A spiderweb’s sticky surface is known for helping arachnids catch their prey. But there’s another function for the glue-like substance covering a web’s delicate strands: it also traps environmental DNA, allowing scientists to understand more about the animals living in the spiderweb’s vicinity.
Loyola Marymount University Professor Demian Willette, Ph.D., who created an eDNA device to help identify and track fish species, this fall has partnered with the San Diego Natural History Museum to collect biological samples from spiderwebs. These webs contain clues about the biodiversity that exists in San Diego County’s urban canyons – home to gray foxes, garden slender salamanders, birds of prey and more.
“Spiderwebs are gathering an immense amount of biological information,” said Willette, associate professor of biology in LMU Frank R. Seaver College of Science and Engineering.
Willette leads the Willette Lab of Applied Ecology, which focuses on conservation in both marine and terrestrial environments, including restoring native biodiversity, managing invasive species, and combating illegal, unreported, and unregulated (IUU) fishing and seafood fraud.
While the lab’s work collecting environmental DNA from marine fisheries is well documented (Willette and collaborators also hold a U.S. patent for an eDNA sample-collection device), the team’s use of spider webs to detect biodiversity is fairly new. Scientists have begun to look to the webs as a way to passively gather data and complement traditional on-the-ground survey methods. Preliminary data shows a sample of just four spiderwebs can yield traces of DNA from dozens of species.
Willette’s first initiative involved using spiderweb environmental DNA to detect biodiversity in Ascot Hills Park, home to an urban micro-forest just east of downtown L.A. In this study, biology student Sabriya Seid (B.A. 2025) and lab members detected more than 200 species from web samples, roughly three times the number of species observed in visual surveys.
“An obstacle to monitoring urban wildlife is that animals are really good at hiding when people are around,” Willette said. “This tool helps us detect who’s nearby, even if we can’t see them, including nocturnal coyotes, cryptic insects, and even invasive species.”
In San Diego County, the Willette Lab worked with local residents to collect 48 samples of spider webs that were handed to the team for analysis in the lab. So far, they’ve detected at least 50 unique species, including gray fox, garden slender salamander, and birds, such as the lesser nighthawk (all of which are difficult to find using traditional surveys).
“Spiderwebs behave like a piece of tape hanging midair,” shared Rachel Larson, Ph.D., postdoctoral researcher at the San Diego Natural History Museum. “DNA particles that are floating in the wind can be carried and trapped in the web — we’re sampling what’s lodged in there.”
Like much emerging research, there are still many questions the scientists are asking, such as how far eDNA can travel in the wind, or what kinds of spiders create the best webs to capture eDNA particles.
