Preliminary observations of the Mentawai macaque on Siberut Island,Indonesia

During 2 years spent conducting ecological fieldwork on Siberut, the largest and most northerly of the four Mentawai Islands in Indonesia, incidental observations were made of the Mentawai macaque. The Mentawai macaque has been considered variously as a full species similar in some respects to the long-tailed macaque and as a subspecies of the pig-tailed macaque. Evidence is presented that a hitherto undescribed form of the Mentawai macaque occurs on Siberut, and aspects of its ecology and behavior are described.