Field data on the roosting ecology of a maternity colony of Pteropus vampyrus natunae in a peat swamp forest in Sarawak were collected for 19 mo. The colony moved between 10 roost sites and the diurnal home range (comprising only day-roost sites) was about 1120 ha. Two movement phases were observed within the diurnal home range. The first phase consisted of continuous movement between roost sites each month (August 1998 to January 1999, and August to November 1999), and this coincided with the months in which late pregnancies and pups dependent on mothers were seen. The second phase had almost zero or restricted movement each month (February to July 1999, and December 1999 to March 2000). Throughout the diurnal home range, the colony roosted in 20 families of trees (27 genera and 31 species). The bats tended to roost in certain species and sizes of trees.