The genus Murina has a wide geographic distribution and includes about 35 species, but very little information is available on the maternity behaviour of any of them. We conducted a preliminary study of a maternity colony of Murina ussuriensis in warm temperate rain forest of Yakushima, Japan. Day roosts of six nursing females were located by radio-telemetry. During the eight days of the study 18 maternity roost locations were confirmed. The nine roosts that were clearly visible included four types: vertically suspended clusters of dead leaves, tree hollows, a crevice in a root plate and a completely exposed site under a branch. Whenever the same female was located on successive days, she had switched from her previous roost, and none of the roosts was re-used by a radio-tagged female during the study period. The number of individuals recorded roosting together ranged from two (a mother with infant) to 22 individuals. The first emergence of an adult female occurred between 13 and 47 minutes after sunset. Mothers returned to the roost about 30 minutes after their first emergence, repeatedly hovering near the roost, landing and departing again. Some offspring left the roost independently, while non-volant offspring were carried away by an adult, presumably the mother. Various types of social calls were recorded, beginning when the first mother returned to the roost, and then almost continuously until the last individual left the roost. These preliminary results suggest that maternity colonies show very frequent roost-switching, may exhibit fission-fusion behaviour and have an extensive vocal repertoire.