The siamang (Siamanga syndactyla) is a great ape peculiar to the island.
In point of doctrine, they differ in their view of the relation between God Vishnu and the human soul; whilst the former sect define it by the ape theory, which makes the soul cling to God as the young ape does to its mother, the latter explain it by the cat theory, by which Vishnu himself seizes and rescues the souls as the mother cat does her young ones.
Bachian is remarkable as the most eastern point on the globe inhabited by any of the Quadrumana, a black ape occurring here as in Celebes.
The celebrated ape "Mafuka," which lived in the Dresden zoological gardens during 1875, and came from Loango, was apparently a member of this species, although it was at one time regarded as a hybrid between a chimpanzee and a gorilla.
Mammals are few in species, but remarkable, especially Macacus niger, an ape found nowhere else but in Bachian; Anoa depressicornis, a small ox-like quadruped which inhabits the mountainous districts; and the babirusa or pig-deer of the Malays.