By Erin P. Riley, 19th May 2023
I’ve been visiting the Indonesian island of Sulawesi for over 20 years to study its primates, so this wondrous island’s mountainous landscapes and twisty-turny roads are familiar terrain. The massive limestone formations—known as tower karsts—that stretch across a portion of Sulawesi’s southern peninsula were new to my eyes though. Rising up hundreds of meters, with jagged edges dotted with vegetation and an abundance of hidden caves and crevices, these spectacular tower karsts encompass a portion of the protected area known as Bantimurung Bulusaraung National Park, an approximately 43,000 ha area designated to protect the vegetation and wildlife that call these karst forests their home.
I first began working in this area in 2010, when I learned that groups of an Endangered primate found only on Sulawesi—the moor macaque Macaca maura—were habituated to people and hence could be easily observed here. During my summer research trips to the Park, I would stay in the nearby village of Bengo, living with villagers. My hosts would often say to me, ‘why travel all the way to the National Park (which is actually only 7 km away), when you can study the monkeys in our backyard?’. Their so-called backyard comprises a mixture of agricultural land and heavily modified forest (known as the Education Forest) that is managed by the Faculty of Forestry at Hasanuddin University in the provincial capital of Makassar. This land, which was originally forested, has experienced a long history of anthropogenic modification, primarily forest clearing for shifting cultivation. In the late 1960s and early 1970s, the Indonesian government initiated restoration efforts that involved the planting of non-native tree species such as Sumatran pine, acacia, and Honduran mahogany. There are also patches of young secondary forest in this mosaic landscape, and in the patches that border settlements, villagers have planted candlenut, wild mangoes, jackfruit, ebony and sugar palm.
Primates living in mosaic landscapes like these is an increasingly common reality in Indonesia as well worldwide. Because the groups living in the Education Forest were not habituated to observers, we began studying their use of the habitat, and in particular the frequency and timing of their feeding on agricultural crops grown in and along the border of the forest, using camera traps, enabling us to observe their behaviour remotely. To complement the camera-trap data, we also conducted interviews with local villagers and farmers to assess their knowledge of and attitudes towards the monkeys and their crop feeding behaviour. Understanding flexible foraging behaviour, such as crop feeding, also requires knowing what’s happening in the surrounding forest in terms of food availability. We therefore set up vegetation plots to assess what food trees were available in this heavily-modified forest. Given that moor macaques are primarily frugivorous, we collected fruit samples to assess their nutritional value. Because our colleagues from Roma Tre University in Italy had collected similar data from the karst forest in the well-protected Bantimurung Bulusaraung National Park, we had an excellent opportunity to compare the habitat quality of two forests known to be home to moor macaques.
Primary forests are generally considered the most important for species conservation, but could heavily-modified forest such as the Education Forest also have conservation value? Our research generated some unexpected findings. Our initial assumption was that the protected karst forest would be better quality habitat for the macaques. We were correct, but only partially! Although the protected karst forest had a greater number of and more diverse macaque food trees, we found that estimates of food productivity were greater in the heavily modified Education Forest.
We also found that that the two forests shared elements that make happy macaques! For example, the family Moraceae, which comprises figs and other species known to be important food resources for a wide array of wildlife, including moor macaques, was the most dominant family in both the protected karst forest and the Education Forest. In addition, the fruits we were able to collect from each of the forests showed a similar balance of critical macronutrients, that is, fats, carbohydrates, fibre and protein.
Our research findings are important because they further support the argument that heavily-modified forests, such as the Education Forest, should not be overlooked for the habitat they provide and the role they can play in wildlife conservation. Importantly, our findings do not mean we should no longer care about preserving primary forests. Rather, in addition to protecting remaining primary forests, we should also assess the potential conservation value of heavily modified habitats and prioritize ways to further increase their value, such as planting trees known to provide food and shelter for resident wildlife.
The article “The potential conservation value of anthropogenically modified habitat for the Endangered moor macaque Macaca maura in Sulawesi, Indonesia” is available in Oryx—The International Journal of Conservation.