This species is found in northern Sumatra (Indonesia) in Aceh Province north of the rivers Simpangkiri and Wampu (Wilson and Wilson 1976), where the range has recently been discovered to extend to the south bank of the Simpangkiri River (Aimi and Bakar 1996). A study on the behaviour of this species was performed at Ketambe Research Station, Leuser Ecosystem, Sumatra, Indonesia (3°41 N, 97°39 E) (Sterck et al. 2005). Another study on its behaviour was performed at two sites in Leuser Ecosystem, northern Sumatra, one of which was also Ketambe, and the other was Bukit Lawang (3°30 N, 98°6 E) (Wich and de Vries 2006).