Scientists get ever closer to discovering the mystery of 'man eating lions'

| 12th April 2018
Two lions

The man-eating lions of Tsavo in the Field Museum of Natural History.

Ogeto Mwebi, a senior research scientist at the Department of Zoology of the National Museums of Kenya and Nduhiu Gitahi, the chief technologist at the Department of Public Health, Pharmacology & Toxicology based at Nairobi University are attempting now to uncover the mystery behind two man eating lions from more than a century ago. CURTIS ABRAHAM investigates

Tsavo’s lions - like most lion populations across the African continent - are in trouble. A century ago, there were an estimated 200,000 lions roaming the African wilderness.Today, there are only 20,000 lions left in the wild...

“In the whole of my life I have never experienced anything more nerve-shaking than to hear the deep roars of these dreadful monsters growing gradually nearer and nearer, and to know that someone or other of us was doomed to be their victim before the morning dawned.”

So wrote Lt. Col. John Henry Patterson in his 1907 book, The Man Eating Lions of Tsavo, a spine-chilling account of a pair of maneless male lions who reportedly killed scores of railway workers during a nine-month reign of terror near the Tsavo River.

The episode described took place during the construction of a railway bridge over the Tsavo River in 1898 and ended when the lions were killed by Patterson, an Anglo Irish soldier commissioned by the Uganda Railway committee in London to supervise the construction of the bridge.

Un-natural appetite

More than a century later, scientists and wildlife experts are continuing to investigate why these lions switched from their traditional prey and began eating people.

In 1998, the centenary year of the Tsavo man-eater’s reign of terror, scientific investigation into answering this mystery began with the collaboration of the University of Chicago’s Field Museum, where the lions are currently on display, the Kenya Wildlife Service (KWS) and the National Museums of Kenya.

One possible explanation could be that the Tsavo lions developed a taste for humans after being 'provisioned' with dead ones. For example, a slave trade route passed through Tsavo during the 19th century and this would have contributed to a large number of abandoned bodies.

Epidemic diseases also led to high death rates of indigenous communities. During the 1860’s cholera and plague brought by Swahili caravans, transporting elephant ivory, slaves, gold and animal skins to the coast, ravaged the region, affecting ethnic groups such as the Maasai, who lived further inland.

Environmental factors could also have been a decisive factor. Drought and famine conditions in the following decades of the late 19th Century might also played a prominent role. The Mwakisenge Drought and Famine of 1897-1900 was the worst of such episodes. Thousands of Kambas are said to have died from starvation at the same time the railway was being constructed through Tsavo. 

Caravan crossing

The quest for elephant ivory during the mid to late 19th Century had virtually eliminated elephants from much of eastern Kenya, including most of Tsavo. Reduced elephant populations led to the expansion of woodlands and the reduction of grazing herbivores such as buffaloes and zebras.

The Tsavo of the 1890s was composed of a nearly impenetrable, thorn thicket known as ‘nyika’ - Uunlike the Tsavo of today with large tracts of open savanna. In this thicket environment, the Tsavo lions were able to stalk and ambush their human prey. 

The Tsavo man-eaters episode closely followed a devastating outbreak of rinderpest. This decimated countless herds of cattle, buffalo, wildebeest, and zebra- the primary prey of Africa’s lions. The epidemic would have left a low population of traditional food source for Tsavo’s lion population.

‘Man-eating' behavior, however, was not an isolated incident at Tsavo. Humans were attacked and killed by lions in the Tsavo vicinity long before the construction of the railway.

In 1886, for example, there had been an attack on a caravan crossing the Tsavo River. Such attacks have continued into modern times according to records of the Kenya Wildlife Service (experts are beginning to suspect that man-eating might have evolved into a local behavioral tradition).

Prey handling

Until the 1980s, the skulls of the our two man eating lions had not been differentiated from one another. In 1987, however, Thomas Patrick Gnoske, a zoologist at Chicago’s Field Museum of Natural History in the US, rediscovered these skulls and subsequently deduced which was the first man-eater shot by referring to J.H. Patterson's testimony.

“I was just looking through the extensive research collections in the Zoology Department’s Mammal Division, which are arranged in taxonomic order, and I came across those two skulls and immediately recognized those by date, location and the collector’s name – J.H. Patterson,”  says Gnoske.

Having identified the lion skulls, the main focus of the research then focused on the teeth of the two lions. An initial analysis of the skull and lower jaw of the first Tsavo lion (known as FMNH 23970 in Chicago’s Field Museum of Natural History catalogue) revealed that they were malformed because of a severely broken canine with an expose root (the canine teeth are used primarily for firmly holding food in order to tear it apart).

