unchanged whether Joro spiders were present, indicating minimal food competition between invasive and native orb-weaving spiders.
Scientists studied what the invasive Joro spider eats compared to native spiders already living in the United States. Using DNA analysis of spider stomachs, researchers found that while Joro spiders and native spiders eat some of the same prey, Joro spiders have their own unique food sources that native spiders don’t eat. This suggests that Joro spiders may not directly compete with native spiders for food, which is good news for protecting native spider populations. However, researchers say more study is needed to fully understand how Joro spiders affect local ecosystems.
Key Statistics
A 2026 research article analyzing DNA from spiders at 52 U.S. sites found that Joro spiders consumed at least 26 unique prey taxa not detected in the diets of three native orb-weaving spider species.
According to the 2026 study published in PLoS ONE, native spider diets were similar regardless of whether Joro spiders were present at collection sites, suggesting the invasive species does not alter native spider feeding patterns.
DNA metabarcoding analysis of female spiders across 52 locations revealed that while Joro and native spiders shared some prey overlap, overall diet composition was dissimilar between invasive and native orb-weaving species.
The Quick Take
- What they studied: Whether invasive Joro spiders eat the same food as native spiders and if they compete for prey
- Who participated: Female spiders collected from 52 different sites across the United States where Joro spiders have spread, including Joro spiders and three types of native orb-weaving spiders
- Key finding: Joro spiders ate at least 26 types of prey that native spiders didn’t eat, suggesting they use different food sources and may not directly compete for meals
- What it means for you: Joro spiders may be less of a threat to native spider populations than initially feared, though scientists need more research to confirm this finding
The Research Details
Researchers collected female spiders from 52 locations across the United States where Joro spiders have established themselves. They examined what was inside the spiders’ stomachs using advanced DNA technology called metabarcoding, which can identify tiny pieces of prey DNA. This method is like reading a receipt that shows exactly what each spider ate. The scientists compared the diets of Joro spiders with three native orb-weaving spider species to see how much their food choices overlapped.
The team also checked whether native spiders ate different things depending on whether Joro spiders were present at their collection site. This helped them understand if the presence of invasive spiders changed what native spiders hunted. By analyzing DNA from hundreds of spider stomachs, the researchers could identify specific prey species and count how common each type of food was in different spider diets.
This research approach is important because it gives scientists a clear picture of what spiders actually eat in nature. Traditional methods of watching spiders or finding prey remains are limited and incomplete. DNA analysis reveals the full diet, including tiny insects that would be impossible to identify otherwise. Understanding food competition is crucial when invasive species arrive, because if they eat the same things as native species, they could starve native populations and cause them to disappear.
The study used modern molecular technology (DNA sequencing) that is reliable and widely accepted in scientific research. The researchers collected samples from 52 different locations, which provides good geographic coverage of where Joro spiders live. However, the study only examined female spiders, so the results may not apply to males. The sample size for individual spider species wasn’t specified, which makes it harder to judge how confident we can be in the results. The study is published in PLoS ONE, a reputable peer-reviewed journal, which means other scientists reviewed the work before publication.
What the Results Show
The main discovery was that Joro spiders and native spiders eat quite different diets overall, despite some overlap in prey types. Joro spiders consumed at least 26 types of prey that were not found in any of the native spider diets. This suggests that Joro spiders have found their own food sources and aren’t directly stealing meals from native spiders.
Interestingly, the native spiders’ diets looked the same whether or not Joro spiders were present at the collection site. This means that the presence of invasive Joro spiders didn’t seem to change what native spiders were eating. If Joro spiders were causing native spiders to go hungry, we would expect to see native spiders eating different prey in areas with Joro spiders, but that didn’t happen.
The research shows that while there is some overlap in prey consumption between Joro and native spiders, the amount of competition for food appears to be limited. Joro spiders seem to have specialized in catching certain types of insects that native spiders don’t typically hunt.
