Colonial Hanoi Paid a One-Cent Bounty for Every Rat Tail Handed In During the Plague Scare of 1902. Officials Soon Noticed Live Rats Without Tails Going About Their Business in the Streets.

At the turn of the twentieth century, Governor-General Paul Doumer set out to make Hanoi the showpiece of French Indochina. The European quarter got wide, tree-lined avenues, large villas and, beneath them, what the colonial administration proudly recorded as more than fifteen kilometres of sewer pipe. Those homes had running water and flush toilets. The Vietnamese neighbourhood of the Thirty-Six Streets, which bore most of the tax burden, got a drainage system that emptied into the nearby lake or the Red River and backed up every rainy season.

Rats had always lived in the native quarter, and the French had never minded much. Then, in 1894, Alexandre Yersin established the role of rats and fleas in spreading bubonic plague, and plague was moving south from China. The rats, meanwhile, had found the new sewers. According to the historian Michael G. Vann, whose 2003 article in French Colonial History is the principal account of what followed, they were dark, sheltered from predators and connected directly to the city's best addresses. Residents of the French quarter began finding rats coming up through the toilets. When plague cases began to appear, they appeared in the European quarter too.

The Count

In the spring of 1902 the city sent teams of rat catchers into the sewers. They were Vietnamese, because no French colonial was going to do the job, and they were paid by the rat. The archive file Vann found years later in Aix-en-Provence, "Destruction des animaux, Hanoi-Ville", recorded the results. In the first week, 26 April to 1 May, the catchers turned in 7,985 rats. On 30 May they killed 15,041. Daily totals through mid-June consistently topped 10,000, and on 12 June the file records 20,114.

The killing created its own complaints. On 9 June the resident-superior of Tonkin told the governor-general's office that white residents objected to the presence, sight and odour of the rat catchers in their streets. On 16 June Dr Serez, head of health services, replied that the catchers were no dirtier than ordinary sewer workers and that he had received no complaints about them. The catchers, for their part, were not content with their pay. After slow-downs and work stoppages in June and July, the commission was raised from one cent per rat to two, and by 1904 it had reached four.

The Tails

The sewers kept producing rats faster than the catchers could remove them, so the administration opened the hunt to the public. Anyone could collect a one-cent bounty per rat. To spare the municipal health service from receiving thousands of carcasses, possibly carrying infected fleas, only the tail was required. "I always think about that," Vann told Atlas Obscura. "Who is the poor guy counting all these rat tails?"

The tails arrived in thousands. In Vann's account, desk-bound administrators were delighted with the figures, while officials in the field began noticing rats without tails going about their business in the city streets. The explanation did not take long: people were catching rats, cutting off the tails and letting them go, where they could breed and produce more tails. In a later essay on the book, Vann dates the first reported sighting of a tailless rat to July.

The Farms

Then came the story that made the episode famous. According to the 2003 article, health inspectors discovered that "more enterprising but equally deceptive individuals were actually raising rats to collect the bounty" in the suburbs of Hanoi. Faced with this, the colonial regime scrapped the bounty.

The evidence for the farming is less direct than the rat counts. Vann's footnote for it cites not a 1902 inspection report but the Hanoi municipality's annual report for 1930 to 1931, written nearly thirty years later, which also cited rat farming as one of the reasons the earlier campaign had failed. The story has grown in the retelling since. In the 2003 article, inspectors found people raising rats. In a 2012 Freakonomics Radio episode, one health official "discovered a rat farm." By a 2018 interview, it was "rat farms established by locals in suburban villages" and "a black market in trafficking rats all around Tonkin", and his essay on the book described "a region-wide smuggling network bringing rats to Hanoi." The episode is now a standard example of the cobra effect, the incentive that produces more of what it pays to remove. Vann has proposed renaming it. "I'm pushing for the rat effect," he told Freakonomics, "in lieu of the cobra effect."

The Exposition

The bounty did not stop the plague. In 1902 and 1903 Hanoi hosted Doumer's International Colonial Exposition, meant to present the city as a hygienic triumph of French science to visitors and cargo from around the world. Among the cargo, Vann writes, were apparently rats carrying infected fleas, perhaps from British India. They escaped into the new sewers of the European quarter, and when plague struck Hanoi in 1903 it spread through the city and Tonkin over the following months. There were 159 reported cases and 110 official deaths, the great majority Vietnamese, and Vann notes the real figure was certainly higher because families hid deaths from the colonial authorities. Six Europeans fell ill. Two died.

A "violent" outbreak in 1906 emptied part of the city, and the 1906 to 1908 epidemic produced some 263 official plague deaths. By the early 1930s the municipality was noting the continuing threat of rat infestation and saying that nothing could be done about it. Doumer, meanwhile, returned to France and went on to become its president.

The administration had built the sewers to show what French engineering could do for Hanoi, and the rats moved into them. It then paid the population to remove the rats, and the population kept them alive, because a living rat could produce more tails. In 1997, when Vann went to work in the National Library of Vietnam, researchers using the French-era card catalogue had learned to be careful opening the top drawers. Several of them had been used as nests.

Filed from public reporting:

• Michael G. Vann, French Colonial History — "Of Rats, Rice, and Race: The Great Hanoi Rat Massacre, an Episode in French Colonial History"
• Michael G. Vann, H-France Fiction and Film for Scholars of France — "Confessions of a Rogue Historian: Why I Wrote a Graphic History of Colonial Hanoi"
• World History Connected — "Interview with Michael G. Vann"
• Freakonomics Radio — "The Cobra Effect"
• Atlas Obscura — "The Great Hanoi Rat Massacre of 1902 Did Not Go as Planned"
• International Institute for Asian Studies, The Review — "Rats and Sewers in 'Modern' and 'Civilized' French Hanoi"
• Saigoneer — "How Hanoi's Infectious Rats and Impish Locals Bamboozled the French in 1902"