Africa’s poison ‘apple’ provides common ground for elephants and livestock

Impala

The tall and bushy plant known as the Sodom apple has overrun vast swaths of East African savanna and pastureland, including parts of Kenya’s Amboseli National Park. New research suggests that certain animals, including elephants and impalas, could keep this invasive plant in check. (Photo courtesy of Rob Pringle)

AFRICAN WILDLIFE OFTEN RUN AFOUL of ranchers securing food and water resources for their animals, but the interests of fauna and farmer might finally be unified by the “Sodom apple,” a toxic invasive plant that has overrun vast swaths of East African savanna and pastureland.

Not a true apple, Solanum campylacanthum is a relative of the eggplant that smothers native grasses with its thorny stalks, while its striking yellow fruit provides a deadly temptation to sheep and cattle.

New research suggests, however, that certain wild animals, particularly elephants, could be a boon to human-raised livestock because of their voracious appetite for the Sodom apple. A fiveyear study led by Princeton University researchers found that elephants and impalas, among other wild animals, can not only safely gorge themselves on the plant, but also can efficiently regulate its otherwise explosive growth.

Just as the governments of nations such as Kenya prepare to pour millions into eradicating the plant, the findings present a method for controlling the Sodom apple that is cost-effective for humans and beneficial for the survival of African elephants, explained first author Robert Pringle, a Princeton assistant professor of ecology and evolutionary biology.

Elephants

An elephant prepares to uproot a Solanum campylacanthum plant in the upland savanna of central Kenya. Although this woody shrub is toxic to many mammal species, large browsers such as elephants can eat it, and in so doing help to reduce its abundance.

“The Holy Grail in ecology is these win-win situations where we can preserve wildlife in a way that is beneficial to human livelihoods,” Pringle said “Elephants have a reputation as destructive, but they may be playing a role in keeping pastures grassy.”

The findings are important given the threats to elephants from poaching, Pringle said. “We need to understand to what extent these threatened animals have unique ecological functions.”

Elephants and impalas can withstand S. campylacanthum’s poison because they belong to a class of herbivores known as “browsers” that subsist on woody plants and shrubs, many species of which pack a toxic punch, Pringle said. On the other hand, “grazers” such as cows, sheep and zebras primarily eat grass, which is rarely poisonous. These animals easily succumb to the Sodom apple, which causes emphysema, pneumonia, bleeding ulcers, brain swelling and death.

An unexpected feast Pringle was roughly three years into a study about the effects of elephants on plant diversity when he noticed that the Sodom apple was conspicuously absent from some experiment sites. He and other researchers had set up 36 exclosures — which are designed to keep animals out rather than in — totaling nearly 89 acres (36 hectares) at the Mpala Research Centre in Kenya, a multi-institutional research preserve with which Princeton has been long involved.

There were four types of exclosure: one type open to all animals; another where only elephants were excluded; one in which elephants and impalas were excluded; and another off limits to all animals.

It was in the sites that excluded elephants and impala that the Sodom apple particularly flourished, Pringle said, which defied everything he knew about the plant.

“I had always thought that these fruits were horrible and toxic, but when I saw them in the experiment, I knew some animal was otherwise eating them. I just didn’t know which one,” Pringle said. “The question became, ‘Who’s eating the apple?”

Using the exclosures, Pringle and his coauthors documented the zest with which wild African browsers will eat S. campylacanthum. Pringle worked with Corina Tarnita, a Princeton mathematical biologist and assistant professor of ecology and evolutionary biology, as well as with collaborators from the University of Wyoming, University of Florida, University of California-Davis, Mpala Center and University of British Columbia.

The researchers specifically observed the foraging activity of elephants, impalas, smalldog- sized antelopes known as dik-diks, and rodents. Using cameras, they captured about 30,000 hours of foraging, and discovered that elephants and impalas were the primary eaters of the plants.

There is a catch to the elephants’ and impalas’ appetite for the Sodom apple: When fruit goes in one end, seeds come out the other. Though some seeds are destroyed during digestion, most reemerge and are potentially able to germinate.

Pringle and Tarnita developed a mathematical model to conduct a sort of cost-benefit analysis of how the Sodom apple’s ability to proliferate is affected by being eaten. The model weighed the “cost” to the plant of being partially consumed against the potential benefit of having healthy seeds scattered across the countryside in an animal’s droppings.

While elephants ate an enormous amount of Solanum seeds, they also often destroyed the entire plant, ripping it out of the ground and stuffing the whole bush into their mouths. The model showed that to offset the damage an elephant wreaks on a plant, 80 percent of the seeds the animal eats would have to emerge from it unscathed. On top of that, each seed would have to be 10-times more likely to take root than one that simply fell to the ground from its parent.

Impalas, on the other hand, can have a positive overall effect on the plants, the researchers found. Impalas ate the majority of the fruit consumed — one impala ate 18 fruit in just a few minutes. But they do not severely damage the parent plant while feeding and also spread a lot of seeds in their dung. Of the seeds eaten by an impala, only 60 percent would need to survive, and those seeds would have to be a mere three-times more likely to sprout than a seed that simply fell from its parent.

