Animals tend to divide their days into longish periods of different predominant maintenance activities, such that, for instance, early morning and late afternoon feeding periods are clearly separated by a midday rest period. Frequencies of social behaviour are known to change with change in the predominant activity. As an obvious example, grooming tends to be more frequent during rest periods than when the animals are moving and feeding. However, the possibility that patterns, as opposed to frequencies, of social interaction could change through the day has rarely been mentioned, let alone considered in detail. Data from a two-year field study of wild mountain gorilla, show that patterns of social interaction do indeed change with the predominant maintenance activity : neglect of such variation can lead to, at best, ignorance of interesting facets of behaviour and, at worst, misleading conclusions about the social relationships of the study animals.