Are Maneless Tsavo Lions Prone to Male Pattern Baldness?
Bijal P. Trivedi
for National Geographic Channel
|Updated January 10, 2005|
The male lions of Tsavo, Kenya, which gained notoriety in the late 19th century as man-eaters, are unusual for two reasons. They lack the majestic golden mane commonly associated with male lions, and they have been found to have an uncommon family life, according to a report.
"When we began this study there really was a question whether there was such a thing as a maneless lion," said Bruce Patterson, MacArthur Curator of Mammals at the Field Museum in Chicago and co-author of the study.
Maneless lions had been seen before. But a consistent study had not been done to determine whether these sightings were of adolescent male lions, which hadn't had time to grow a mane, or possibly castrated males who lost their mane within a few months.
Patterson and colleague Roland Kays, senior scientists of zoology at the New York State Museum in Albany, initiated their study in Chicago's Field Museum, where the famous man-eaters of Tsavothe two large males that killed 135 railroad workers in1898lie stuffed on display. The two lions had been shot, killed, and skinned, and lay as "trophy rugs" for 25 years, before finding their way to the Field Museum in 1924.
The curious thing about the lions was that they were maneless.
What surprised Patterson and Kays was that these man-eaters were adults, between eight and ten years old; most males develop manes by age five. Earlier studies in the Serengeti had suggested that maneless lions were "losers" or "humiliated" members of the pride. "Lacking a mane was something like a badge of dishonor," said Patterson.
Study in the Wild
Curious about the social consequences of lacking a mane, Patterson and Kay traveled to Tsavo East National Park in Kenya to investigate the plight of maneless lions.
Their hypothesis was that the prides in Tsavo East would be small because the region is very dry and food is scarce. They also expected fewer males would govern these petite prides.
Unlike the Serengeti, where the food is plentiful and the lions are relatively easy to find, the challenge in Tsavo is finding the lions. To lure them from the dense woody thickets scattered through the arid open savannas, Kays used the ultimate bait: the "plaintive bleat of a wounded baby buffalo."
While traveling in Tsavo, Kays saw a wounded baby buffalo trailing behind the herd and calling to its mother. Kays videotaped the scene which he later played over a loudspeaker system mounted on the landrover. "It was like ringing the dinner bell at Tsavo," says Patterson. The prides came right out of the undergrowth and close enough to the vehicle for the researchers to observe the tiny nicks and scratches that help distinguish one animal from another.
What the researchers saw astounded them.
The maneless lions had no trouble attracting a healthy harem of femalesthe Tsavo prides were surprisingly large, with seven or eight females, and were ruled by a single male lion. By contrast, Serengeti prides were slightly smaller, with six or seven females, and were ruled by a consortium of two to four males.
"None of the Tsavo prides had more than one male, which makes them very distinctive," said Patterson.
But the social scene gets even stranger.
It seems that there are far more nomadic males in Tsavo than have been observed in other places.
"Coalitions of three or four males live and hunt togetherthis is an alternative social structure that we have never seen," said Patterson. What surprised the scientists was that these coalitions were not able to displace the "pridemaster" and take over a pride.
The results of the study were published online on April 11, 2002, in the Canadian Journal of Zoology.
Hormones Gone Awry?
Patterson's theory is that the social structure and the absence of the mane all boils down to hormonestestosterone, to be specific. He suggests that the coalitions are transient social groups made up of adolescent males whose testosterone levels have not yet peaked.
"By the time testosterone peaks at around age six or seven, intolerance also peaks," said Patterson. This is when the coalition tends to break apart and the males go their separate ways.
Manelessness might also be due to hormone levels, Kays said. High testosterone levels inhibit hair growth in human males and leads to male pattern baldness. Similarly, Tsavo male lions may be genetically predisposed to high levels of testosterone. The high hormone levels may also explain the heightened aggressive tendencies seen in these lions.
Both authors are travelling back to Kenya this month to investigate how maneless lions in Tsavo East interact with maned lions in Tsavo West. The team will collect fecal and hair samples for DNA analyses that should reveal the family structure of lions in the area. The sample will also be used to measure hormone levels. The researchers plan to put satellite collars on lions to track where, when, and with whom the animals roam throughout the year.
Patterson and Kays' work will help determine whether the Tsavo lions are actually a genetically unique population, said John Gittleman, a biologist at the University of Virginia. "These studies are critically important for long-range conservation of the entire species," he added.
The role of the mane has never been firmly established. It was thought the manes were selected for during evolution because they attracted females, intimidated other males, and protected the neck regions during fights. But the findings in Tsavo indicate that the maneless males are certainly not starved for female attention and actually command larger prides than maned lions.
The environmental cost of having a mane in Tsavo may be greater than in other areas, suggests Kays.
It seems that "the Tsavo lions have a lot of tricks up their sleeve that will only become obvious as we study their behavior and ecology," Patterson added.
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