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Lions in the queue for food

The number of lions in Kenya is decreasing alarmingly, due partly to the encroaching cities and the development of the countryside. Together with local scientists and inhabitants, Leiden biologists are studying how this decline can be halted. ‘Lions are cleverer than we thought.’

Inhabitants of the suburbs of Nairobi often get the shock of their lives: every year between the streams of cars a huge lion will make its appearance. And, given the resulting commotion, these 3200-kilo lions find themselves hemmed in by the cars. In Kenya’s capital Nairobi, this is a more frequent occurrence than it may seem, Leiden Professor of Environmental Biology Hans de Iongh, who also has an appointment in Antwerp, explains. With its rapidly increasing population, the capital city is spreading out towards the borders of Nairobi National Park; at just 117 sq.m., the part is relatively small. As a comparison, the Veluwe Park in the Netherlands is around 1,000 sq.m.

The partly enclosed Kenyan park is open on the south side so that the wild animals, such as zebras and giraffes are not completely restricted in their search for food. But the same also applies to the 35 to 40 adult lions that regularly go hunting outside the park – with all the consequences this entails. Last year park rangers shot an aggressive lion dead outside the park because it was fighting with another lion, and causing some concern. Neighbouring cattle farmers sometimes kill lions if they attack their cattle or sheep. And the lions in the traffic? They often return to the park of their own accord, but there are also occasions when they have to be anaesthetised before they can be removed, or they are even killed. 

Restricting lions’ freedom

The Kenyan lion population has declined alarmingly over the past twenty years: from around 2,700 lions at the turn of the century that number now stands at around 2,000. The Kenya Wildlife Service is applying compensation measures and issuing advice to the local population to stop the lions running completely free. This Kenyan government organisation has also called on the help of Leiden researchers. PhD candidates and students have been conducting research here for over ten years, supervised by Professors of Environmental Biology Geert de Snoo and Hans de Iongh. De Iongh works at the Institute of Environmental Sciences, part of Leiden’s Faculty of Science, and De Snoo is dean of the same faculty. The researchers are studying the behaviour of the lions and whether their feeding patterns are changing under the influence of climate change.

One of the Leiden PhD candidates is Kenyan Francis Lesilau, Head of Security at Nairobi National Park (see box). He is researching how farmers can protect their animals against lions, and conversely, how lions can be protected against people. The conflicts between humans and lions are unfortunately increasing, Lesilau explains by phone from Nairobi. Beside  population growth, climate change also plays a role: the increasing drought is drawing the animals further away in their search for food, which means that animals of prey, like lions, have to travel many kilometres. ‘For them, the bomas, the enclosures where the cattle are kept overnight, are rather like attractive shopping centres where they can do some food shopping,’ De Iongh explains. Lesilau understands the fear and anger of the cattle farmers. ‘The cattle are their only asset as well as their food.’ But he also wants to protect the lions so that they don’t become extinct in the region.

As Head of Security, Lesilau patrols Nairobi National Park almost every day. By chance, he often witnesses interesting incidents. He has twice seen a lioness pull a tranquiliser dart out of her rear paw.
As Head of Security, Lesilau patrols Nairobi National Park almost every day. By chance, he often witnesses interesting incidents. He has twice seen a lioness pull a tranquiliser dart out of her rear paw.

Disco lights

Lesilau’s PhD research further builds on an inventive discovery dating from 2013 by the then 13-year-old cattle hand Richard Turere. As the son of a Masai cattle farmer, it was his job to protect the family’s cattle. After a lion had forced its way into the enclosure and killed a cow, Richard devised a deterrent system made up of flashing lights on the boma. It worked extremely well; the lions no longer ventured onto their land. De Iongh: ‘They’re a bit like disco lights placed at different intervals along the fence that flash intermittently, which makes the lions think that the cattle are being guarded by a number of people with lanterns.’ Richard’s clever invention was so successful, other cattle farmers also installed flashing lights.


Over the past three years Lesilau has been studying whether this deterrent really does work as well as it seems. He tracks the trail of lions using a transmitter in a collar around the lion’s neck. Via a satellite connection he can see where the lions have been, whether using his smartphone while driving around the park, or at his computer in Leiden. (It’s not yet possible to do this in real time, but with a delay of three hours). Over the past three years, he has monitored 80 cattle farmers in the region, 43 of whom were using the flashing lights. His study showed that those bomas with flashing lights were hardly ever attacked. The lions travelled further away from the borders of the park and went ‘shopping’ at enclosures without the lights. Lesilau: ‘This is an important discovery. Lions are able to adapt their behaviour if the environment changes. This means they are cleverer than we thought. They do sometimes attack cattle in the bomas in daylight hours. Fewer cows or sheep fall victim because the cattle are much more spread out in the daytime.’

Doesn’t this different form of predatory behaviour mean a greater danger for humans? Not necessarily, according to the two researchers. De Iongh: ‘Obviously, lions can be very dangerous, but in this area they seldom attack people. In principle, they don’t eat humans; they prefer wild animals or livestock.’ Lesilau does advocate a better system of enclosures for the park on the city side. A few years ago a man was injured when a lion attacked him in a suburb of Nairobi. This was mainly the result of human provocation, he explained. ‘More research is needed on the long-term effects and what the consequences are if the flashing lights are installed over a wider area.’

The research is having an effect elsewhere in Kenya. Four other national parks are going to be working with Leiden researchers, examining such issues as biodiversity. As well as a Dutch PhD candidate, two new Kenyan PhD candidates have been recruited and eight Dutch and Belgian students will be taking part in the research. The Kenyan researchers will also make frequent visits to Leiden to follow courses and share knowledge. ‘It is quite remarkable that a country that doesn’t have any lions is willing to help us,’ Lesilau commented. ‘It’s really useful having scientists work together when there is a lack of knowledge in the local environment.’

This article appeared in our free alumni magazine Leidraad.

Francis Lesilau says that in one sense his career is thanks to a lion. When he was 11 he had to protect his family’s last two camels. One day, a lion suddenly appeared and bit one of the camels in the neck. For a moment, Lesilau stood helpless, eye to eye with the lion. ‘I will never forget the piercing yellow eyes of that lion.’ The lion stared at him intensely, dropped the camel and trailed off. The camel did not survive. Lesilau’s father then decided to quit keeping camels, and Francis was able to go to school. After secondary school, he studied Sustainable Management at Leicester University in England. Afterwards, he became a ranger before becoming Security Manager at Kenya Wildlife Service, where he met Hans de Iongh. This is where their collaboration started.

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