Counting creatures is critical for conservation, but traditional census-taking is laborious and costly. Over the last decade, biologists have turned to environmental DNA (e DNA)—genetic material shed by living things and collected from scat, soil, water, and air—to monitor endangered species and detect invasive ones.

More recently, scientists have uncovered an e DNA gold mine: spiderwebs. The naturally sticky material traps bio-detritus like saliva and pollen from nearby plants and animals. Every living thing sheds copious DNA, and webs easily ensnare it. "It's probably one of the best substrates we've used and tried to date," says Joshua Newton, a molecular ecologist at Curtin University in Perth, Australia. Newton compared biodiversity in spiderwebs with other sources near a zoo and wildlife sanctuary outside Perth. No passive tool matched spiderwebs' ability to identify vertebrates, echoing results from a similar study conducted in France.

To gather meaningful data, researchers had to destroy about 40 webs. That problem caught the attention of Angela Mc Gaughran, a genomicist at New Zealand's University of Waikato. She wrapped coat hangers with faux webs from a Halloween store and hung them outside. The synthetic material snagged e DNA from nearby cows, sheep, and exotic birds, and detected fungal spores better than real webs. Her group is now developing larger experiments to see whether artificial webs can cheaply mimic spiderwebs' DNA-snagging superpowers.