“A model allows you to explore a space you’re not fully able to reach experimentally,” said Tarnita, who uses math to understand the outcome of interactions between organisms. “This model helped us conclude that although it is theoretically possible for elephants to benefit the plant, that outcome is extremely unlikely.”

The study was published in the June 22, 2014, edition of the Proceedings of the Royal Society B. The work was supported by the National Science Foundation, the National Sciences and Engineering Research Council of Canada, the Sherwood Family Foundation, and the National Geographic Committee for Research and Exploration.

–By Morgan Kelly

Activism Shapes Africa Scholar

Leonard Wantchekon

Princeton Professor of Politics Leonard Wantchekon has built upon his past as a political activist in the West African nation of Benin to forge an academic career focused on studying — and working to shape — governance and institutions in Africa. (Photo by Denise Applewhite)

Leonard Wantchekon’s education began  as a young child in his home village of Zagnanado, in the West African nation of Benin, where elementary school classes gave way to long soccer games and evenings of storytelling by aunts and uncles whose tales became informal history courses.

He left village life behind in a search for academic success that took him to the nation’s most populous city, Cotonou, to the National University of Benin to study mathematics, and eventually to North America and Princeton.

During his student years in Benin, Wantchekon became a pro-democracy activist. Planning meetings became his classes, fellow activists his classmates and acts of protest his final exams. Through the 1970s and ’80s he rose to a prominent place in the opposition that helped hasten the end of the oppressive regime of Mathieu Kérékou.

“All the time I tried to be two different persons in one,” Wantchekon said. “On the one hand I wanted to be the next big thing in academics in Africa. I wanted to be a top mathematician and was very ambitious, driven and enthusiastic. … At the same time, I was an equally ambitious pro-democracy activist. I was at the center of a social movement that was pushing for major political reforms in Benin.”

His twin paths of academic study and political activism frequently diverged and intersected until a morning in December 1986, when he escaped across the border into Nigeria following 18 months of incarceration as a political prisoner and three months on the run from authorities.

“It was — or rather, I was determined to make this — the dividing line between my past and my future,” Wantchekon wrote about that moment in his autobiography Rêver à contre-courant (Dreaming Against the Grain), published in French by L’Harmattan in 2012.

A quarter-century after leaving his home country, Wantchekon has built upon his remarkable past to forge an academic career focused on studying — and working to shape — governance and institutions in Africa.

He has emerged as one of the rare political scientists who works directly with politicians, using their campaigns as laboratories to study how best to engage voters on policies. He also studies how the benefits of education spread through a society, using his home village as one of the study sites. And he’s hard at work on his most ambitious project, establishing a graduate school and center for social science research in Benin.

“We shouldn’t underestimate how crucial it is that ideas that will help Africa develop have to come mostly from Africa and have to involve more Africans,” said Wantchekon, who joined the Princeton faculty in 2011 as a professor of politics and associate faculty member in the economics department. “This, of course, cannot happen overnight. So we need to set up great institutions of higher education with the hope that, over time, we develop enough talent to make a difference.”

Political campaign as laboratory

In Benin, Wantchekon is experimenting with ways to engage voters using the nation itself as a laboratory. “As a researcher and someone who has political experience, I’m interested in the following question: How can a candidate best communicate a policy platform to the electorate that is both good for the country and can help the candidate win?” Wantchekon said.

Town hall meeting

In his research on engaging voters, Wantchekon compared the effectiveness of two campaign strategies, a town-hall meeting versus a large campaign rally. He found that the town-hall meeting is more effective at getting people to vote for the candidate, and it was far more cost effective. (Photo courtesy of the Institute for Empirical Research in Political Economy, Benin)

With the cooperation of the candidates and funding from the International Development Research Council of Canada (IDRC), he is evaluating the effectiveness of two campaign techniques: town-hall meetings focused on issues versus the usual large and costly rallies that emphasize financial incentives for voters.

Wantchekon found that town-hall meetings are more effective than rallies both in terms of getting people to turn out to vote and getting them to vote for the candidate. “Not only are the people more informed,” he said, “but those who attend share what they have learned with others.” Some of the project results were published in the October 2013 issue of the American Economic Journal: Applied Economics. He completed a similar experiment in the Philippines earlier this year with support from Princeton’s Mamdouha S. Bobst Center for Peace and Justice, and is awaiting the results.

His next project is to explore the conditions under which holding primary elections within political parties, as is done in the United States, could encourage candidates to develop more thorough expertise on policy areas. “Competition between two candidates from the same party, running on the same platform, I think will encourage candidates to go deeper into the issues with the voters,” Wantchekon said.

Peter Buisseret, a Ph.D. student studying comparative politics, is collaborating with Wantchekon on this work. “Leonard is enormously enthusiastic about the projects we work on together, and also my own work,” Buisseret said. “As a co-author, he is truly collaborative: I feel very much an equal in the projects we work on, but at the same time I recognize how much intellectual and professional benefit I get from working with someone with his experience and knowledge.”

Wantchekon said his experience in graduate school shapes the way he relates to students. After fleeing Benin, he found his way to Canada, where he earned master’s degrees in economics from Laval University and the University of British Columbia.

