If I were to hazard a guess as to one of your worst nightmares, it would be being eaten alive by a wild animal. I won't blame you if it is. For some construction workers building the Kenya-Uganda Railway in Tsavo in 1898, it was a reality.
For nine months, their campsites were plagued by a pair of prolific man-eating lions: "Ghost" and "Darkness". They sound like they could be two Evanescence songs. Except it wasn't peoples' heartstrings they were pulling.
For nine straight months, the expansion of the British Empire – one of the wealthiest and most powerful at the time – was halted by two wild animals in Kenya. Embarrassment comes in many forms.
Together, they killed somewhere between 35 and 135 people (estimates vary). Between March and December, they somehow moved through all barriers and evaded all traps. From thorny bush walls, known as bomas, to even a baited, empty railroad car. Safe to say these cats had more than nine lives.
Besides their cunning and thirst for blood, there was something else that made them history's most infamous wild lions. They didn't have manes.
It turns out most lions in the Kenyan region of Tsavo lack manes. The reason has remained largely a mystery since it was documented by British colonel John Henry Patterson. He did what no man was able to: slay the man-eaters and save the face of the British Empire.
A weak/absent mane isn't the only distinctive feature these lions have. They "tend to be much bigger and much more aggressive than the lions found elsewhere", said Kenya Wildlife Service researcher Dr. Samuel Kasiki. Aside from these few differences, they're (at least appearance-wise) like any other lion.
In a survey conducted by Bruce Patterson (no relation to John) and published in the Canadian Journal of Zoology, five prides were documented in Tsavo East National Park. A mean of 7.4 resident lionesses was calculated for each; in each of the five prides, there was one adult male.
Anywhere else in Africa, a pride would be governed by two or more males, but not in Tsavo. The number of females, however, was "large (mean 7.4) and comparable with what has been documented in the Serengeti". The Serengeti itself, meanwhile, had a mean of only 6.4.
I say "only", but seven female partners are still beyond the imagination for the majority of human males — myself included. Even if one of them has a 0.4 portion of her body.
Also unlike other lions, those in Tsavo seem to be more family-focused. Kind of ironic given there's a thriller based on the two man-eaters from 1898. Nonetheless, they did various activities throughout the survey. These included hunting, interacting with females, mating, playing with cubs, scent-marking, and territory patrol. Busy boys.
In an average pride, the lionesses will do the literal lion's share of the hunting. Sometimes over 90%. Other than nomads (the lion equivalent of bachelors who are also drifters) it's rare to see a male on the hunt. The ones in the survey were, though.
Tsavo comprises two separate parks: the Tsavo East and Tsavo West National Parks. The landscape is often described as hot and dry. The average daytime temperature is about 31 °C (or ~88 °F if you're an American reading) for Tsavo East and 29 degrees °C (~84 °F) for Tsavo West.
Annual rainfall is around 25 cm (~10 inches) in Tsavo East; 45 cm (~18 inches) in Tsavo West. For comparison, the UK had 124 cm (~49 inches) in 2021. Then again, it is the UK: a country where you're taking a gamble every time you leave your house without an umbrella.
Within Tsavo East, the northern part is primarily woodland dominated by Acacia and Commiphora trees. South of the Galana River, elephants and wildfires have demolished most of the trees and created open grassland with thorn bushes.
Meanwhile, Tsavo West has a greater variety of habitats. Most of the northern part is made of acacia bushland and lots of rocky outcroppings too. In the southern part, there's open grassland. A section of Lake Jipe, which is surrounded by swamps, is located within the park as well.
With regards to the lack of manes, there are currently three main established hypotheses that try to explain it.
The first one suggests lions in Tsavo delay mane growth, or just never grow them at all, to cope with the skin-searing temperatures. This seems plausible, but the Kalahari Desert (where it reaches 40 °C on summer days) is home to a lion subspecies that has huge, jet-black manes.
The second suggests the thorny plant life of Tsavo means moving around with a large, thick mane is like walking through barbed wire in a woolly jumper. As annoying (and painful) as that may be, maneless lions have been seen in open grasslands that don't have any thorn bushes.
The third suggests Tsavo lions – similar to a regular steroid taker – have unusually high levels of testosterone. That explains their equally heightened aggression. High testosterone levels are thought to cause patterned baldness in humans. The lions could be experiencing the same effects.
However, when male lions get castrated or damage their (*cough cough) equipment, they lose their ability to produce testosterone and often lose their manes. For all male animals (that includes humans), fertilising females is their goal in life. These lions can't achieve it anymore. I send my condolences to them.
In the Serengeti National Park, leading lion experts Dr. Craig Packer and Peyton West from the University of Minnesota performed a field experiment. To say this field experiment was creative would be an understatement.
They set up four life-sized lion dummies (which were purposefully custom-made by a toy factory) with detachable mane-wigs to record how the locals would react. West even claimed the dummies "arrived in their own private jet". I promise I'm not making this up.
After five years, the results became clear. Females prefer males with darker manes than lighter ones because a darker mane is a sign of high levels of testosterone. This might make them better at defending their prides and territories. Unsurprisingly, the dummies with dark mane-wigs were quite popular.
A big, black mane is an advantage for lions in the Serengeti and elsewhere; not so much for those in Tsavo. Because prides there are relatively large, they have to hunt the bigger prey species of Tsavo's ecosystem to feed all those hungry mouths.
According to an isotopic analysis performed by Justin Yeake, the diet of modern Tsavo lions is almost entirely made up of large grazers such as buffalo, waterbuck, and zebra. These are big and potentially dangerous herbivores that lions prefer to hunt in groups to increase their chances of success.
So instead of staying behind to babysit the cubs like in other lion prides, the males in Tsavo regularly accompany the females and provide them with extra muscle.
They can't do that if they're wearing a built-in billboard that screams: "Hello there! My wives and I are right here in this grass. Is it ok if we hunt you?"
That's what a big, black mane is to them and their prey amidst a background of greens, reds, and/or yellows. So they just evolved to lose the mane. It's understandable because if I had to choose between going bald and starvation, I think I'd choose the first too. Maybe.
This is a guest post by David Duarte Crespo, a Portuguese college student studying his third year of an Animal Management course in the United Kingdom.
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