Published: February 10, 2018

Tsavo Lions

Were bad teeth to blame for these man-eaters’ taste for humans?

Four visitors stand together in front of two Lions of Tsavo dioramas. The leftmost visitor takes a picture of two lion skulls displayed on pedestals near the lions inside the diorama case.

Tucked within an arresting collection of taxidermied mammals of Africa in the Rice Gallery, the man-eating lions of Tsavo are two of the Field Museum’s most famous residents—and also the most infamous.

In March 1898, the British started building a railway bridge over the Tsavo (SAH-vo) River in Kenya. But the project took a deadly turn when, over the next nine months, two maneless male lions mysteriously developed a taste for humans and went on a killing spree.

The rise and fall of the Tsavo lions

Crews tried and failed to scare the lions away, forcing people to flee the area and halting construction on the bridge. Lt. Col. John Henry Patterson, the civil engineer at the helm of the railway project, took matters into his own hands so that work could continue on the railway.

The lions’ reign of terror ended when Colonel Patterson (no relation to our current MacArthur Curator of Mammals Bruce Patterson) shot and killed them in late 1898, and the railroad was completed a few months later.

He later told the story of the lions, and the hunt that eventually took them down, in his book The Man-Eaters of Tsavo and Other East African Adventures. Patterson reported that the lions’ feeding frenzy took the lives of 135 railway workers and native Africans. Later research by Field Museum scientists drastically reduced that estimate to 35 (which is still disconcerting!).

Lt. Col. John Henry Patterson with the first Tsavo man-eater.

The lions have intrigued Field Museum visitors, including this group of students from the 1950s, as long as they’ve been on display.

John Bayallis

The lions’ journey to Chicago

Patterson turned the fearsome felines into trophy rugs from his hunt, and they remained harmless floor ornaments until 1925, when he sold them to the Field Museum during a trip through Chicago.

Museum staff restored the lions to their former glory—minus the appetite—by mounting them as taxidermy specimens and displaying them in a diorama.

In addition to Patterson’s written account, several movies are based on his tale of the man-eating lions, including The Ghost and the Darkness. The 1996 film contained some glaring inaccuracies, including casting lions with manes for the part, but the story captivated moviegoers and increased interest in these infamous lions.

A third man-eating lion from Mfuwe, Zambia, dined on six people in 1991. That specimen is also on display in the museum, on the ground level.

How we study the Tsavo lions

Using archival documents, Assistant Collections Manager Tom Gnoske and Adjunct Curator Julian Kerbis questioned whether the lions had eaten as many people as initially reported. In 2008, a team of scientists including the Field's Bruce Patterson helped discover just how many people they ate. The scientists examined the lions’ skeletons and pelts—specifically, their bone collagen and hair keratin levels—to get a more accurate picture of what the lions had been eating in the months leading up to their death. This research revealed that the lions ate closer to 35 humans—about 100 fewer than Colonel Patterson’s original estimate.

The bigger mystery, though, is why the Tsavo lions got an appetite for people. Was it food scarcity and desperation? A habitual dietary choice made after feasting on the remains of conveniently already-dead railway workers? Or was it the crippling aftereffects of dental injury?

The skull of one of the Tsavo lions shows its teeth, including a large, pointed canine tooth.

Studying the lions’ teeth provides clues, and brings up more questions, about what led the Tsavo lions to kill humans.

Bruce Patterson and JP Brown

Several researchers—including Bruce Patterson and Larisa DeSantis of Vanderbilt University—have been just as captivated by these lions as the museumgoers who flock to the display. Using state-of-the-art technology to research the lions’ skulls, they found that the wear patterns on their teeth resembled those of zoo lions, which eat soft foods and do not crack bones. Previous X-ray imaging of the lions' remains found that they suffered from severe dental issues, including a root-tip abscess in one lion’s canine.

Researchers now believe the lions of Tsavo—as well as the Mfuwe lion also on display at the Field—switched to humans for practical reasons: they were easier to catch and chew.

Research continues today. After rediscovering the cave deemed the "Man-Eaters' Den" in 1997, Gnoske and Kerbis continue to explore the mysteries of the Tsavo lions, including studying hairs from various prey the lions ate.

After finding the cave referenced in Colonel Patterson’s book, a 1998 research project brought together Field Museum and Kenyan scientists. Together, they explored and excavated the area around the cave.

John Weinstein

In November 2017, researchers used X-rays to examine which lion’s skull was matched with which skin during the taxidermy process. Don’t worry: preparators wore protective attire and stepped out of the display case while images were captured.

The importance of museum collections

The lions of Tsavo drive home the fascination and importance of museum collections. Bruce Patterson says:

"It’s astonishing that, [more than a hundred] years after their death, we can be talking about not only how many people they ate, but differences in the behavior of two animals, all from skins and skulls in a museum collection. When you think of the hundreds of thousands of specimens upstairs and all the stories they have to tell, … the value of museum collections is just astronomical."