The herders kill lions and other predators that go after their livestock. Frank's project promotes livestock-protection techniques and works with another group that compensates herders for livestock lost to predators.
The program was successful in northern Kenya. But after nearly three years, Frank is pessimistic about the prospects for the program in southern Kenya.
"I think it is way too late for a nice education program or happy talk about building up tourism," he said.
"I'm convinced only serious law enforcement [will work], but I don't think we will see that."
Killing lions deliberately is illegal in Kenya, according to Wilson Korir, an assistant director for the Kenya Wildlife Service, the agency responsible for enforcing wildlife protection laws.
Korir says the agency is enforcing the law and taking steps to reduce conflicts between humans and wildlife, which increase during the spring rainy season.
In the spring the lions' wild prey often migrate from wildlands to adjacent ranches, he explains. Lions follow, and some subsequently prey on domestic livestock too.
"This brings about the conflict," Korir said in an email.
In March and April this year, he adds, local communities lost 26 cows, 50 goats, and 4 donkeys. The recent lion killings, he says, are a reaction to these losses.
"We believe these killings are illegal, and as a result we did make arrests of nine [young Maasai] suspected to have participated in these illegal acts, and they have already been charged before a court of law," he said.
Frank said the law is being enforced ineffectively. Most who are arrested are let out on "trivial" bail or bribe a judge to drop the case, he said.
"If there were real penalties to killing a lion, this thing could be turned around," he said.
Craig Packer is a biologist at the University of Minnesota in St. Paul. He agreed that better law enforcement is needed. But he added, "it might not be enough."
According to Packer, who studies lions in Tanzania, economic uncertainty and political instability in Kenya have left many people disgruntled. These issues must also be addressed, he said.
"Lion-killing becomes a form of political protest when local communities feel that the authorities value wildlife more than people," he said.
March, April, and May are the height of the rainy season in Kenya.
During these wet months Maasai herderswho travel great distances to graze their cattle during the dry seasonare in their villages, according to Hazzah of the University of Wisconsin.
This is when young Maasai men gather for traditional lion hunts, called olamayio. These hunts are what Hazzah and colleagues have witnessed over the last few weeks around Amboseli National Park.
"What's happening today is a domino effect," she said. "One group of warriors kills a lion, [and] then other warriors hear about it and also want to take part to prove themselves to their community."
Berkeley's Frank explained that the tradition of killing lions to prove manhood is centuries old. But there used to be more lions and fewer warriors.
Complicating matters, Hazzah says, within the past decade young Maasai men have become more independent. They tend to ignore their elders, leading to a "breakdown in traditional norms, which is the backbone of Maasai society."
Changing social dynamics have also ratcheted up pressure on the lions by eroding another traditional manhood rite: stealing cattle.
For the Maasai, cattle are the currency men use to purchase wives. In years past, warriors would raid cattle from other tribes, occasionally killing each other in the process, Frank said.
But the Kenyan government has successfully enforced laws against cattle raids, largely bringing a halt to the practice, Frank said.
"Now that cattle-raiding is no longer available to them, if young men want to impress a girl, all that's left is to kill the lions," he said.
Compounding the surge in lion killings by young warriors is the increased use of cheap and effective poisons to kill the predators, according to Frank.
Traditionally, herders in Africa graze their livestock during the day. At night the men put the animals in corrals to protect the beasts from lions and other predators.
Frank's lion-conservation projects encourage herders to build more effective corrals. In exchange, the herders are compensated when lions kill their livestock.
Conservation has been successful on the commercial ranges of the Laikipia region in the north. But Frank says poisoning lions is still commonplace in the Amboseli region.
"It seems there's a whole new attitude of, Why bother with the hard work of herding if we can just poison off predators and get on with life?" he said.
Seamus Maclennan, a biologist with the Kilimanjaro Lion Conservation Project, said in an email, "Access to inexpensive, loosely controlled deadly poisons has certainly done massive damage to carnivores in Kenya."
For the past few years, however, he added, "spearing seems to be the most frequent method of killing lions."
Once the lions are gone, the University of Wisconsin's Hazzah says, the Maasai may begin killing other livestock predators such hyenas and leopards.
Though killing these animals isn't a traditional ritual, they are sometimes killed in retaliation for taking livestock, she adds.
"If [the Maasai] are not going to be reprimanded for killing the lions now, they will feel [no reason] to keep other predators around in the future," she said.
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