“…Little is known so far about marmosets, especially species of the genus Callilhrix, in their natural environment [Hubrecht, 1984a[Hubrecht, , 1985Lacher et al, 1981Lacher et al, , 1984Maier et al, 1982;Rylands, 1981;Stevenson, 1978]. The available naturalistic data are consistent with the more extensive findings on captive groups which have fo cussed primarily on the social dynamics and their underlying behavioral and endocrino logical mechanisms [Abbott, 1984;Abbott and Hearn, 1978;Epple, 1975a;Evans, 1983;Evans and Hodges, 1984;Evans and Poole, 1984;Hearn, 1983;Hubrecht, 1984b;Rothe, 1975;Sutcliffe and Poole, 1984a, b]. All these investigations have shown that in marmoset families two subgroups are of particular in terest, first the parents or the reproductive pair, often referred to as the alpha pair and secondly the mature progeny which fail to show any reproductive activity.…”