On a summer day in Somers, Wisconsin, Dave Giordano heard an unexpected buzzing in his back yard. What he found shocked him – a rusty patched bumblebee nest. The discovery was so rare it made the local news.
Once widespread across the midwest and eastern US, the rusty patched bumblebee has seen its population plunge by nearly 90%, prompting its listing in 2017 as the first federally endangered bumblebee in the US.
Each spring, a solitary rusty patched bumblebee queen emerges from hibernation and starts a colony – often in an abandoned rodent burrow. She raises workers through summer, then shifts to producing males and new queens, or ‘gynes’. After mating, the gynes burrow into the soil to overwinter, while the rest of the colony dies off.
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Main image: Two rusty patched bumblebee gynes in the nest discovered by Dave Giordano in August 2023. Below: Jay Watson, a conservation biologist, observes a nest (marked with orange flags) found in a rodent burrow
Since the species was listed, only a dozen nests have been documented – leaving big gaps in understanding, says Jay Watson, a conservation biologist with the Wisconsin Department of Natural Resources. Most bee conservation work has been focused on planting flowers, but nesting habitat is just as important, adds Amy Toth, an entomologist at Iowa State University. “If they don’t find a good location to nest, the entire colony can fail.”
Finding those nests has proved exceptionally difficult, however. Scientists are spending a significant amount of time searching, and not finding any, says Watson. To improve their odds, researchers have turned to conservation detection dogs.
Laura Holder, co-founder of Conservation Dogs Collective, began using labrador retrievers Ernie and Betty White to sniff out bumblebee nests four years ago. Since then, they’ve located 18 nests, though none have belonged to the rusty patched bumblebee. “Bee nests are really hard to find,” says Holder, but “the smell is always there, so the dogs can use their noses to find things we just can’t see.”
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Laura Holder, executive director of Conservation Dogs Collective, and trained detection dog Ernie locate a potential bumblebee nest
Despite years of searching, most nests have been found by chance – often by trained volunteers like Giordano. As part of the Wisconsin Bumble Bee Brigade, a community science programme that trains people to identify and report bumblebee sightings, he recognised the nest’s significance and quickly alerted officials. “They were pretty excited when they got the video and photos,” he recalls.
Time is critical when a nest is found. Researchers often have just a week or two before a colony dies back at summer’s end and is consumed by wax moths, says Watson. After the nest in Giordano’s yard expired, Watson and others carefully excavated it, tracing an extensive network of rodent tunnels. The football-sized nest – filled with spent cocoons, pollen, and dead bees – was sent for analysis.
Scientists estimate the nest produced as many as 1,000 bees, including up to 50 gynes –new queens that, with luck, would go on to establish colonies the following spring. “By all measures, this is what we want to see happen,” says Judy Cardin, an educator with the Wisconsin Bumblebee Brigade who helped excavate the nest.
Giordano’s back yard may not have been a random choice. As executive director of Root-Pike Watershed Initiative Network, a nonprofit focused on restoring local habitats, he had spent years improving his land – removing invasive buckthorn and planting native wildflowers. His discovery underscores the value of back yards in bumblebee conservation.
Recognising this, Cardin encourages homeowners to plant native wildflowers, allow natural habitat for nesting and hibernation sites and avoid applying harmful chemicals. “We might not be able to help the endangered rhinoceros,” she says, “but this is something we can do.”
Toth emphasises the important role volunteers play in tracking rusty patched bumblebees and urges people to log sightings on platforms like the Wisconsin Bumblebee Brigade, Bumblebee Watch, and iNaturalist. “Your observations matter,” she says. “We’re in a cool period of time where you can just sit in your yard and participate in the conservation of endangered species.”
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Jade Kochanski, a PhD student at the University of Wisconsin-Madison nets a bumblebee as it feeds. Lily Landre, a research technician at the university the bee in a sample tube, then collects samples
At the same time, scientists are working to make the most of each nest discovery. Watson and co-authors recently published a framework to help researchers quickly and consistently collect data when a nest is found. “Instead of the crazy mess that has been happening in that two-week window or so, we’re trying to get people to think about it ahead of time,” says Watson.
Toth, who was not involved in the paper, welcomes the effort, calling it a much-needed roadmap for future discoveries that will help researchers better understand the species’ nesting needs as more data is collected.
Whether the species can be saved remains uncertain, but researchers are cautiously optimistic. Insects can rebound quickly, says Watson, though threats like pesticides and extreme weather are difficult to control. Toth adds that the rusty patched bumblebee has become a poster child for pollinator conservation – galvanising awareness and action. “When we get a critical mass all moving toward the same common goal,” she says, “that’s when I feel like there is hope.”
