Isau-Isau Wildlife Reserve is a nature reserve in South Sumatra, Indonesia. It is home to a large number of species, many of which are threatened or endangered. Formerly protected as Isau-Isau Pasemah Nature Reserve since 1978, the modern Wildlife Reserve was founded in 2014 and is managed by the Natural Resources Conservation Agency (BKSDA) of South Sumatra Province. The reserve is listed as IUCN Management Category IV.
Geography
Isau-Isau is one of South Sumatra's largest nature reserves, at . It spans across the regions of Kabupaten Lahat and Kabupaten Muara Enim. The reserve is isolated from other protected areas due to human presence. There are 24 villages in and around the reserve, including Lawang Agung, Pagar Agung, and Tanah Abang. These villages engage in agricultural practices such as coffee and rubber plantations.
The reserve ranges between approximately 300 and 1,400 meters in elevation. Temperature and humidity vary based on elevation and forest canopy cover. In old-growth forest, temperature is lowest while humidity is highest; the opposite is true in open plantations, with intermediate conditions in secondary forest. From January to March 2022, air temperature ranged from 22.7°C to 28.3°C, while humidity ranged from 72% to 87%. Soil pH ranged from 7.2 in the forest to 7.9 on plantations.
Geology
Isau-Isau Wildlife Reserve is on a volcanic landscape in the Bukit Barisan Mountains, and peaks on Isau-Isau Volcano at 1,422-1,431m in elevation. The mountain is a mostly andesitic volcano that last erupted during the Pleistocene Epoch. Isau-Isau's eruptions released andesitic lava flows and pyroclastic flows into the lowlands. The pyroclastic flows created tuff lapilli and tuff breksi rock formations.
Hydrology
The reserve is located in the Lematang and Perapau subwatersheds, within the Musi Watershed. The rainforest mitigates soil erosion and flooding.
Ecology
Flora
Sumatran lowland rainforest covers the majority of the reserve, with some Sumatran montane rainforest at higher elevations. The core of the reserve contains old-growth forest, while secondary forest grows around villages. The forest is dominated by hardwood trees of the Dipterocarpaceae family, such as meranti (Shorea sp.). Other common trees include Pulai (genus Alstonia), durian (genus Durio), jelutong (Dyera sp.), terap (Artocarpus elasticus), white mango (Mangifera caesia), and cempedak (Artocarpus integer). Understory species include vines such as rotan (Calamus manan), shrubs such as simpur (Dilenia grandifolia) and albizia (genus Paraserianthes), and grasses like bamboo (Bambusa sp.).
The forest is home to the world's largest flower, the corpse flower (Rafflesia arnoldii), and the world's tallest flower, Amorphopallus muelleri.
At least 22 species of orchids live in Isau-Isau. 21 of these species are epiphytes (tree-dwellers) and one is terrestrial. One species in the reserve, Vanda foetida, is endemic to South Sumatra.
41 plant species in the reserve and surrounding villages are used for traditional medicine. Isau-Isau’s plants of the pepper (Piperaceae) family have antibacterial properties.
Fauna
Isau-Isau's rainforest is home to many species of primates: siamang (Symphalangus cyndactylus), southern pig-tailed macaque (Macaca nemestrina), black-crested Sumatran langur (Presbytis melalophos), Sunda slow loris (Nycticebus coucang), and agile gibbon (Hylobates agilis). Herbivores such as Sumatran porcupine (Hystrix brachyuran), lesser mouse-deer (Tragulus kanchil), sambar deer (Cervus unicolor), southern red muntjac (Muntiacus muntjak), banded pig (Sus scrofa vittatus), Sumatran serow (Capricornis sumatraensis), and Malayan tapir (Tapirus indicus) browse the flora, while the critically endangered Sunda pangolin (Manis javanica) feeds on insects. The reserve is home to the world's rarest lagomorph, the Sumatran striped rabbit (Nesolagus netscheri).
Predatory mammals of the reserve include the binturong (Arctictis binturong), Asian golden cat (Catopuma teminckii), marbled cat (Pardofelis marmorata), Asian leopard cat (Felis bengalensis), dhole (Cuon alpinus), Sunda clouded leopard (Neofelis diardii), sun bear (Helarctos malayanus), and Sumatran Tiger (Panthera tigris sumatrae).
Bats in Isau-Isau include black-capped fruit bat (Chironax melanocephalus), lesser short-nosed fruit bat (Cynopterus brachyotis), and greater short-nosed fruit bat (Cynopterus sphinx).
At least 22 bird species have been documented in the reserve. These include the white chested babbler (Trichastoma rostratum), rhinoceros hornbill (Buceros rhinoceros)and bronze-tailed peacock-pheasant (Polyplectron chalcurum).