Tsavo Lions’ Teeth Reveal New Secrets About the Man-Eaters

Given the opportunity, lions may well chew on the occasional Homo sapiens who wanders unprotected into their territory. Thankfully, only a small number of Africa’s big cats have developed a habit of deliberately pursuing people as food.

There have, however, been exceptions. Among the most infamous was the case in Kenya’s Tsavo region in 1898, when two male lions terrorised labourers for months as they constructed a railway bridge over the Tsavo River.

The more-than-century-old teeth of these lions - long portrayed as ‘man-eaters’ - are now providing fresh evidence, revealing not only whether they consumed humans but also possible reasons why.

Researchers from the US and Kenya used recent methods for sequencing and studying old, degraded DNA to examine animal hairs lodged in the lions’ teeth.

Their new study identifies specific animals eaten by the lions.

Evidence of this kind could help to verify accounts of the episode, while also offering a better understanding of what might lead wild predators to behave in such an unusual way.

The Tsavo lions’ attacks in 1898

Reports of lion attacks first emerged in March 1898, soon after Lt Col John Henry Patterson, a British Army officer and engineer, arrived to supervise a project intended to link the interiors of Kenya and Uganda by railway.

According to Patterson, the British recruited thousands of labourers, largely from India, to build the bridge and housed them in camps extending over several kilometres.

At first, Patterson questioned reports that lions had carried off two workers. Several weeks later, though, he was persuaded when Ungan Singh, an Indian military officer travelling with him, met the same fate.

Patterson passed that night in a tree, vowing to shoot the lion should it come back. He heard “ominous roaring,” he wrote, followed by an extended silence and then “a great uproar and frenzied cries coming from another camp about half a mile away.”

The following morning, he discovered that a lion had attacked a different section of the camp.

This marked the start of a prolonged effort by Patterson and others to kill the offenders: two large male lions without manes. Maneless males are more frequent in certain places, Tsavo among them, perhaps because of the region’s climate or vegetation.

The attacks suddenly ceased for several months, Patterson recorded, although “from time to time we heard of their depredations in other quarters.”

When the lions eventually reappeared, they appeared more daring still. Rather than striking separately, as they had previously, they often entered camps together.

Patterson ultimately killed both lions in December that year.

The final number of deaths attributed to the lions is uncertain. Some estimates have put it as high as 135, although a 2001 study concluded that the total was more likely to have been about 30 - a much lower number, but certainly not an insignificant one.

Patterson retained the lions’ remains and eventually sold them to Chicago’s Field Museum of Natural History in 1925.

DNA from Tsavo lions’ teeth reveals their prey

Decades afterwards, ecologist Thomas Gnoske, the museum’s collections manager, came across the lions’ skulls in storage and spotted hair fragments trapped in exposed cavities in their teeth.

Some scientists have suggested that damaged teeth drove the lions to hunt humans, as the injuries may have made it difficult for them to overpower larger prey.

Whatever the explanation, the damage appears to have preserved evidence of the lions’ diet. Gnoske and fellow researchers have now completed a detailed investigation of the hairs, using both microscopic and genomic methods.

The first task was to establish the age of the hairs, says co-author Alida de Flamingh, a conservation biologist at the University of Illinois Urbana-Champaign.

“We look to see whether the DNA has these patterns that are typically found in ancient DNA,” de Flamingh says.

After confirming the samples, the researchers focused on mitochondrial DNA, or mtDNA. It is more abundant in cells than nuclear DNA, while hair can retain mtDNA and reduce contamination - useful qualities when dealing with old specimens.

“​​And because the mitochondrial genome is much smaller than the nuclear genome, it’s easier to reconstruct in potential prey species,” de Flamingh adds.

Although the hairs were poorly preserved, they nevertheless produced usable mtDNA. A proportion of the hairs belonged to the lions themselves.

Most of the remainder came from a predictable assortment of local ungulates - apart from one notable finding. The teeth of the notorious man-eaters did indeed contain human hair.

“Analysis of hair DNA identified giraffe, human, oryx, waterbuck, wildebeest and zebra as prey, and also identified hairs that originated from lions,” de Flamingh, Gnoske, and team write.

The lions’ mtDNA indicates that they were brothers, as had been suspected. The analysis also found that they had eaten at least two giraffes and a local zebra.

The researchers additionally compiled a database of mtDNA profiles from potential prey species living in the lions’ habitat in 1898.

They note that the presence of wildebeest mtDNA was unusual, as the nearest wildebeest population at the time was about 80 km away. Yet during the extended pause in attacks reported by Patterson, the lions may have been away hunting wildebeest.

The authors also highlight the discovery of only one buffalo hair and no buffalo mtDNA. “We know from what lions in Tsavo eat today that buffalo is the preferred prey,” de Flamingh says.

That absence may offer a clue to why the lions targeted people.

“Patterson kept a handwritten field journal during his time at Tsavo,” says palaeoanthropologist Julian Kerbis Peterhans of Roosevelt University and the Field Museum. “But he never recorded seeing buffalo or indigenous cattle in his journal.”

Rinderpest, a viral disease affecting ungulates, had arrived in Africa from India several years earlier. It devastated buffalo and cattle populations throughout the region during the 1890s, potentially compelling some lions to seek alternative prey.

For the study, the team chose not to carry out additional tests on the human hairs in an attempt to identify possible victims.

“There may be descendants still in the region today, and to practice responsible and ethical science, we are using community-based methods to extend the human aspects of the larger project,” they write.

The study was published in Current Biology.