The study found that Joro spiders are generalist predators, meaning they eat many different types of prey rather than specializing in just one or two types. This flexibility in diet may help explain why Joro spiders have spread so successfully across the United States. The research also revealed that different native spider species had somewhat different diets from each other, showing that multiple spider species can coexist by eating different prey.
Previous research on invasive species has shown that introduced predators often compete heavily with native species for food, which can harm native populations. This study suggests that Joro spiders may be different—they appear to have found a niche with unique food sources. However, scientists note that this is just the beginning of understanding Joro spiders’ impact. Other factors beyond diet, such as where spiders build their webs and how they interact directly with each other, could still affect native spider survival.
The study only looked at female spiders, so we don’t know if male Joro spiders eat the same things. The research examined stomach contents at one point in time, so it doesn’t show how diets change with seasons or over years. The study didn’t measure how much prey was available in the environment, so we can’t tell if Joro spiders are eating rare prey that native spiders need. Finally, the sample sizes for individual spider species weren’t reported, making it unclear how many spiders of each type were actually studied.
The Bottom Line
Based on this research, there is moderate confidence that Joro spiders do not directly compete with native spiders for food. However, scientists recommend continued monitoring of native spider populations in areas where Joro spiders have spread. More research is needed before making strong conclusions about whether Joro spiders are safe for native ecosystems.
Ecologists, conservation scientists, and people concerned about invasive species should pay attention to this research. Homeowners in areas with Joro spiders may find this reassuring, though the spiders’ overall impact on ecosystems remains unclear. Agricultural scientists interested in natural pest control should follow future research on this topic.
The effects of invasive species on ecosystems often take years or decades to fully appear. Scientists recommend monitoring native spider populations for at least 5-10 years to see if Joro spider presence causes long-term changes.
Frequently Asked Questions
Do Joro spiders compete with native spiders for food?
A 2026 study of 52 sites found that Joro spiders eat at least 26 prey types that native spiders don’t consume, suggesting limited direct food competition. Native spider diets remained unchanged in areas with Joro spiders present.
What do Joro spiders eat compared to native spiders?
Joro spiders consume many unique prey items not found in native spider diets, though some overlap exists. DNA analysis showed Joro spiders are generalist predators eating diverse insects, while native spiders have more specialized feeding patterns.
Are invasive Joro spiders bad for native spider populations?
This study suggests Joro spiders may not directly harm native spiders through food competition. However, researchers emphasize more research is needed on web placement and spatial overlap to fully understand the invasive spider’s ecosystem impact.
How did scientists figure out what spiders eat?
Researchers used DNA metabarcoding, a molecular technique that identifies prey DNA in spider stomachs. This method reveals exactly what spiders consumed, including tiny insects invisible to the naked eye.
Should I be worried about Joro spiders in my area?
Based on this research, Joro spiders appear unlikely to starve native spiders through food competition. However, their overall ecosystem effects remain unclear, and scientists recommend continued monitoring of native spider populations.
Want to Apply This Research?
- Track native spider sightings in your area by species and location. Record the date, location, and spider type (if identifiable) to contribute to citizen science monitoring of how native spider populations change over time.
- If you live in an area with Joro spiders, document spider sightings and report them to local universities or invasive species programs. Take photos of native spiders you encounter to help scientists track population changes.
- Set up a monthly spider observation routine in your yard or local park. Record the number and types of spiders you see, noting whether Joro spiders are present. Compare your observations across seasons and years to track long-term trends.
This research provides important information about Joro spider diets but does not represent a complete understanding of their ecosystem impact. The study examined only female spiders and stomach contents at one point in time. While this research suggests limited food competition, Joro spiders may affect native species through other mechanisms not studied here, such as direct predation, web placement competition, or habitat changes. Consult with local wildlife experts or invasive species programs for region-specific guidance. This article is for educational purposes and should not replace professional ecological or pest management advice.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.