The Maasai people of East Africa have long lived inside bomas, family compounds made of concentric rings of acacia thorns that encircle their huts and provide protection for both humans and livestock.
But because the thorns degrade quickly in the sun, bomas are not enough to keep out animals such as lions, hyenas, and leopards, which are capable of slinking through spaces in the dried-out barrier to reach their prey. When these big cats invade the compound and kill livestock, the Maasai often turn around and kill the predators in retaliation. (Related: "Can Good Come From Maasai Lion Killings in the Serengeti?")
These killings—combined with habitat loss and lack of prey—are responsible for the dramatic decline seen in big cats, especially African lions, in the past 35 years. Up to 76,000 lions roamed Africa in 1980, a number that has been slashed by more than half, according to the U.S. Fish and Wildlife Service, to just 35,000 today. (See a photo gallery of African lions.)
But conservationists and Maasai herders may have found a solution: a fortified boma they call a "living wall." In addition to the inner ring of acacia thorns, the Maasai plant native trees that act as fence posts, which are then covered with chain-link fencing that makes it impossible for predators to squeeze through.
Between 2003 and 2013, trained Maasai observers recorded only two attacks on 62 "living wall" bomas in Tarangire National Park on the Masai Steppe of northern Tanzania. In other words, the structures were 99.9 percent successful at preventing predator attacks.
"This would not have worked had we not had an open stream of communication" to find out what the Maasai needed, said Laly Lichtenfeld, co-founder and executive director of the nonprofit African People and Wildlife Fund.
"It was an innovation that came up between us and our Maasai team," said Lichtenfeld, who receives funding from National Geographic's Big Cats Initiative.
"Sizable Step" Toward Saving Lions
Before the living walls were installed, large carnivores would attack livestock about 50 times a year in each of the Masai Steppe's 12 communities.
Each community would then kill six or seven lions a year. That meant an annual loss of up to 84 lions.
Strikingly, Lichtenfeld said, no Maasai killed lions, leopards, or hyenas at the 62 living wall bomas during the study period, despite the fact that the animals were still living in the habitat. (Read more about living walls in the Masai Steppe.)
This suggests living walls are "tremendously" effective in reducing both livestock attacks by predators and predator deaths at the hands of humans, said Lichtenfeld, whose analysis will appear December 2 in the journal Biodiversity and Conservation.
Experts in lion conservation agreed. (Read "Living With Lions" in National Geographic magazine.)
"This is a highly innovative piece of work, combining the best of practical actions based on meticulous evidence, using science to solve practical problems," David Macdonald, director of the Wildlife Conservation Research Unit at the University of Oxford in the U.K., who was not involved in the study, wrote in an email.
"The need for work of this combination of science and practicality has never been greater, and it offers tangible hope to resolving the urgent issues of carnivores in conflict."
Bruce Patterson, curator of the Integrative Research Unit at Chicago's Field Museum, said that he was impressed by the size and scope of the study.
"Too often, analyses of this sort are so circumscribed in time and space that they cannot represent the full range of natural variation in predator and prey densities, livestock husbandry, and weather," said Patterson, who was not involved in the study.
"Lichtenfeld and colleagues have taken a sizable step towards mitigating lion-human conflict, one needed to help foster lion conservation."
Living Walls Take Root
Lichtenfeld and her colleagues made sure before beginning the project that there was enough natural prey around for lions if livestock were no longer on the menu. (Learn how you can help protect big cats.) Only when the team found out that prey animals (such as wildebeest, zebra, and buffalo) were plentiful in this region of Tanzania did they feel confident about proceeding.
The word-of-mouth buzz about living walls is spreading to other parts of Tanzania, including the Serengeti. Currently, Lichtenfeld and her team install about 150 living walls a year, at a cost of $500 each, 20 percent of which is paid for by the community. She thinks the project has the potential to provide thousands of bomas.
"It's gotten so much steam," she said, "it's hard for us to keep up with it."
Tune in to Nat Geo WILD's Big Cat Week through December 5. Big Cat Week is part of the Big Cats Initiative, a long-term commitment by the National Geographic Society to save big cats around the world. Meet National Geographic's big cat experts in a Google+ Hangout on December 3 at 1 p.m. ET and share your thoughts at #BigCats and #GivingTuesday.