The first weeks of cohabitation of newly-formed heterosexual pairs of common marmosets (Callithrix jacchus).

16 pairs of common marmosets were formed, six of which were observed for 7 weeks, and ten for 4 weeks. A variety of behaviours was recorded, including sexual mounting, male tongue-smacking, female slit-eyed tongue-flicking, scent marks, huddling, allogrooming and autogrooming. Behaviours associated with sexual encounters occurred initially at high levels but declined during the study period. The incidence of sexual mounting was closely related to that of male tongue-smacking and female slit-eyed tongue-flicking. Other social behaviours including scent-marking and allogrooming did not show a consistent pattern of occurrence with respect to time or sexual activity.