By Cathy Watson

At 8 a.m. on New Year’s Day, Ezekiel Okenye is watching a group of colobus monkeys. “I have seen them eating the leaves of 18 different tree species,” said the 25-year-old who is collecting data on the weaning of colobus babies. “At two months, they start to play with leaves.”

Kenya’s coastal colobus is the nationally threatened Angolan black and white colobus, sub-species Colobus angolensis palliatus.

Classified as Vulnerable, it belongs to one of 37 species of leaf-eating monkeys in the world that have a “sacculated stomach” where leaves are digested by bacterial fermentation.
Khalfani Mwitu is equally hard at work on the first day of 2023. “At Colobus Conservation, we have had some success.

On the coast south of Mombasa, the colobus population is stable at about 380 individuals. Colobus monkeys are forest indicators. There is enough food,” said the longstanding staff member, who runs the NGO’s tree planting, education and fieldwork.

Started in 1997, Colobus Conservation is famous for its canopy bridges across roads in Diani, a 12 km stretch dotted with beachside resorts, hotels and villas. Vehicles still kill about three monkeys a month. But the bridges enabled roughly 250,000 safe crossings in 2022, improving survival not just of colobus as well as of yellow baboons, Sykes, Vervets and greater and lesser Galagos.

A prime example of a conservation group focused on a charismatic mammal but with a far wider impact, Colobus Conservation is encouraging the growth of native coastal forest trees rather than exotic Neem and Casuarina trees, which are far less friendly to biodiversity. “I have never seen Colobus eat Neem leaves,” said Mwitu.

“The need for our work has intensified over the years due to increased development,” said manager Susan Maingi. “So, we have broadened to focus on habitat conservation, community linkages, people/primate conflict management, welfare, education and eco-tourism.”

“Coastal forests are vital water catchments for rivers and streams on which people and tourism depend,” said Paul Matiku, Executive Director of Nature Kenya. “They are also centres of endemism for globally threatened flora and fauna and provide products of great economic benefit such as honey.”

Slow and very poor in terrestrial movement, colobus monkeys rarely descend to the ground and need tree connectivity. But “forest” does not have to be something that stands apart on separate land. It can also be trees around schools, shops, hotels, homes and along roadsides, and that is Colobus Conservation’s approach — increase native tree cover wherever trees can be grown.

In the leafy shady compound of the Colobus Conversation headquarters, Mwitu stands proudly in his nursery which in 2023-2025 will raise 6,000 trees of 45 native species.
“Hotels buy our seedlings or give us money so we can plant,” said the 40-year-old from the coastal Digo community. “We have done training for their gardeners. There are those that call and say ‘Come and see the progress of the trees.’”

He has rallied 12 local nurseries too. “We have a Diani Indigenous Tree Growers Association,” said Mwitu. “When customers come, they can say ‘buy this one, but also buy this indigenous one too’.”

It is not all plain sailing, however. “Some hotels say ‘we will get back to you’,” Mwitu added, “but they never get back. And at schools, we can have a teacher who is so interested in conservation then he is moved to another school.”

With a diet almost exclusively of tree leaves and sometimes young fruits and pods, what trees do colobus need? Mwitu and Okenye said there are three favourites: Markhamia zanzibarica, the cousin of Markhamia lutea, the tall yellow flowering tree common at higher altitudes in East Africa. M zanzibarica is shorter, straggling, has russet-coloured flowers and is used for poles, firewood, bows and arrows and tool handles; Adansonia digitata or baobab, the legendary water- storing tree, which has leaves so delicious that in many countries where baobabs grow, they are eaten as a sauce; Hunteria zeylanica, an evergreen tree up to 15 m. “They like this one so much,” said Mwitu.

Peter Fundi, East Africa’s leading colobus expert, says that the coastal colobus eats the leaves of at least another 24 plant species: Balanites maughamii, Carpodiptera africana, Combretum schumannii, Cordia goetzei, Croton megalocarpus, Cussonia zimmermannii, Diospyros squarrosa, Euphorbia nyikae, Fernandoa magnifica; Ficus bubu, F lingua, F polita and F sycamorus, Grewia plagiophylla and G vaughanii, and Lannea schweinfurthii and L welwitschii; Lecaniodiscus fraxinifolius, Millettia usaramensis, Oncoba spinosa, Pycnocoma littoralis, Sideroxylon inerme, Trichilia emetica, and Zanthoxylum chalybeum.

Fernandoa magnifica, a tree favoured by the colobus and could be trialed as a street plant in Mombasa.

Asked about the future of colobus in this coastal strip, Fundi, who is affiliated with the Institute of Primate Research, said: “If we can maintain the present state of the habitat and not have major development (project), the population is a little bit safe. All that colobus monkeys need is enough healthy leaves, and they can thrive around hotels, homes, schools and even hospitals”.

Then, rather surprisingly, Fundi said some will need to be moved because of “local extinction risk”. “We need to assist in the dispersal of a few family groups to the North Coast” – to places such as Arabuko Sokoke Forest and areas around Kilifi.

Fundi was responsible for the highly successful translocation of 142 colobus monkeys in 22 family groups from denuded land on the Aberdares to Nairobi’s Karura Forest near Nairobi between 2014 and 2016. They now number 211.

Visitors to Diani need to go out of their way to visit Colobus Conservation. Also, just as importantly, in whatever hotel they stay, they need to ask the manager if he or she is planting the right trees for colobus monkeys.

“We need everyone on board,” said Mwitu. “Conservation is not a one-person show.”

Elsewhere in Kenya, a larger population of Colobus angolenses lives within the protected area of the Shimba Hills in Kwale County. The Tana River Red colobus is found in the Tanagallery forest; Colobus guereza kikuyensis and Colobus quereza matschei in Kenya’s highlands and Mau escarpment; and Colobus quereza percivial in the Matthews Range in Laikipia County.

Learn more at

Cathy Watson is Chief of Partnerships at the Center for International Forestry Research CIFOR-World Agroforestry (ICRAF).