Published: February 25, 2011

Man-eating Lions Ate Fewer People Than Believed

Bruce Patterson, MacArthur Curator of Mammals, Integrative Research Center

Legendary "man-eating" lions of Tsavo likely ate about 35 peoplenot 135in notorious attacks

SANTA CRUZ, CA--The legendary "man-eating lions of Tsavo" that terrorized a railroad camp in Kenya more than a century ago likely consumed about 35 people--far fewer than popular estimates of 135 victims, according to a new analysis by researchers at the University of California, Santa Cruz. The study also yields surprises about the predatory behavior of lions.

Despite the notoriety of the attacks--the harrowing nine-month saga has been the subject of three Hollywood films, and the lions remain a popular exhibit at The Field Museum in Chicago--the number of victims has been a matter of dispute. The new study, "Cooperation and Individuality Among Man-Eating Lions," appears in the November 10 issue of the Proceedings of the National Academy of Sciences, where it was featured on the journal's cover. The research utilized a sophisticated stable-isotope analysis to investigate this vexing question.

By analyzing samples of the hair and bone of the lions, researchers were able to estimate that one lion likely ate 11 humans and the other consumed 24 people during the animals' final nine months. Both lions were shot and killed in December 1898 by Lt. Col. John H. Patterson, a British officer and engineer hired to restore safety in the region. Many years after, Patterson, who gained great notoriety for the feat, claimed the lions had killed 135 people--far more than the Ugandan Railway Company's records of 28 victims.

"This has been a historical puzzle for years, and the discrepancy is now finally being addressed," said Nathaniel J. Dominy, an associate professor of anthropology at UCSC. "We can imagine that the railroad company might have had reasons to want to minimize the number of victims, and Patterson might have had reasons to inflate the number. So who do you trust? We're removing all those factors and getting down to data." Dominy and lead author Justin D. Yeakel, a doctoral candidate in ecology and evolutionary biology at UCSC, collaborated on the project with Bruce D. Patterson, MacArthur Curator of Mammals at The Field Museum (no relation to John H. Patterson).

To investigate each lion's lifetime dietary patterns, Yeakel analyzed samples of their bone collagen and hair keratin that were provided by the Field Museum. He then compared that data to the isotopic signatures of the lions' presumptive prey, including modern grazing and browsing animals, and humans. Human samples were obtained from the remains of Kenya's Taita population that were gathered by anthropologist Louis Leakey during his famous East African Archaeological Expedition of 1929.

The results suggest that during the final months of what John Patterson described as the lions' "reign of terror," fully half of one lion's diet consisted of humans, with the balance made up of mid-sized grazing animals such as gazelles and impala. Strikingly, the other lion ate very few humans, subsisting instead on herbivores. That dietary disparity leads Dominy and Yeakel to infer that the Tsavo lions worked together to scatter everyone, both humans and wild game, setting the stage for one to gorge on humans and the other to feed on herbivores.

"The idea that the two lions were going in as a team yet exhibiting these dietary preferences has never been seen before or since," said Dominy.

Cooperative hunting is beneficial when lions are stalking large prey like Cape buffalo and zebra, but humans are small enough that lions don't typically need to work together to make a kill. In this case, an array of conditions may have temporarily altered the lions' behavior, including drought and disease that depleted the availability of the lions' conventional prey. In addition, large numbers of people and animals had gathered for the railroad project, and severe dental problems and a jaw injury suffered by one of the lions probably greatly inhibited its ability to hunt.

"These findings underscore the complexity of what lions are capable of doing, and the complex interplay of costs and benefits that determine the size of their coalitions," he said

The stark dietary differences highlight the importance of considering individuals within populations, said Yeakel. "In ecology, we often think of a population as being the sum of its parts, but there can be really rich things happening among individuals in a population," he said. "It's a new way of thinking about how populations work to consider how individuals affect the whole."

More than a century after the attacks, the Tsavo lions remain notorious. The grisly chapter finally ended in December 1898, when John Patterson--after nine months spent in pursuit of the animals--shot and killed one lion, then killed the second lion 20 days later. During the final three months of the nine-month siege, lion attacks were a "nightly occurrence," and work on the railroad expansion had ground to a halt as terrified laborers refused to work, said Dominy, noting that the delay prompted the first and only mention of lions in Britain's House of Parliament as members demanded an explanation for the work stoppage.

Ending the terror earned John Patterson widespread and enduring fame, but Dominy wonders if the boastful hunter might have exaggerated his estimate of victims to enhance his own reputation. "The railroad company attributed the deaths of 28 Indian nationals to the lions, and Patterson may have reasonably assumed scores of Africans were also killed," said Dominy. "But based on our statistical analysis, there's an outside chance they ate as many as 75 people. Our evidence attests only to the number of people eaten, not the number of people killed."

In 1924, John Patterson sold the hides of the lions--which he had used as trophy rugs--to the Field Museum, where taxidermists restored and stuffed the pelts and mounted a diorama that continues to fascinate museum visitors today. Patterson's 1907 book, The Man-Eaters of Tsavo, was an international bestseller when it was published, and it remains in print today.

"The fact that we can determine both the diet and the behavior of two animals killed more than a century ago is a testament to the enduring value of museum collections and the science that interprets them," said Field Museum curator Bruce Patterson. "The rather extravagant claims (Colonel) Patterson made in his book can now be pretty much dismissed."

