Speculators and scientists have long wondered why these lions ate humans — most lions do not. The cats inspired three Hollywood movies, dozens of academic papers and countless newspaper articles. Their bones and skins continue to provide information, in finer and finer detail. A study published Wednesday in the journal Scientific Reports took a microscopic look at the grooves on the lions' fangs. Their analysis suggests that the lions likely preferred hunting live humans because they were softer than gnawing on dead bones.
“There’s really something about 'man-eaters' that puts people in their rightful place,” said Bruce Patterson (no relation to the Lt. Col. Patterson), a co-author of the new paper and the curator of the mammal collection at Chicago’s Field Museum of Natural History. “Not at the helm but a couple of notches down.”
As a mammalogist at the Field Museum, Patterson oversees some 230,000 specimens. “Few have stories to tell that are as exciting as these two,” he said. When the museum bought the lions in 1925, the animals arrived splayed out as rugs. The rug-maker kept the cats' skulls within their skins, a fortuitous decision for researchers such as Patterson.
In 2000, Patterson's examination of those skulls showed that the dominant member of the Tsavo duo, the lion probably responsible for killing more humans, was missing several teeth. He also had a severe tooth abscess. Lions frequently break their teeth, Patterson said, if grazing animals respond to the cats' face-first lunges with hoofed kicks. But abscesses and more grievous injuries are rare. The pus pocket may have made it too painful for the Tsavo lion to subdue typical prey, an explanation that Patterson quipped was the “smoking gum.”
Even with broken teeth, lions are flexible eaters. Perhaps the Tsavo lions first had to scavenge on corpses, he suggested, and only then began to hunt the living. In 1898, bodies would have been common: First, a severe drought struck the region, killing livestock herds and herders alike. Second, a virus called rinderpest felled cattle and their wild relatives, including common lion prey such as buffalo, making the lions desperate for new sources of food. And third, the British engineers planned the railway along a caravan route that brought slaves from Uganda and the Congo to the coast. “This caravan trail would have left a steady trail of dead and dying slaves,” Patterson said.
For the most recent study, Patterson and a colleague, Vanderbilt University's Larisa DeSantis, pored over the lion teeth, analyzing their dental microstructures. The scientists compared the Tsavo lions' teeth to those of zoo lions, wild lions, cheetahs and known bone-crunchers such as hyenas.
The Tsavo lions' teeth were most similar to those of captive animals. Zoos provide lions with slabs of horsemeat or beef, Patterson said, and only rarely give the cats access to carcasses. Likewise, cheetahs, which do not eat bones, showed similar wear on their teeth to the Tsavo lions' grooves.
The analysis ruled out the hypotheses that the lions developed a taste for humans by scavenging on dead bodies, in the scientists' view. Scavengers eat the bones of bodies that are not freshly killed, either because the flesh has decayed or something else picked at it first. Lions prefer human guts, zoologists reported in 2001 in the Journal of East African Natural History, as well as “large fleshy parts, including the buttocks, thighs and arms.” As the researchers concluded in the new report, “the man-eating lions consumed softer parts of humans and other prey and did not fully consume carcasses.”
This may seem like a lot of fuss over a century-old lion lunch. But, as the researchers noted, the Tsavo tale has been hard to let go.
Craig Packer, a professor of ecology, evolution and behavior at the University of Minnesota, said part of the story's appeal was that, “It was the great white hero sort of thing.”
(Hollywood, in 1996's “The Ghost and the Darkness,” doubled the number of heroes to accommodate both Michael Douglas and Val Kilmer.)
The Tsavo lions were easily molded into blockbuster villains. They had no manes, which Patterson argued in 2006 was an adaptation for the region's exceptional heat. The lack of regal fur buttressed the impression that the lions were sinister, slinking hellcats. “The Ghost and the Darkness” screenwriter William Goldman told the Los Angeles Daily News that, “My particular feeling is that they were evil. I believe that for nine months, evil popped out of the ground at Tsavo.”
Packer, one of the world's foremost lion experts, has little time for occult explanations. “It’s not like there’s a mean, mystical, nasty lion that decides to eat mankind,” Packer said. “No. No, they’re just hungry.”
Packer said he was impressed by the level of scientific detail that the new study extracted from the Tsavo teeth. But he maintained that there were two major reasons the lions hunted humans: a lack of prey because of the cattle plague, plus an unusual influx of new food — exposed humans along the railway.
“It’s not unique for lions to attack people. It's a problem for the reality of lion conservation,” he said. By way of parallel example, Packer pointed to a contemporary case in Tanzania, where lions continue to attack humans. In a 2005 Nature study, Packer and his co-authors tallied nearly 600 deaths in the country since 1990. Lions were scraping by in a region converted to agriculture, mainly on a diet of bush pigs, Packer said. The bush pigs also proved to be a major nocturnal pest, so Tanzanian villagers slept in temporary structures in their fields to guard them against the pigs. And then the lions figured out, “Oh, right, I can eat this,” as Packer put it, and the attacks began.
Opportunity alone is not enough. Packer recounted an anecdote of a man who, a few years ago, went camping in the Serengeti, where there are essentially no instances of lions that eat people. The camper insisted on sleeping with his head outside of the pup tent, to watch the stars as he fell asleep. As far as anyone could tell, Packer said, simple curiosity motivated the lion that wandered by. The big cat started to sniff the strange human head. The man woke up and panicked. The lion spooked.
“In that case the human zigged when he should have been very still,” Packer said, “and the lion crunched him.” But the camper wasn't devoured. A cat, even one that makes a fresh kill, won't become a people-eater unless it lacks food.
“The key,” Packer said, “is you don’t want to have vulnerable people around hungry lions.”