Rodent DNA reveals black market trade in furs

Rodent DNA reveals black market trade in furs

Rodent DNA reveals black market trade in furs

This article is from Hakai Magazine, an online publication about science and society in coastal ecosystems. Read more stories like this at

The two land masses that make up most of New Zealand – the North Island and the South Island – are less than 25 kilometers apart but couldn’t be more different. Home to the country’s largest city, Auckland, the North Island is known for towering volcanoes, legendary surfing beaches and a relatively mild climate. On the colder and quieter South Island, the rugged landscape is dotted with crystal-clear lakes, rolling glaciers and snow-capped mountains – familiar scenes for fans of the Lord of the rings film trilogy. Recent research shows that the islands’ differences extend all the way down 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 unraveled the origins of New Zealand’s invasive mice through genetic analysis. As expected, the researchers found that house mice in the North Island descended from European mice that hitchhiked on the ships of British colonists two centuries ago.

But when King and her team analyzed mice from the South Island, they discovered that the animals were related to a Southeast Asian mouse, a subspecies widespread in China but never found outside of Asia. The stray mice confused King, who is a resident at the University of Waikato in New Zealand. “We couldn’t imagine where they came from,” she says.

The rodent conundrum deepened in 2019 when researchers at New Zealand’s University of Auckland uncovered the same trend in Norwegian rats. The South Island animals corresponded to a phylum known only from China, while the North Island rats came closest to those of England.

The mounting evidence suggested that rats and mice had traveled to the South Island from China 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 that would explain how the rodents had arrived. King began to suspect that the circumstances of the rodents’ journey were not entirely right.

In 2022, King co-authored a study that offered a tantalizing explanation: The rodents arrived with traders sailing to China to illegally sell New Zealand fur seal pelts, and then returned to the South Island. In the 1800s, the South Island’s rugged coastline was dotted with numerous fur seal colonies, with pelts being the island’s only lucrative commodity. And in Canton (now Guangzhou), a bustling southern China port city that formed the backbone of international trade, seal pelts rose in value as the world’s sea otters and their precious fur became scarce. Those brave enough to circumvent the rules by hunting fur seals could make a fortune.

By the turn of the 19th century, conditions were ripe for shady deals to flourish. The profit-hungry British East India Company tightly controlled its own monopoly on maritime trade, forbidding the colony from direct trade with China and India. Most official merchant ships from London, England made pit stops in Sydney, Australia en route to supply New Zealand’s main port on the North Island.

King suspected that unscrupulous fur traders were bypassing Sydney on their way to and from Canton to evade authorities. “Those who wanted to circumvent the regulations did so very quietly,” she says. Such secret journeys would have eluded the official record.

To determine whether the South Island’s invasive rodents arrived directly from China on official voyages or via a secret shipping route, King and her co-authors compared the rodent DNA to genetic material from 19th-century rat and mouse samples collected near the Sydney Harbor have been excavated.

The results strengthened King’s suspicions. The Sydney house mice had European ancestry, and the rats’ genes matched those of Norwegian rats found in Britain and the North Island. There was no trace of genes from Southeast Asian house mice or the Chinese strain of rats – evidence that the 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 shady dealings through the port. In 1806, colonial authorities arrested Simeon Lord, a Sydney-based ex-convict and seal entrepreneur, for shipping 87,000 seal skins collected in the Antipodean Islands south of New Zealand to Canton via Sydney. But, by some miracle, Lord’s voyage must not have released any rodents.

The renegade traders who evade detection by avoiding official shipping lanes would never have guessed that the genes of stowaway mice and rats could reveal their movements centuries later. “The [rodents] gave them away,” says King.

My Smith says King’s conclusion is plausible, given that many Sydney traders were at least as sneaky and profit-hungry as Lord. “There were all kinds of underhanded deals,” she says.

Although historians had a hunch that a clandestine trade in fur seal pelts took place between Australia and China, the lack of historical evidence has made it difficult to confirm.

Genetic evidence can reveal information about the past that cannot be found in historical records or reports, 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 in Hakai Magazine and is republished here with permission.

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