The Tangkoko-Duasudara nature preserve lies on the northernmost tip of the northern peninsula of Sulawesi, within the administrative province of Sulawesi Utara (North Sulawesi) at about 40km, or two hours driving from Manado.
Although named as one the Tangkoko-Duasudara nature preserve is actually two adjoining preserves. The Tangkoko Batuangus Nature Reserve (4,446ha) was established in 1919 by Dutch colonial rule under Decree No. GB 21/2/1919 stbl. 90 and was extended by the addition of the Duasudara Nature Reserve (4,299ha) in 1978 under Sk. Mentan No. 700/kpts/Um/11/78. Total land area of both preserves, including the Batuputih and Batuangus tourism areas is 8,745 ha.
The topography is dominated by the two volcanic cones of Gunung Duasudara (1,351m) and Gunung Tangkoko (1,109m), which are linked by a ridge. A further volcanic cone, the active 450m Gunung Batuangus, lies to the south-east, while to the north-west lies the extensive Pata plateau. To the north-east the steep topography attenuates towards a coast characterized by alternating bays and rocky headlands
Predominant vegetation type is primary lowland rain forest which occurs around the three main peaks and on the Pata plateau up to 600m. Above 600m, sub-mountain rain forest displays physical changes in both structure and species composition. Canopy height and mean leaf size are smaller and bryophytes and ferns predominate in the under storey and on trees.
Elevations, around the crater rim and peaks of Gunung Tangkoko and Gunung Duasudara, a stunted bryophyte and epiphyte encrusted mountain forest occurs. In areas disturbed by landslides numerous ferns are present along with pitcher plants Nepenthes sp. and some genera such as Vaccinium spp. This forest type is particularly noteworthy for orchids.
Other notable vegetation types include coastal beach forest which predominates on sandy coastal ridges and is dominated by Calophyllum soulattri and Barringtonia asiatica. A Casuarina equisetifolia dominated secondary forest occurs on newly-exposed sandy and rocky parts of the reserve, such as on the Tangkoko crater walls and floor, on the slopes of the Batuangus ash cone and on the beach close to Batuangus cone. Other vegetation types include secondary forest on the lower south-eastern slopes of Gunung Duasudara and areas of alang-alang Imperata cylindrica grassland in areas of both volcanic and anthropogenic disturbance (WWF, 1980).
The unusually high productivity of the lowland forest has resulted in a faunal composition with large numbers of relatively few species. This is exemplified by the frugivores (fruit-eaters), particularly the endemic Celebes black macaque (Macaca Nigra), for which population densities of about 300 per sq. km have been recorded, although this may have declined over recent years (MacKinnon, 1991). Other endemic species include Tarsiers (Tarsius spectrum) and Phalangers; Bear Cuscus (Phalanger Ursinus) and Celebes cuscus (P. celebensis).
Avifauna is well represented with some 140 species recorded from the reserve by 1980. Of particular interest are the Sulawesi endemic rhinoceros hornbill Rhyticeros cassidix, which occurs in extremely high numbers, and Maleo (Macrocephalon Maleo) (V), for which two main nesting areas have been identified at Rumesung and Tiwo, as well as several smaller sites at Lagunde and on the slopes of Gunung Tangkoko.
The proposed marine component of the reserve includes a variety of habitats including well-developed coral reefs. Notable species include turtles; green turtle (Chelonia mydas) (E), Leatherback (Dermochelys coriacea) (E) and Hawksbill turtle (Eretmochelys imbricata) (E), although these nest only occasionally (WWF, 1980).