CHICAGO -- Although the lion may once have been the world's most widespread terrestrial mammal, experts recently estimated that as few as 22,600 African lions remain – 10% of the number alive just 25 years ago.
"Most of this decline can be attributed to conflicts with an expanding human population, specifically to ranchers killing lions that attack their livestock," said Bruce Patterson, PhD, MacArthur Curator of Mammals at Chicago's Field Museum and author of a new study analyzing the lion-human conflict on the frontlines of conservation in Africa.
As the number of lions continues to dwindle worldwide and humans continue to encroach on lions' traditional territory, conservationists must seek creative ways to mitigate conflict between lions and humans over increasingly scarce resources, such as land and food, Dr. Patterson said.
"To be effective, conservation solutions must involve politics and economics, as well as biology," he added.
Just published online in the journal Biological Conservation, the study concludes that only $8,749 would be needed annually to offset the economic damage of a vigorous population of 26 adult lions inhabiting two ranches in Kenya totaling 160,000 acres. "Although such a cost is crushing to subsistence farmers in Africa, the economic losses are slight by Western standards," Dr. Patterson said.
The study analyzed 312 attacks (primarily by lions but also by hyenas) that claimed 433 head of livestock (primarily cattle) on two ranches adjoining Tsavo East National Park over the four years ending in 1999. Each year, predators killed roughly 2.4% of the herd.
The park is the home of the notorious, maneless lions known for man-eating over more than 100 years. Their story is told in Dr. Patterson's new book The Lions of Tsavo (McGraw Hill, January 2004), which Publishers Weekly calls "the definitive Tsavo lion book." This new study quantifies the cost of livestock predation by these infamous lions.
Surprisingly, the study concluded that lion attacks in this arid scrubland increase during periods of precipitation, unlike lion predation elsewhere in Africa, where lion attacks increase during dry spells. In Tsavo, dry seasons concentrate traditional prey, such as kudu and impala, near water reservoirs making them easy targets. Wet seasons, on the other hand, allow native prey to disperse and use temporary but widespread water sources. "Scattered prey are harder to hunt, prompting Tsavo lions to attack livestock," said co-author Roland Kays, PhD, and Curator of Mammals at the New York State Museum. "A hungry lion is a dangerous lion."
In contrast, scarcity of traditional prey in the Serengeti occurs during the dry season, when the migrating herds of zebra and wildebeest leave to follow the rains; livestock then become far more tempting to the resident carnivores. "This suggests that lions target livestock if native prey are inaccessible, wherever and whenever that may occur," Dr. Kays said.
The authors conclude by suggesting a way to reduce lion predation on local livestock in Tsavo: a seasonal stocking plan. By quartering livestock only during the dry season and taking them to market before the annual rains, herders could take advantage of the growth of annual vegetation but avoid the majority of recurrent losses to predators.
"Although herders are aware of this pattern, ranch managers and administrators would do well to work this information into their stocking strategies," Dr. Patterson said.
Studies in the Masai Mara and Serengeti have shown conclusively that livestock is at greatest risk in the dry season, when wildlife herds migrate elsewhere, Dr. Patterson said. But showing that the wet season is most dangerous for livestock in Tsavo underscores the ecological triggering of this event. "Even a rock-solid study for managing wildlife in one ecological setting could prove worthless if applied to another area," he concluded. "Conservation plans and management solutions must be carefully tailored to the local conditions."
To read the Biological Conservation paper "Livestock predation by lions (Panthera leo) and other carnivores on ranches neighboring Tsavo National Park, Kenya" by Bruce D. Patterson, Samuel M. Kasiki, Edwin Selempo and Roland W. Kays, visit http://fm1.fieldmuseum.org/aa/Files/patterso/Biol_Cons_2004.pdf.
For more information on Tsavo's lions, visit http://fm1.fieldmuseum.org/aa/staff_page.cgi?staff=patterso&id=308.
Materials provided by Field Museum. Note: Content may be edited for style and length.
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