In 1992, he went to Northwestern University, where he earned his doctorate in economics. But the transition to the American academic system — and an environment where only English was spoken — was difficult. He overcame the challenges, though, and secured a position as an assistant professor of political science at Yale University and later on the faculty of New York University.

Far-reaching benefits of education

Wantchekon’s experiences spurred him to explore how education has benefited people within villages and across generations in Benin, a country that experienced Western colonization. When Benin, then known as Dahomey, was colonized in 1895 by France, Catholic missionaries began setting up schools throughout the region. The missionaries’ goal was religious conversion, Wantchekon said, while the colonial government aimed to train local people to work as translators, nurses, accountants and security guards.

Colonial school 1936

Wantchekon studies the benefits of education on the income levels of descendants of the first students of missionary schools in Benin. One such school shown above in 1936 operated in Wantchekon’s home village, Zagnanado. (Copyright African Missions)

Using colonial archives, school rosters and oral histories, and with financial support from IDRC, Wantchekon identified 240 of the first students to attend school in the early 1900s at four sites in Benin. He noted that these students were not smarter or wealthier than the average Benin child but merely were fortunate to live near a school, so they can be thought of as randomly selected and representative of the population. He compared each group of 60 students to a representative sample of children from a village that lacked a school.

He found that the educated individuals experienced better incomes and living conditions. For example, only 14 percent of the educated students become farmers, whereas farming was the primary occupation among the uneducated (about 80 percent). He also found that the educated were more likely to have electricity and running water in their homes and to own a bicycle, motorcycle or car.

Wantchekon also found lasting effects that went beyond the individuals who received education. The children of the first students exhibited better outcomes, as might be expected, but what is particularly striking, Wantchekon said, is that the children of uneducated parents living in villages with schools did markedly better than descendants of uneducated parents in villages without schools.

“What I draw from this is the importance of aspiration,” he said. “When you see someone who makes it, he or she is your reference point, and you want to make it too. This is a very important finding for education policy. It is how you use the success of a few to encourage the success of many.”

Wantchekon said his findings resonate with his own experience. His mother, who was mostly uneducated, would show him pictures of his successful and educated uncle and urge her children to be like him. Of the children he went to school with in the village of Zagnanado, 10 others have earned Ph.D.s. “Entire villages in Benin have been completely transformed by education,” he said.

With a small team of students sponsored by Princeton’s Health Grand Challenge program, Wantchekon is now exploring whether the beneficial effects of education have continued to spread to the grandchildren of Benin’s first students in an era of increased competition for jobs.

Returning to Benin

Wantchekon isn’t just studying Africa’s past and present. He’s working to shape its future as founder of the African School of Economics (ASE), which is set to open in Benin in fall 2014. The goal of the ASE, Wantchekon said, is to create a center of excellence for social science research in Africa.

African School of Economics

Wantchekon is working to establish the African School of Economics (ASE), whose offices and a related organization, the Institute for Empirical Research in Political Economy, are currently housed in the building (top) in Abomey Calavi, Benin. Plans for a new ASE campus, pictured in the architectural renderings (bottom), are underway. (Photo courtesy of Serge Boya; architectural renderings courtesy of ASE)

The school, which has its roots in a research institute Wantchekon established in Benin in 2004, has received funding from the Women for Africa Foundation and SES, a satellite company based in Luxembourg, and is scheduled to open with about 300 master’s degree students.

“I’ve always thought that the way to promote social science research in Africa is to have a better African representation in social science research

in Africa,” Wantchekon said. “We need to solve development problems on the continent through original thinking and indigenous generation of knowledge.”

The ASE will bring together students and faculty from Africa and beyond with an academic focus on informing social science within the context and history of Africa. Classes will be taught in English. The school’s structure and curriculum have been established. The design of the school, to be based near the city of Cotonou, is nearing completion.

The ASE is also pursuing academic partnerships with universities around the world that he hopes will lead to a free flow of students, faculty and ideas. Earlier this year, Princeton announced a partnership involving Wantchekon and the University of São Paulo, the Center for Teaching and Research in Economics in Mexico, and the Institute for Empirical Research in Political Economy in Benin. As part of this program, ASE hosted a summer school and conference involving 12 graduate students from Princeton and 10 from African universities.

“One of the things the University is very excited about in terms of this initiative is the opportunity our faculty will have to collaborate with scholars in Western Africa and possibly in other countries in sub-Saharan Africa later,” said Diana Davies, vice provost for international initiatives. “Also, this allows us to engage in the activity of capacity building and helping to build up the next generation of scholars in Africa, which is something that’s very important to us.”

“Africa is part of the University’s larger internationalization effort,” said Jeremy Adelman, Princeton’s Walter Samuel Carpenter III Professor in Spanish Civilization and Culture, professor of history and director of the University’s Council for International Teaching and Research. “But the strategy has to be adapted to Africa. Figuring out how it’s going to work in Africa requires working with Africans.”

Wantchekon knows that much work remains to reach his goals for the ASE. “I am really determined to get there,” he said. “ASE enables me to nourish big ambitions and dreams for Africa while being among the best academics in America.”

By Michael Hotchkiss