Summary
The recently discovered Callithrix humeralifer intermedius, occurs between the rios Roisevelt and Aripunã in Brazil. It is intermediate in colouration between the dark C.h. humeralifer and the pale C.h. chrysoleuca. This paper presents some preliminary observations of C.h. Intermedius in the wild from May to November 1978. They occupy dense primary forest, second growth and low white sand forest. Group size is between 4 and 13, the larger groups comprising more than one adult pair. One group, watched for 160.5 hours occupied a home range of 13.75 ha. during this period, travelling between 740 and 1500 metres during the day. Principal foods include small fruits, flowers, tree exudates and insects. Groups were observed with one pair of newborn infants during September and October, at the end of the dry season. Observations of social behaviour (including agonistic behaviour, grooming, tail coiling behaviour and scent marking), development of young, vocalizations, and potential predators are described.