For Dominy, downgrading the number of human victims of the Tsavo lions is the latest chapter in a legend that takes a new turn with the insights about lion predation offered by these animals. The path of human evolution has been shaped by predation, said Dominy, noting that the efficiency benefits of bipedalism are gained at the cost of speed, making humans vulnerable to quick, four-legged predators, including lions.

"In a discussion of bipedalism, Louis Leakey once said, 'People are not cat food,' " said Dominy. "But they are. This study proves that."

In addition to Dominy, Yeakel, and Bruce Patterson, coauthors on the paper are Kena Fox-Dobbs, assistant professor of geology at the University of Puget Sound; Mercedes M. Okumura, research curator in human evolutionary anatomy at the Leverhulme Centre for Human Evolutionary Studies at the University of Cambridge; Thure E. Cerling, distinguished professor of biology and of geology and geophysics at the University of Utah; Jonathan W. Moore, assistant professor of ecology and evolutionary biology at UCSC; and Paul L. Koch, professor of earth and planetary sciences at UCSC.

Release mostly written by Jennifer McNulty, UCSC.

read the PNAS article

Dominy may be reached at;

Yeakel may be reached at;

Bruce Patterson may be reached at

Bruce Patterson

I study several topics in evolutionary biology, focusing on the diversification, distribution and conservation of mammals. The breadth of my research is testimony to the facts that no interesting biological questions are ever fully answered and progress towards answering them invariably opens up a variety of others.  Curiosity, opportunity, and a bit of wanderlust have diversified my program and caused it to span two continents.


Density of terrestrial vertebrate species ( Wonder why I study tropical animals?!

For most of my career, I have used museum specimens to study the systematics and biogeography of Neotropical mammals.  Collaborating with scientists and students in Ecuador, Peru, Bolivia, Brazil, and Chile, I have worked throughout the Andes, Amazonia, as well as Atlantic, Valdivian, and Magellanic Forests. While documenting some of the world's richest and most highly endemic faunas, we regularly discover and describe new taxa of marsupials, rodents, and bats and use them in regional and continental reconstructions of phylogeny and biogeography. The program offers abundant training opportunities for American and Latin American students, both in the lab and in the field.  Beginning in 2011, I started a parallel project on the The Bats of Kenya with colleagues Paul Webala and Carl Dick.  This project is designed to document the distribution and status of more than 100 species of bats that occur in Kenya and to shed light on their ecological roles and current status.

Collecting parasites in the course of these systematic studies led to my interest in host-parasite coevolution.  Ectoparasites recovered from mammals and birds are used to reconstruct the radiation of parasite groups and to assess their distributions across hosts and geography.  These studies identify factors that govern the distribution, abundance, and host specificity of parasites.  Together with Carl Dick (until 2009 a post-doc here at the Museum, now at Western Kentucky University) and Katharina Dittmar (SUNY Buffalo), we have developed a broad range of studies on the ecology, coevolution, and phylogeny of these interesting flies.  Interest in the unstudied ectoparasite communities of African bats helped fuel our collaborations with Kenyan Paul Webala to survey the diverse bat communities of Kenya.        


A Hipposideros bat with an ectoparasitic Penicillidia bat fly

A second, derivative program focuses on host-parasite coevolution.  Ectoparasites recovered from mammal and bird specimens are used to reconstruct the evolutionary radiations of parasite groups and assess their current distributions across hosts and geography, factors governing their distribution, abundance, and host specificity.  Work on bat flies has been developed with Carl Dick (until 2009 a post-doc here at the Museum, but now at Western Kentucky University) and Katharina Dittmar (SUNY Buffalo) on their ecology and phylogeny. With NSF funding, we recently curated the world's largest collection of flies, which now guides our understanding of host associations and fuels the taxon-sampling in our phylogenetic work (also supported by NSF). Undergrad and grad students are involved in this work in Chicago, Buffalo, and Bowling Green. Interest in the mostly unexplored ectoparasite communities of African bats helped fuel my collaboration with Kenya Wildlife Service ecologist Paul Webala on surveying the diverse bat communities of Kenya (see above). 

Photo by B. A. Harney in Tsavo, Kenya (July 2007)

A research program that I am now concluding focused on the Tsavo lions, infamous as man-eaters a century ago but more remarkable because many of them lack manes. In a series of papers, I have explored the morphology, genetics, behavior, and ecology of lions in SE Kenya with Samuel Kasiki (Kenya Wildlife Service) and Alex Mwazo (Kenyatta University), Roland Kays (NY State Museum), Jean Dubach (Loyola University), Justin Yeakel (UC Santa Cruz), and others.  Our aim has been to understand this distinctive and environmentally-plastic trait (manelessness) at genetic, hormonal, histological, anatomical, and behavioral levels. Concurrently, we gathered information to mitigate the impacts of lion depredations on livestock to ensure their continued survival and the preservation of their habitats. Until 2009, this project had the help of volunteers from the Earthwatch Institute.

As detailed in Students, interactions with undergraduate and graduate students enrich, extend, and complement these studies. All four research arenas offer opportunities for student research projects and post-graduate collaborations alike.