Tsavo lions, as they've come to be known, live near the Tsavo River in Kenya, and during the late 19th century they were the most feared creatures on the African continent.

During the construction of a railway bridge over the Tsavo River in Kenya, starting in 1898, the unusual behavior of lions began to scare the workers and residents of that region. They hunted and ate human beings incessantly. The railway workers were the main victims.

To try to minimize the attacks, the workers built fences with local trees and lit big fires around their dormitories. To nothing. The two lions responsible for the fear of those people showed uncommon intelligence. They evaded the fences and didn't show fear of fire.

Many victims were surprised in their sleep, pulled out and eaten nearby. The workers disappeared in mysterious ways, perhaps fleeing the threat of working there, perhaps eaten by Tsavo's two male lions.

At first they were not always successful in their efforts to take their victim, but they went on to face any danger to obtain their favorite food. Their methods then became so mysterious, and their lurking and attack so well timed and so certain of success, that the workers firmly believed that they were not real animals, but demons in the shape oflion. - John Henry Patterson, in The Man-Eaters of Tsavo.

Tsavo lions differ in physiognomy with their relatives from the rest of Africa. Males from other localities have large manes, dark or light, and Tsavo lions have short, thin manes or none at all. You could easily mistake it for a female. The bodies of the two males on display at the Field Museum in Chicago.

Popular legend proclaimed until recently that more than 130 people had been killed by the two animals in that period alone, but recent research has shown chemical evidence that, months before they were killed, one of the lions had eaten 10 humans and the other 24. Still frightening numbers.

But why do Tsavo lions like human flesh anyway?

Samuel Kasiki, Deputy Director of Biodiversity Research and Monitoring with the Kenya Wildlife Service, gives a plausible answer to this phenomenon.

"For centuries, Arab slave caravans passed through Tsavo on their way to Mombasa. The mortality rate was high; it was a bad area for tsetse fly sleeping sickness; and the bodies of slaves who died or were dying were left where they fell. So the lions may have acquired their taste for human flesh by eating the corpses," he said.

Even today, even after 100 years of the great lion hunt by humans who worked on the railroad, deaths are common by Tsavo lions.

"When I arrived in Nairobi, news reached the capital that a lion had just killed a woman in Tsavo. A cattle herder had been devoured weeks earlier," Paul Raffaele said in an article for the Smithsonian in 2010, when he set out on an expedition with Bruce Patterson, a zoologist at the Field Museum of Natural History in the United States who has spent the past decade studying lions in the river regionTsavo.

Hunting the lions

To address the incessant killings during the construction of the railroad bridge in the 19th century, the man in charge of the project, Lieutenant Colonel John Henry Patterson, went on a deadly hunt after the two lions.In the book The Man-Eaters of Tsavo he tells his experience with the construction of the railroad and with the lions. The second, lion killed by Patterson, now identified as FMNH 23969. (Image: Field Museum)

After spending several months trying to hunt the animals, waiting in hide at locations the lions had previously attacked, he succeeded in killing one of the males on December 9, 1898, and the second lion 20 days later, from which Patterson narrowly escaped being killed.

Petterson sold their bodies for $5,000 at the time to the Field Museum of Natural History, where, stuffed, they are on display to this day.

Recent researches proved that lions had infected teeth, making it difficult to hunt larger animals and with a harder carcass. Humans, for being fragile and slow animals, were the choice for the two lions of Tsavo not to starve. And even today we are their favorite game, since there are often reports of attacks in the region.

A version of this article appeared in print on December 2019.