for National Geographic News
Attacks by African lions on people and livestock have been in the news lately, but on the whole humans present a much greater threat to Africa's lions than the lions do to humans.
South Africa's free-ranging lion population, an estimated 2,700 animals living mostly in the ecosystem surrounding Kruger National Park in the northeast corner of the country, is among those at risk.
One possible threat is bovine tuberculosis, a disease probably introduced to South Africa through domestic cattle brought in by European settlers at the end of the 18th century.
The disease also afflicts animals in the Serengeti grasslands and woodlands in northern Tanzania and southern Kenya. But according to Craig Packer, professor of zoology at the University of Minnesota, TB isn't as important an issue there.
"While it seems that TB is a worse problem in Kruger than elsewhere, it is still not clear that the disease is as devastating as people originally claimed," he said. "While we still have TB in Tanzania, it isn't a problem that we worry much about."
Dewald Keet, the chief veterinarian at Kruger National Park, does worry. He said that bovine tuberculosis is an ever-increasing threat to Kruger lions. But because TB is increasing at a slow rate, people may have the mistaken impression that it has stabilized.
"Nothing is being done to control the disease except research," he said. According to Keet, the prevalence of the disease in lions in the southern half of the park varies between 48 percent and 78 percent.
He explained that lions first contracted the disease when eating infected buffalo carcasses, and the southern region of the park is where TB prevalence is highest in African buffalo. Lions in Kruger are also infecting each other through biting and aerosol transmission, Keet said.
About 25 lions die of TB every year in Kruger, but even more important is the effect of the disease on lion social behavior. Males are weakened by the chronic disease, and this, Keet said, leads to "faster territorial male turnover and consequent infanticide, eviction of entire prides, and a decrease in average longevity."
Hunting lions is still legal in South Africa. According to Karyl Whitman, a graduate student in the Department of Ecology, Evolution, and Behavior at the University of Minnesota, "nearly all of the hunting is conducted on private ranches, and thus on small 'manicured' populations as opposed to 'wild' viable populations."
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