Earthwatch principal investigators announce a novel social structure among the infamous lions of Tsavo East National Park, Kenya.
Earthwatch Institute, Maynard, MA, 11 April 2002-Lions are the only truly social cats, and are well known for their prides of several related females attended by a coalition of two-to-four males. But research by Earthwatch-supported scientists in Tsavo East National Park, Kenya, has documented the only population of lions known to live in large groups attended by only a single male.
The lions of Tsavo are already famous for a run of man-eating incidents at the end of the 19th century, and are also novel for lacking the impressive mane that distinguishes most male lions. Now, in an article published online by Canadian Journal of Zoology, the first scientific peer-reviewed study of the ecology of Tsavo lions reveals that they also have a unique social system.
"Although the lion is one of the world's best-studied mammals, no one has documented undisturbed groups of seven-to-eight adult females with a single adult male," says Dr. Roland Kays, curator at the New York State Museum in Albany. He and Dr. Bruce Patterson of The Field Museum, Chicago, principal investigators of Earthwatch's Lions of Tsavo project, co-authored the article.
The scientists surveyed the lion population of Tsavo East National Park, documenting the size and composition of each group and the condition of manes on males. The five resident groups of females they documented had an average of 7.4 adult females per group, large for prides in general. However, each was attended by only one male rather than a coalition of two-to-four males, typical of large prides elsewhere.
Most of what we know about lions comes from studies conducted in the Serengeti Plains, in Tanzania, where lone males are quickly deposed by coalitions of males that rule prides in unison. But the Serengeti lion, adapted to the abundance of a rich grassland ecosystem, may not be representative of the species as a whole. In fact, the lion once ranged over an incredibly vast geographic area, from South Africa to the Balkans, from Morocco to western India. To exploit such a diverse array of habitats, lions must have adapted many different lifestyles and behavior patterns.
"How does Panthera leo behave in markedly different habitats and climates?" asks the study's co-author Bruce Patterson. "Studying lions in Tsavo indicates that the 'king of the beasts' has a lot of tricks up its sleeve that confuse and astound those who would type-cast it."
Scientists have long puzzled over why Tsavo lions are maneless, but recent research suggests that manes are a liability to survival in the hot, dry Tsavo landscape with thick, thorny undergrowth. Whatever the ultimate evolutionary purpose of manelessness, the potential mechanisms are especially intriguing because they might also explain how single male lions are able to control large prides on their own.
Both the manelessness and novel social behavior of Tsavo lions may be related to elevated testosterone levels, the authors suggest. Testosterone is thought to inhibit hair growth and cause balding on the scalp of genetically disposed human males. In addition, it is known to raise levels of aggression and is higher in territorial males than in nonterritorial males.
"Tsavo lions are thought to be especially aggressive, and high levels of male hormones may simultaneously underlie this aggression, their unique social system, and manelessness," Patterson says.
Earthwatch teams will be helping Patterson and Kays, and their colleague Dr. Samuel Kasiki of the Kenya Wildlife Service, further explore the behavior and ecology of maneless lions on Lions of Tsavo starting this summer.
Earthwatch Institute is a global volunteer organization that supports scientific field research by offering members of the public unique opportunities to work alongside leading field scientists and researchers. Earthwatch's mission is to engage people worldwide in scientific field research and education to promote the understanding and action necessary for a sustainable environment. The year 2006 marks Earthwatch's 35th anniversary.