This malformation led to the remodeling of the animal’s jaws, which could have prevented the lion from efficiently killing its normal prey. 

The second lion (FMNH 23969) also had teeth and jaw damage which might have also hampered its effort to eat hard food items and/or reduced prey handling ability.

Buffalo, zebras and oryx

“Tooth breakage per se does not produce dietary shifts as older lions display some sort of wear or breakage to their dentition, says Larisa R. G. DeSantis  and Bruce D. Patterson in their 2017 paper, Dietary Behaviour of Man-Eating Lions Revealed by Dental Microwear Textures.

These researchers also examined another man-eating lion from Mfuwe, Zambia - a ten feet long mane-less lion that ate six individuals.   “However, dental disease is another matter, and incapacitation via an abscessed or a fractured mandible may have prompted the Tsavo and Mfuwe lions to seek more easily subdued prey.” 

One disputed fact of the Tsavo legend has been the exact numbers of railway workers who were killed and eaten by the two lions. In The Maneaters of Tsavo Patterson says the two lions - “prowling demons” he called them - ate 135 individuals over the course of almost one year. By contrast, railway records officially attribute only 28 worker deaths to the two lions.

In 2009, Bruce Patterson and Justin D. Yekal of the University of California, Santa Cruz, and their colleagues at the University of Cambridge examined hair samples preserved in the broken and exposed cavities of their canines. The hairs are an indication of what the lions ate. 

These investigators concluded that throughout much of its life, the second lion, FMNH 23969, had a diet similar to modern Tsavo lions and was heavily reliant on Tsavo West National Park (TWNP) grazers such as buffalo, zebras and oryx.

Lions left

Toward the end of its life, the lion continued to rely on grazing animals, although subsisted on herbivores from TWNP and Tsavo East National Park (TENP) to similar extents.

By contrast, the first lion, FMNH 23970, progressed from a diet focused on grazers to one emphasizing browsers, browser/mixed-feeders, and humans toward the end of 1898. This latter result verifies historical accounts that assigned the lion’s share of human deaths to FMNH 23970. 

The researchers estimated that over the nine-months, the first Tsavo man-eater devoured 10.5 individuals and the second lion ate 24.2 individuals, which gives a total of 34.7 humans consumed. A dietary specialisation on humans or human ancestors, some wildlife experts speculate, may be a long standing fallback strategy among lions.

Tsavo’s lions - like most lion populations across the African continent - are in trouble. A century ago, there were an estimated 200,000 lions roaming the African wilderness.

Today, there are only 20,000 lions left in the wild, according to H. Bauer and colleagues in their 2015 publication: Panther Leo. The IUCN red List of Threatened Species 2015.

Commercial trade

Lion habitats have vanished due to a rise in human population and consequently to agricultural expansion to feed more human mouths. Today, lions occupy only about eight percent of their historical range and are reported to have already vanished from 12 African countries of the 47 African countries in which they were once present.

One factor that has led to the dramatic decline in Africa’s lion populations has been the depletion of their prey through hunting. While bushmeat was once obtained primarily for subsistence in rural communities, today it is also sold commercially within African urban markets and internationally to markets in the United States and Europe.

As bushmeat hunting expands from the forests to the savannas, vast areas have been emptied of large wildlife, especially the medium to large ungulates such as wildebeest, zebra, buffalo and impala on which lions subsist.

As if that weren’t enough, a 2017 survey examining the pan-African trade in Lion parts, has highlighted “escalating and worrisome trends” that could increasingly pose a threat to the continent’s dwindling lion populations.

The African lion is the only big cat listed on CITES Appendix II, and the only one for which international commercial trade is legal under CITES.

This has resulted in the widespread trade in African Lion body parts with items and products ranging from sport hunting trophies to curios sold in the tourist trade and lion bones that is increasing in demand in countries of East and Southeast Asia where it is used in Traditional Asian Medicine (African zootherapeutic practitioners and consumers mostly use fat, claws, skin and teeth for their healing rituals).
On a more optimist note, conservation efforts in Southern Africa have had much more success. In Botswana, Namibia, South Africa and Zimbabwe, where most lions live in fenced reserves that are heavily managed, lion populations have been growing. Lions in these reserves are provided with extensive vet care and even extra prey.

This Author

Curtis Abraham is a freelance writer and researcher on African development, science, the environment, biomedical/health and African social/cultural history. He has lived and worked in sub-Saharan Africa for over two decades with his work appearing in numerous publications including New ScientistBBC Wildlife MagazineNew African and Africa Geographic.

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