SOCIAL AND REPRODUCTIVE CONDITIONS MODULATE URINARY CORTISOL EXCRETION IN BLACK TUFTED-EAR MARMOSETS (CALLITHRIX KUHLI)

The links between psychosocial stress, social status, reproductive fun ction, and urinary cortisol were assessed in social groups of black tu fted-ear marmosets (Callithrix kuhli). Urinary cortisol excretion was monitored in cases of intrafamily conflict (''sibling fights'') and in daughters in four distinct social contexts: in the family group, whil e housed singly or in same-sex pairs, and while paired with a male pai rmate. Cortisol excretion was elevated in participants in intra-family conflict on the day of and the day following the conflict, relative t o concentrations a week prior to or following the conflict, Daughters in natal family groups had concentrations of cortisol that did not dif fer from reproductively active adult females. This finding held for da ughters who were either anovulatory or undergoing ovulatory cycles whi le in the natal family group. Natal family members and male pairmates exerted buffering effects on levels of activity in the hypothalamic pi tuitary adrenal axis (HPA) in female C. kuhli. Placing females in soli tary housing led to significantly increased cortisol excretion, In the 2 months subsequent to pairing with a male partner, excreted cortisol concentrations in females declined significantly. Daughters removed f rom their natal family group and housed with a sister did not exhibit increased cortisol levels. These data reveal that activity in the (HPA ) axis in marmosets is sensitive to psychosocial stressors, and that u rinary cortisol can provide a useful quantitative measure of HPA react ivity, As in other callitrichids, delayed breeding in daughters and re productive anomalies in C. kuhli appear to be mediated by mechanisms o ther than elevated HPA activity. (C) 1997 Wiley-Liss, Inc.