Rodent DNA Reveals Black Market Fur Trade
This article is from the same magazine, an online publication on science and society in coastal ecosystems. Read more stories like this at hakaimagazine.com.
The two landmasses that make up most of New Zealand, the North Island and the South Island, are less than 25 kilometers apart, but they couldn’t be more different. Home to the country’s largest city, Auckland, the North Island is known for its towering volcanoes, legendary surfing beaches, and relatively mild climate. In the colder and calmer South Island, the rugged landscape is crisscrossed with crystal-clear lakes, rolling glaciers and snow-capped mountains – familiar settings for fans of the Lord of the Rings movie trilogy. Recent research reveals that the islands’ differences extend to their rodents. And the findings could change our understanding of history.
It all started two decades ago, when zoologist Carolyn King and one of her students were untangling the origins of New Zealand’s invasive mice through genetic analysis. Unsurprisingly, the researchers found that house mice on the North Island were descended from European mice that hitchhiked on British settler ships two centuries ago.
But when King and his team analyzed South Island mice, they found that the animals were related to a Southeast Asian mouse, a subspecies that is widespread in China but has never been found outside of Asia. The stray mice puzzled King, who works at the University of Waikato in New Zealand. “We didn’t know where they came from,” she says.
The rodent enigma deepened in 2019, when researchers at the University of Auckland in New Zealand discovered the same trend in Norway rats. The South Island animals matched a strain known only from China, while the North Island rats were closest to those from England.
Mounting evidence suggested that rats and mice had traveled from China to the South Island in the 19th century, when New Zealand was still part of the British colony of Australia. But there were no historical records, at least in English, of direct contact between China and the South Island to explain how the rodents had arrived. King began to suspect that the circumstances of the rodents’ journey were not entirely justified.
In 2022, King co-authored a study offering a tantalizing explanation: The rodents arrived with traders who sailed to China to illegally sell the skins of New Zealand fur seals, then returned to the South Island. In the 1800s, abundant colonies of fur seals dotted the rugged South Island coastline, and furs were the island’s only lucrative commodity. And in Canton (now Guangzhou), a bustling southern Chinese port city that provided the backbone of international trade, fur seal skins rose in value as the world’s sea otters and their prized fur became scarcer. Those bold enough to circumvent the rules by hunting sea lions could make a fortune.
By the early 19th century, the conditions were ripe for shady deals to flourish. The profit-hungry British East India Company tightly controlled its own monopoly on maritime trade by forbidding the colony from direct business with China and India. Most of the official trading ships from London, England called at Sydney, Australia en route to supply New Zealand’s main port on the North Island.
King hypothesized that unscrupulous fur traders bypassed Sydney on their way to and from Canton to avoid the authorities. “Those who wanted to circumvent the regulations did so quietly,” she says. Such secret trips would also have evaded official record keeping.
To determine whether the invasive South Island rodents arrived on official voyages or via a secret shipping route directly from China, King and his co-authors compared rodent DNA with genetic material from 19th-century rat and mouse specimens unearthed near the South Island. sydney harbour.
The results reinforced King’s suspicions. The Sydney house mice had European ancestry, and the rats’ genes matched those of Norway rats found in Britain and the North Island. There was no trace of the genes of Southeast Asian house mice or the Chinese strain of rat, evidence that ships carrying rodents from China did not pass through Sydney. Or, most of them didn’t.
Philippa Mein Smith, a historian at the University of Canterbury in New Zealand who was not involved in the research, says there is some evidence of nefarious dealings through the port. In 1806, colonial authorities arrested Simeon Lord, a Sydney-based ex-convict and seal businessman, for shipping 87,000 seal pelts collected in the Antipodes Islands, south of New Zealand, to Canton via Sydney. But by some small miracle, the Lord’s journey must not have let loose any rodents.
Rogue traders who evaded detection by avoiding official shipping routes would never have suspected that the genes of stowaway mice and rats could reveal their movements centuries later. “He [rodents] he gave them away,” says King.
Mein Smith says that King’s conclusion is plausible, given that many Sydney merchants were at least as devious and profit-hungry as Lord. “There were all kinds of undercover deals,” she says.
Although historians suspected that there was a clandestine trade in fur seals between Australia and China, the paucity of historical evidence made it difficult to confirm.
Genetic evidence can uncover information about the past that cannot be found in historical records or accounts, says study co-author Andrew Veale, a vertebrate pest ecologist and geneticist at Manaaki Whenua Landcare Research. “DNA has this ability to tell the story of what really happened.”
This article first appeared on the same magazine and is republished here with permission.