Biologist Karen Vanderwolf during her latest visit to a dead beaver carcass sprouting mushooms in the depths of a New Brunswick mine.Donald McAlpine/Supplied
This spring, Karen Vanderwolf took a trip back east to visit an old friend: a dead beaver stashed in an abandoned New Brunswick mine nearly a decade ago.
Donning her caving gear, the biologist clambered through the dark, sometimes in knee-deep water, until she worked her way to dry spot about 500 metres from the mine’s entrance. The beaver was there, decomposing on its bed of rubble and nearly unrecognizable – except for its long, orange-coloured incisors, as sharp as carpenter’s chisels.
Among the cadaver’s protruding teeth and bones were four tiny mushrooms.
“I definitely smiled when I saw that,” said Dr. Vanderwolf, a postdoctoral researcher at the University of Waterloo. “It’s satisfying to know our experiment worked so well.”
Canada’s wildlife, from the caribou to the Douglas fir, is a source of wonder and national pride. But Dr. Vanderwolf has the distinction of adding something uniquely macabre to the country’s compendium of biodiversity: a mushroom that loves corpses.
The biological details on the mushroom growing out of the dead beaver were published earlier this year in the Mycologia research journal. But the official account doesn’t capture the full flavour of a great Canadian science story: One that features curiosity, determination and an unlikely case of mistaken identity.
It began 10 years ago, when Dr. Vanderwolf, a specialist in bat conservation, was working at the New Brunswick Museum in Saint John prior to earning her PhD. Her job included surveying caves across the province to monitor the impact of white nose syndrome: a fungal infection that has devastated bat populations in eastern North America since it was first identified in 2006. New Brunswick scientists have witnessed the fungus sweeping through local bat populations and have documented the consequences.
The biological details on the mushroom growing out of the dead beaver were published earlier this year in the Mycologia research journal.Donald McAlpine/Supplied
The quest to find bats eventually led Dr. Vanderwolf and her colleagues to the old copper mine on the Chignecto Isthmus that connects New Brunswick with Nova Scotia. She had already been down the mine several times in March, 2014, when she and Donald McAlpine, the museum’s head curator of natural science, came across a dead muskrat – not a beaver – sprawled on the floor of a lightless passage leading to the mine’s flooded lower reaches.
How the muskrat came to be there is unknown, but it was enough of an oddity that the researchers were sure to take a second look when they were back in the mine the following December to observe bats in hibernation. This time, however, the muskrat was sporting some mushrooms on the decaying flesh of its tail.
“We knew right away it was special,” Dr. Vanderwolf said.
Special and also very weird. Mushrooms may be a common sight growing in soil or on rotten wood, but a on a dead animal, it’s a very different story. Intrigued and excited, the researchers tried to collect some specimens for further study, but this proved difficult.
“The mushrooms are very delicate, fragile, and lacey,” Dr. Vanderwolf said. “This makes it hard to get them back to the lab for analysis because they fall apart so easily.”
The beaver decomposing on its bed of rubble and nearly unrecognizable – except for its long, orange-coloured incisors, as sharp as carpenter’s chisels.Donald McAlpine/Supplied
Back in Saint John, they consulted with mushroom experts and realized that they had stumbled onto something truly rare. But to learn more, they would need more mushrooms: “So we decided to add more carcasses.”
Conveniently for the scientists, the provincial government had a ready supply, which authorities collect for various reasons, including as seized booty from illegal trapping. When Dr. McAlpine reached out to the province looking for muskrats, however, there were none to be had. Instead, he was offered three beavers from the province’s frozen inventory.
“They were our second choice, but we thought, sure, let’s try the beavers,” Dr. Vanderwolf said.
The frozen beavers were duly sent to the museum in time for their next trip to the mine in July, 2015. In a hurry to get going on the long drive, Dr. Vanderwolf went to the museum’s walk-in freezer, where the beavers were waiting, well-packed inside black garbage bags. She unwrapped one bag, then another. Each contained a beaver. Satisfied, she loaded up all three bags and headed for the mine with Dr. McAlpine.
Getting the specimens down into the mine was the next challenge. For those unaccustomed to handling Canada’s national rodent, a frozen adult beaver weighs in at somewhere north of 50 pounds. In scientific terms, carrying three times that load into a dark, wet mine is known as a slog.
Eventually, the scientists arrived at their destination. It was at this point that Dr. Vanderwolf opened the only bag she hadn’t previously checked to find herself staring at a porpoise.
It’s hard to know what a paleontologist in some future era would make of a porpoise skeleton found in a copper mine. The researchers ultimately decided it would be best to avoid such a scenario. The porpoise was dutifully hauled back out of the mine for the return trip to Saint John.
Meanwhile, the experiment proceeded with the remaining two frozen beavers. One of these was placed beside the muskrat, which by this time was barely a splotch. The second was positioned about three metres away.
The scientists extracted complete mushrooms along with some of the beaver’s flesh to preserve their structure.Karen Vanderwolf/Supplied
When Dr. Vanderwolf and Dr. McAlpine returned the following year, the first beaver carcass was nowhere to be found. The second beaver had mould but no mushrooms. Nothing changed by the next visit in 2017.
Then came a gap in visits, exacerbated by the pandemic. In total, it would be another five years before the researchers could return to the mine in April, 2022. To their amazement, they found the second beaver now covered in mushrooms.
“I don’t know when the mushrooms first appeared, but they finally did,” Dr. Vanderwolf said.
Results from that 2022 visit were revealing. The scientists extracted complete mushrooms along with some of the beaver’s flesh to preserve their structure. A genetic analysis pointed to Coprinopsis laanii, a species previously known to live on tree stumps and cut wood, especially in northern Europe. Until now, none have ever been seen growing on a carcass.
“You don’t know what doors are going to open when you find things like this,” said Scott Redhead, a research scientist with Agriculture and Agri-Food Canada in Ottawa and curator of the National Mycological Herbarium.
Dr. Redhead, who was not involved in the analysis, said that another possible interpretation of the data was that the mushrooms belonged to a new species closely related to the European version. Either way, he added, the discovery merits further study because it raises questions about how the mushrooms derive nutrition from the animals they colonize – or whether they may instead be living off the bacteria involved in breaking down the carcasses.
After visiting the beaver again this year, Dr. Vanderwolf said she sees the entire exercise as a rewarding side project that was simply too interesting not to pursue.
“The scientific impulse to investigate comes from a deep curiosity and a commitment to understanding the natural world, however strange,” she said. “No one will fight to preserve our natural heritage if no one knows about it.”