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SCIENTISTS GET EVEN CLOSER TO DISCOVERING THE MYSTERY OF THE 'MAN-EATING' LIONS OF TSAVO


by Curtis Abraham



FROM THE ARCHIVES



The two 'man-eaters' displayed in taxidermic splendor at the Chicago Field Museum



Popularized in the 1996 Hollywood film The Ghost and the Darkness, staring Val Kilmer and Michael Douglas, the legendary ‘man-eating’ lions of Tsavo, western Kenya, have passed into realms of modern folklore. More than a century later (124 years to be exact), and certainly one of the greatest wildlife mysteries of the ages, scientists continue to investigate why these lions began eating people. Numerous theories have been suggested (ironically, many of the same forces that might have drove these, and a few other African lions, to develop an appetite for human flesh continue today: habitat destruction, drought, contagious viral diseases, famine, loss of prey, and lion-human conflicts outside protected areas).


Conservation-wise, African lions are on the back foot. Panthera Leo, has already disappeared from a dozen or so African countries. Meanwhile, other populations in west and east Africa are in rapid decline. In Africa and Asian today (more irony), we humans now consume their body parts (e.g. concocting traditional medicines from their bones). Could this sad state of affairs lead today's wild lions to return to their ‘man-eating’ ways?


“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 mane-less 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.


Col Patterson's book about his adventures hunting down the Tsavo 'man-eaters'


Col. John H. Patterson



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.


(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, have been instrumental in helping to uncover the mystery behind two lions).


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.i

Having identified the lion skulls, the main focus of the research then looked at 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.


“Tooth breakage per se does not produce dietary shifts as older lions display some sort of wear or breakage to their dentition;” wrote Larisa R. G. DeSantis and Bruce D. Patterson in their 2017 paper. The pair examined the two Tsavo lions and another man-eater from Mfuwe, Zambia. 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.”


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.


Scientist also believe that the Tsavo lions might have 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, traditional cattle herders 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, a Bantu-speaking tribe who lived from Nairobi to Tsavo and north to Embu in the southern part of what was Eastern Province, are said to have died from starvation at the same time the railway was being constructed through Tsavo. During the 1860s cholera and plague brought by Swahili caravans also ravaged the region.


“although the verdict is still out, it is very probable that the Tsavo Man-Eating lions got their appetite from eating victims of famine, warfare and caravan trade,” says Bruce Patterson, MacArthur Curator of Mammals at Chicago’s Natural History Museum.


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 region of the 1890s was composed of a nearly impenetrable, thorn thicket known as ‘nyika’ - unlike the Tsavo of today that contains 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).


Tsavo's natural environment around the railway tracks, 1898



Indian Railway workers at Tsavo, 1898

Kenyan Railway workers at Tsavo, 1898



One curiosity about the man-eaters is that although the Tsavo man-eaters were male lions, they did not possess manes, characteristic of lions throughout the African continent.

In 1999, Patterson and colleague Roland W. Kays, then a post-doctoral fellow at the Chicago Field Museum, established beyond doubt that male lions in Tsavo were typically mane-less. The pair spent four months in Tsavo, systematically documenting the park’s lions and recording the conditions of the manes of males and the social groups in which they occurred.


Years later, Julian C. Kerbis Peterhans and Thomas Gnoske, collection manager in the Field Museum’s Zoology Department and a field biologist, published a landmark paper in the Journal of Zoology showing that Tsavo’s mane-less male lions, or those with delayed mane development, are the result of localized adaptations to the hot, dry climate of Tsavo.


The exact numbers of railway workers who

were killed and eaten by the two lions is also disputed. 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.


Museum Taxidemist working on the Tsavo 'Man-eaters' exhibit

Dentition of one Tsavo 'Man-eater'

Suspected cave of the Tsavo 'Man-eaters'


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 specialization on humans or human ancestors, some wildlife experts speculate, may be a long standing fallback strategy among lions.


Yet another mystery is the existence of a den, where the two man-eaters lived and perhaps finished off their human prey? If so, where was/is it located?


In April 1997, Thomas Gnoske and Julian C. Kerbis Peterhans discovered the cave that J. H. Patterson wrote about in The Man-Eaters of Tsavo. Gnoske had brought with him an enlarged copy of the original black and white photograph that Patterson took of that cave. This allowed researchers to make a positive identification since they had examined hundreds of caves during their search.


“After we found the cave, there was immediate interest by the Kenyan Government including David Western, then Director of the Kenyan Wildlife Service, journalists, documentary film makers, other biologists,” remembered Gnoske.


Patterson said the cave was filled with human remains, which he assumed were the remains of the victims of the two man-eaters. However, this claim remains inconclusive because in the year that followed, there was an attempted excavation of the cave by an American and Kenyan archeological team. However, the project failed to turn up evidence of the human remains and after a few weeks, was abandoned.


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.


Modern Tsavo Lion


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.


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