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Researchers affiliated with the University of Nottingham observed at the beginning of February that Southeast Asian rainforests can be food deserts for wildlife, though the Chewong are making a difference for terrestrial mammals. The reason, the scholars reported in a journal article, is that the forests do not produce an abundance of fruits. The investigation has significant implications for the conservation of rainforests.

A dipterocarp forest in the Sabah state of Malaysia

A dipterocarp forest in the Sabah state of Malaysia (Photo by Col Ford and Natasha de Vere on Flickr, Creative Commons license)

The study reported that the famed dipterocarp forests, dominated by giant, emergent trees, typically produce mast crops only irregularly, at intervals of perhaps two to seven years. As a result, frugivorous animals occur in relatively low densities in these forests since they are sensitive to the irregularity of the mast crops. The researchers investigated the role of the Chewong fruit gardens in possibly benefiting forest wildlife.

The researchers did their study in the Krau Wildlife Reserve, a 600 square km. tract of forest land located roughly in the center of Peninsular Malaysia. It has been continuously occupied by the Chewong, at least since the reserve was gazetted in 1923.

About half of the 400 or so Chewong continue to live within the reserve boundaries. They still practice traditional cultivation methods plus they subsist on fish, hunted game, herbs and the wild fruits they gather—the subject of the research project. They clear patches of forest for planted crops next to some of the fruit gardens they have established within the forest. The Chewong are limited in the extent of their integration into the larger Malay society and they are highly reliant on forest products for their livelihoods.

Chewong techniques for developing and managing their fruit gardens include selecting suitable tracts of forest lands, removing some trees either for building materials or just because they are not wanted, then planting desirable fruiting native trees such as mango, durian, kepayang, cempedak, and rambutan. The fruit gardens are tended a little, and the fruit is collected every year from June through August for as long as 50 years.

A durian tree covered with fruit

A durian tree covered with fruit (Photo by Zaqqy on Flickr, Creative Commons license)

The fruit gardens are developed in patches that are contiguous with the original forests, with very little clearance of the old growth. Much of the original vegetation is left intact. The net result is that the original forest is maintained, only it is augmented with higher densities of seasonally available fruit crops.

The goal of the project was to ascertain in what ways the Chewong fruit gardens influence the composition, abundance, and diversity of terrestrial mammals. The procedure of the scientists was to use camera traps to survey animals moving along game trails in the fruit gardens and, as controls, along similar game trails in nearby forests that were not and had never been fruit gardens.

The authors relied on Chewong guides to identify areas that are, or had been, fruit gardens in the forest versus the control plots on natural, unmodified forestlands. The researchers established seven study plots in the fruit gardens and eight plots in the control areas. They studied the images of the animals the cameras recorded at each plot for eight weeks.

A Malayan tapir in the Taman Negara National Park of Malaysia

A Malayan tapir in the Taman Negara National Park of Malaysia (Photo by Bernard Dupont on Flickr, Creative Commons license)

The camera traps recorded 1678 individual animals, including 16 species of mammals, four species of birds, and one reptile species. Nine of the species have IUCN protected status, including the Malayan tapir, an endangered species. Four of the tapirs were detected in the fruit gardens though, significantly, none in the control plots.

Of the six species of mammals that the IUCN lists as “vulnerable,” five of the Asian small-clawed otters appeared in the fruit gardens but none were recorded in the control areas. All of the species they recorded were found within the fruit gardens but only 16 also occurred in the control plots.

The results showed that the higher density of fruiting trees in the fruit gardens supported a greater diversity and biomass of terrestrial, frugivorous mammals compared to the control plots. This clearly demonstrated “that fruit gardens are playing an important role in attracting and supporting terrestrial mammals (p.136).”

The reason is simple: the fruit gardens contain a greater number of tree species that produce fleshy fruits. But there are serious implications, such as the possibility of enhancing mammal habitat by improving the availability of fruiting forest trees, a management strategy that may have widespread potential for other tropical regions.

The authors emphasized several factors that enhance the fruit gardens as places that wildlife favor. One is that the Chewong locate their fruit gardens right within the intact forest ecosystems in the Krau Wildlife Reserve, instead of on the periphery of the forests as many other indigenous, forest-based people do.

Another crucial factor is that the Chewong fruit gardens have the same basal areas as the surrounding forests. They have limited scale and have been developed by the Chewong with only limited clearance of native trees. The Chewong typically maintain the original structure of the canopy and the natural composition of the vegetation. Other agroforestry plots reported in the literature have been managed more intensively, which has resulted in fewer mammals, especially arboreal species that are disrupted by reductions of the canopy.

A long-tailed macaque eating a rambutan fruit

A long-tailed macaque eating a rambutan fruit (Photo by Elizabeth Donoghue on Flickr, Creative Commons license)

The researchers found an abundance of small mammals along the forest floor, such as the long-tailed macaques, which were recorded primarily in the fruit gardens. They evidently thrive on fruits such as the rambutan produced by trees that the Chewong have planted.

But that leads to another point. The abundance of small mammals suggested a “partially defaunated system,” the authors observed. Large-bodied mammals, such as elephants and rhinos, which normally would also be eating the fruits, were not recorded because they have been eliminated from that part of Malaysia. Those animals would disperse seeds better and farther than the smaller mammals. Hence, the Chewong, through the creation and maintenance of their fruit gardens, are partially replacing the large mammals in that ecological seed dispersal service.

A news release quoted Dr. Markus Eichhorn, a forest ecologist in the School of Life Sciences at the University of Nottingham and one of the co-authors of the study as saying, “In this wildlife reserve we have found that the traditional practices of the local indigenous people can have some benefits for animal conservation.”

In a different news story last Thursday, Colin Nicholas from the Centre for Orang Asli Concerns was quoted as agreeing—the investigation has important implications for the Chewong. Proposals to resettle them out of the Krau Reserve should be reconsidered. The people who live in the forest still practice a traditional way of life, and this research provides “a very strong argument for not removing them,” he argued.

Moore, Jonathan Harry, Saifon Sittimongkol, Ahimsa Campos-Arceiz, Tok Sumpah, Markus Peter Eichhorn. 2016. “Fruit Gardens Enhance Mammal Diversity and Biomass in a Southeast Asian Rainforest.” Biological Conservation 194 (February): 132–138