DEVELOPMENT OF HETEROSEXUAL RELATIONSHIPS IN WIEDS BLACK TUFTED-EAR MARMOSETS (CALLITHRIX KUHLI)

In tamarins and marmosets, long-term stable sociosexual relationships are formed between heterosexual adults, but these ''monogamous'' relat ionships are often formed in groups that contain multiple adults of bo th sexes. The patterning of interactions during pair formation may the refore be shaped by this demographic profile. We evaluated the develop ment of sociosexual relationships in six captive pairs of Wied's black tufted-ear marmosets (Callithrix kuhli) during the 80 days from the i nitial day of pairing. Social behavior, sexual behavior and activity p rofiles were recorded. Social behaviors, including allogrooming, groom ing solicitation, and intragroup monitoring calls, increased across th e four 20-day time blocks. Males were more responsible than females fo r maintaining intrapair proximity during the first 40 days of pairing. Females and males were equally responsible for intrapair proximity ma intenance after this time. The highest rates of sexual behavior, inclu ding copulation and preceptive open mouth displays, occurred upon pair ing and then decreased non-significantly over time. The results indica te that sexual relationships in callitrichid primates are not dependen t on the prior existence of a social relationship between males and fe males. Higher rates of copulation, greater male responsibility for pro ximity maintenance, and male initiative in sexual interactions early i n pairing are consistent with a male reproductive strategy in which ma le-male competition may be common. (C) 1995 Wiley-Liss, Inc.