Tooth decay turned this lion in Kenya that Colonel John Patterson killed in 1898 into a man-eater.

© The Field Museum

Why did these lions eat 35 men? Bad teeth

In 1898, two male African lions killed 35 people in the Tsavo region of Kenya. Their 9-month reign of terror ended when Colonel John Patterson of the British Army shot them dead. Scientists have long debated why the lions began eating people. Now, two researchers have a new answer: They blame tooth decay for the big cats’ taste for human flesh. The finding might also explain why other lions sometimes turn into human eaters.

Lions normally consume a diverse variety of animals, including buffalo, wildebeest, giraffe, zebra, and antelope. Humans figure into their diets only rarely. In the 3 months before their deaths, however, the Tsavo human eaters got nearly 30% of their food from people, according to one recent study. Did the lions focus on humans because they were desperate? Many scientists think so. Apparently suffering from starvation—likely because drought or disease had ravaged their usual prey—they turned to another toothsome delicacy.

But other researchers have turned up conflicting evidence. Larisa DeSantis, a paleontologist at Vanderbilt University in Nashville, wanted a look at the lion’s preserved teeth after reading a frightful passage from Patterson’s 1907 account, The Man-Eaters of Tsavo: “I have a very vivid recollection of one particular night when the brutes seized a man from the railway camp and brought him close to my camp to devour. I could plainly hear them crunching the bones, and the sound … rang in my ears for days afterwards.” If the lions were that hungry, DeSantis reasoned, they must have also scavenged carcasses, a process that involves heavy bone crunching and wears down the teeth in predictable patterns.

The skull of one of the Tsavo man-eating lions

Bruce Patterson and JP Brown © The Field Museum

To find out, she and a colleague analyzed the lions’ jaws and teeth, as well as those of a third human eater from Zambia—all stored at the Field Museum of Natural History in Chicago, Illinois. They used a technique that can determine whether an animal is eating mostly flesh, bones, or some combination of the two. They then compared the patterns on the human eaters’ teeth with those of 53 wild lion specimens from across Africa, two from India, and five captive lions. Next, the scientists examined the patterns on the teeth of cheetahs, which dine solely on flesh, and hyenas, which typically consume entire carcasses—including the bones.

The Tsavo lions’ teeth did not look like those of hyenas, DeSantis says. Instead, the wear patterns were “strikingly similar” to those of the zoo lions, which eat soft foods such as beef and horsemeat. She thinks Patterson was actually hearing the sounds of hyenas that dreadful night.

Other research points out why the lions’ dining preference shifted. One lion—the one that ate the most flesh—was known from a previous study to suffer from dental disease. A painful abscess at the root of one of his canines would have made normal hunting—grabbing and suffocating large prey—impossible, DeSantis says. His partner also had dental and jaw injuries, but these were less serious. The Zambian human eater, which did not consume bone, was also suffering from severe damage to its jaws. Together, this means that dental injuries and disease likely led these lions to softer foods, the researchers write today in Scientific Reports.

“[This] provides first-hand information straight from the lions’ teeth that there is little evidence to support bone eating by the Tsavo lions,” says Jack Tseng, a vertebrate paleontologist at the State University of New York in Buffalo who was not involved in the study. “Any human bone consumption at the time was much more likely the work of the usual suspects—hyenas—than meat-specializing felines.”

But the scientists emphasize that bad teeth alone do not make lions into human eaters. “[They] probably targeted humans because they were easy and had soft flesh,” says DeSantis, noting that the cats didn’t consume entire carcasses. They were also doing what lions do best: hunting opportunistically from a menu that has, since the emergence of early humans, occasionally included people.