A dental disease caused two felines, unable to hunt their natural prey, to devour dozens of railroad workers in Kenya in the 19th century.

Tsavo with one of the man-eating lions he shot.

Contrary to what the cinema tries to show us again and again, humans are not usually the preferred prey of any great beast of land or sea, be they lions, sharks or tigers. But from time to time there are some animals that seem to be unaware of this general rule. What drives certain predators to become man-eaters? If we allow ourselves to be deceived by the seduction of the legend, it is the thirst for our blood, or even an incarnation of evil that takes shape in certain beasts. The reality is more prosaic: a new study published in the journal Scientific Reports concludes that two famous 19th century African lions adopted a cannibalistic diet due to dental disease that prevented them from hunting their usual prey, much more elusive than a sleeping human.

At the end of the 19th century, the British Empire was rubbing its hands at the idea of ​​squeezing the riches of Uganda, known as the pearl of Africa. To open those fertile lands to colonization and exploitation, the London government planned a railway that would link Lake Victoria with the city of Mombasa, on the coast of present-day Kenya. That idea was for some a gigantic madness: more than 1,000 kilometers of railroad overcoming tricky geographical obstacles and crossing territories plagued by beasts, tropical diseases and hostile tribes.

In 1898 the work of the Ugandan railway suffered its greatest setback, when the construction of a bridge over the Tsavo River was delayed for nine months due to the harassment of two lions that at night raided the tents to drag the sleeping workers and devour them. The episode of the man-eating lions of Tsavo would be narrated for posterity by the supervisor of the work, British Army Colonel John Henry Patterson, in his book The Man-Eaters of Tsavo (1907). The cinema has recreated the story on several occasions, the last of them in 1996 with The demons of the night, with Val Kilmer as Patterson and Michael Douglas as a fictional professional hunter.

The lions of Tsavo, exhibited in the museum.

The lions of Tsavo, exhibited in the museum.
The Field Museum

The two Tsavo lions were eventually killed by Patterson. For a quarter of a century, the remains of the animals served as rugs in the colonel’s home, until in 1924 they were sold to the Field Museum in Chicago, which naturalized them and today keeps them on display. As for the total number of victims claimed by the felines, it has never been possible to determine precisely: in his book, the colonel counted “28 railroad workers and lots of unfortunate Africans, of whom no precise record was kept,” according to recalls for EL ESPAÑOL the co-author of the new study Bruce Patterson, curator of mammals at the Field Museum (and no relation to the colonel). However, years later, in a 1925 pamphlet, the author himself inflated his figures: “135 railroad workers and unfortunate Africans,” notes Bruce Patterson. “Exaggerating does not hurt the sale of books: it is still being republished a hundred years later!”, He adds.

Corpses that tell stories

Preserving the skins and skulls of the two lions offers scientists a rare opportunity to apply current advanced techniques to try to piece together the details of that episode. Using an isotope analysis of the remains, a 2009 study estimated the total number of humans consumed by lions at around 35. Researchers can also investigate the reasons that led those animals to specialize in such a peculiar diet.

For years it has been speculated that some large predators will attack humans in periods of scarcity of their natural prey. Tsavo, today a huge national park in Kenya, is a harsh and arid territory covered by dense hawthorn forests, and at the time of the railway’s construction it suffered from a prolonged drought and a viral epidemic that affected wildlife. In his book, Patterson recalled hearing lions chew on a victim’s bones in the distance, suggesting that food shortages forced the animals to take every last calorie from their prey.

However, it seems that the colonel probably added some fantasy to spice up his narrative. Bruce Patterson and evolutionary ecologist Larisa DeSantis, from Vanderbilt University (USA) and director of the new study, have analyzed the teeth of lions, observing that there is no wear expected in a denture dedicated to crushing bones. The two Tsavo lions, DeSantis and Patterson conclude, ate only tender parts, which disproves the prey shortage hypothesis.

Humans, an easy prey

But the researchers did find a peculiarity in the teeth: especially one of the lions had serious injuries in its teeth, probably caused by the kick of a prey, according to DeSantis. “Lions subdue their prey with their jaws, and with injuries like this, hunting would have been less effective,” explains the researcher to EL ESPAÑOL. “These damages would have made hunting a risky and probably painful undertaking, while humans would have been a simple solution to their needs, since they are much easier to subdue than a zebra.”

Other scientists had already proposed that severe jaw injuries could lead big cats to swap their natural prey for human prey; This idea is known as the disease hypothesis. “The injuries to the teeth of the first Tsavo lion are extreme and different from the typical damage that lions usually present; the data from our study are consistent with the theory of the disease ”, concludes DeSantis.

However, DeSantis and Patterson caution that lion attacks on humans do not always hide dental or facial disease. Patterson recalls the case of a certain number of Tsavo lions that escaped the limits of the national park a few years ago, where the population was too large. Some of these animals found wildlife for their supply, but others turned to the only prey available on the adjacent ranches: people and livestock. “With nothing else to eat, lions are dangerous and harmful,” says Patterson. “And his teeth were in perfect shape,” he adds.

The colonel’s namesake recalls the words written by the famous Scottish hunter John A. Hunter, who was a friend and colleague of Denys Finch Hatton, the character played by Robert Redford in Memories of Africa. Hunter believed that man-eating lions used to be old, wounded, or sick animals; But if a healthy lion happened to taste human prey, it would certainly repeat itself. And that this would occur more frequently where livestock had displaced wildlife. DeSantis cautions: This is a rare phenomenon, but it does happen. “In Tanzania, lions killed 563 people between January 1990 and September 2004; in 2016, three lions were implicated in the death of several people in the Gir forest, in India ”. And it will continue to happen, warns the ecologist: “if we reduce the populations of their prey and increase our own, the big cats that eat men can become a more common phenomenon.”