The host-associated microbiome affects individual health and behaviour, and may be influenced by local environmental conditions. However, little is known about microbiomes' temporal dynamics in free-living species compared with their dynamics in humans and model organisms, especially in body sites other than the gut. Here, we investigate longitudinal changes in the fur microbiome of captive and free-living Egyptian fruit bats. We find that, in contrast to patterns described in humans and other mammals, the prominent dynamics is of change over time at the level of the colony as a whole. On average, a pair of fur microbiome samples from different individuals in the same colony collected on the same date are more similar to one another than a pair of samples from the same individual collected at different time points. This pattern suggests that the whole colony may be the appropriate biological unit for understanding some of the roles of the host microbiome in social bats' ecology and evolution. This pattern of synchronized colony changes over time is also reflected in the profile of volatile compounds in the bats' fur, but differs from the more individualized pattern found in the bats' gut microbiome.