Ferocity at its Finest

The Tsavo River. Running east from the border between Tanzania and Kenya, its waters are teeming with life surrounded by vast grasslands. If you were to look at photos of the region, there wouldn’t really be any particular thing that would stand out as unexpected from an African savannah. So why am I sitting here sipping my morning coffee and setting the stage for such a hum-drum mundane place?

Sometimes the most ordinary places hold extraordinary natural histories.

Tsavo River. (Image from www.tsavopark.com)

Tsavo River. (Image from www.tsavopark.com)

Men and nature must work hand in hand. The throwing out of balance of the resources of nature throws out of balance the lives of men.
— Franklin Delano Roosevelt

Flash back to the 1890s. During this time period, there was a pretty massive slave trade in East Africa. The long route of the slave trade was filled with injury, disease, and little mercy. Those who were considered too weak were abandoned to die or killed as a message to others. It was a low estimate that approximately 80,000 humans were lost each year along these routes. Coinciding with this, the British government was looking to further expand its control of African regions and developed a plan to build a railway system across modern-day Kenya to Lake Victoria. This construction brought casualties of a different kind that no one expected. Between March and December of 1898, it’s estimated that a minimum of 28 railway workers were lost in addition to over 100 slaves and African natives. The culprit?

One of the two Tsavo lions.  (Image from: Kerbis Peterhans, Julian C., and Gnoske, Thomas Patrick. (2001) The Science of ‘Man-Eating’ Among Lions Panthera leo with a Reconstruction of the Natural History of the ‘Man-Eaters of Tsavo’.) 

One of the two Tsavo lions.  (Image from: Kerbis Peterhans, Julian C., and Gnoske, Thomas Patrick. (2001) The Science of ‘Man-Eating’ Among Lions Panthera leo with a Reconstruction of the Natural History of the ‘Man-Eaters of Tsavo’.) 

Not injury or disease, but a pair of merciless and mane-less male lions.

Lions are facultative predators (like many meat-eaters), meaning that their hunting strategies and prey choices are often dependent on the circumstances. That being said, while lions have been recorded to attack humans in some parts of the world, these incidents are somewhat rare and isolated. The type of mass hunting recorded during 1898 in Tsavo, Africa is not your average scenario. So what’s the deal?

Why did this happen?

Natural historians have attempted to compile all accounts of these incidents through field journals or personal diaries and have also collaborated with museums, ecologists, and biologists to analyze history of the region, environmental conditions, and anatomy of these two hunters.

Map showing Tsavo River region in Eastern Africa. (Image from Wikipedia: Tsavo River)

Map showing Tsavo River region in Eastern Africa. (Image from Wikipedia: Tsavo River)

Just like the sleep-deprived college student who suddenly acquires a taste for coffee to survive all-nighters, (non-human) animals can also become accustomed to various types of food based on availability and necessity. As I introduced earlier, there were a lot of laborers in the Tsavo River region building this railroad system and accompanying them was a massive number of domestic livestock to feed their hungry bellies. Couple this with a massive slave trade occurring at the same time period and you can begin to see that this was not only a lot of living bodies and easy-to-snatch cattle but, as things go, also a great deal of death. To a predator, trade routes were a predictable place to find very easy dinners and for our two protagonists (arguably antagonists), this is believed to be a part of their interest in eventual hunting of humans. 

While individual lions tend to have their own food preferences, some populations have been observed to develop a behavioral tradition of hunting the same types of prey species. An example of this occurred elsewhere in Africa, where lions were seen following herds of buffalo as well as learning the patterns of individual prey. Individuals in this population were even seen ignoring other more easily-available prey in order to seek out buffalo in particular. This is believed to be learned from parents by offspring, maintaining the behavior from one generation to the next. Natural historians believe now that the habit of “man-hunting” in Tsavo probably originated years before the more infamous killings, and simply persisted through lion “culture” over time.

Lt. Colonel Patterson, who finally put an end to the man-hunting in Tsavo by killing the two lions responsible. (Image from Smithsonian Magazine online, http://www.smithsonianmag.com/)

Lt. Colonel Patterson, who finally put an end to the man-hunting in Tsavo by killing the two lions responsible. (Image from Smithsonian Magazine online, http://www.smithsonianmag.com/)

But if you’re sitting there blaming the events in Tsavo on human interference saying to yourself, “maybe they shouldn’t have been setting foot in such a wild and dangerous place…”, ecologists may insist you listen to the natural circumstances occurring at the same time.

Habitat has a lot to do with it.

Lions are ambush predators; they like the ‘sneak attack’ strategy. It’s hard to be sly when you don’t have anything to hide yourself behind. Even in the open Serengeti plains, researchers note that about 75% of lion kills occur near some sort of land cover. Prior to the events in Tsavo, the region was chock-full of elephants keeping the native vegetation in check through their natural eating habits. By the 1890s however, elephant populations were severely depleted due to the unfortunate ivory business. Without these big ol’ herbivores chowing down regularly, brush became overgrown and a dense thicket became a great place for stalking lions to make their move. So by the time the railway and slave trade were in full swing, the Tsavo lions had a perfect environment for stealing away some lives.

Example of the devastation of a cattle plague outbreak, this image from a 1986 occurrence. (Image from Wikipedia)

Example of the devastation of a cattle plague outbreak, this image from a 1986 occurrence. (Image from Wikipedia)

A common explanation of wild animal attacks on humans is depletion of their ‘normal’ prey. A historical example of this is described in an account of man-eating by lions in Uganda beginning in 1924, with more than 161 people killed just that year. A few years prior to this, a disease epidemic spread across a bunch of different prey species in the region, such as wild hogs, antelope and giraffes. To combat the risk of disease, humans killed the infected animals which severely diminished food supply for lions. You can see where we’re headed. Lions turned their attention to cattle, and subsequently to man. Similarly, the same disease (rinderpest, also called cattle plague) spread through Kenya in the 1890s and it was said that, “Never before have the cattle died in such vast numbers; never before has the wild game suffered. Nearly all the buffalo are gone.” The lions were, quite simply, hungry. 

Adapt or die.

It’s probably impossible to pinpoint a single most-important cause to what would trigger lions to turn to man-hunting. Instead, it’s valuable to consider the variety of ecological and environmental circumstances that could influence a shift like this. For the Tsavo region, the overall ecology was restructured by a change in environmental landscape, depletion of prey animals, and dramatic influx of livestock and humans. As researchers noted in a final discussion of their work:

Given the circumstances at Tsavo in the 1890s, instead of asking how so many humans could have been dispatched, we wonder why there weren’t more.
Taxidermy of two Tsavo lions as on display at the The Field Museum, Chicago, IL. 

Taxidermy of two Tsavo lions as on display at the The Field Museum, Chicago, IL. 

I wouldn't typically find myself writing about natural history, but inspiration for this post came from a personal visit to The Field Museum in Chicago, Illinois. There I stumbled upon a small but powerful exhibit of the skulls and skins of the two mane-less lions who were once a mystery. The “man-eaters of Tsavo”.

Stay hungry. It's a good way to stay ahead.

Primary Reference: 

Kerbis Peterhans, Julian C., and Gnoske, Thomas Patrick. (2001) The Science of ‘Man-Eating’ Among Lions Panthera leo with a Reconstruction of the Natural History of the ‘Man-Eaters of Tsavo’. Journal of East African Natural History 90: 1-40.