Effects of separation and novelty on distress vocalizations and cortisol in the common marmoset (Callithrix jacchus)

In socially-bonding species, separation from familiar attachment figures is widely known to stimulate a physiological. and behavioral stress response. This study investigated the hormonal and vocal responses of adult common m armosets to separation from familiar group members and to 24 hr of cohabita tion with an unfamiliar opposite-sex conspecific, All subjects were removed from their home cages and placed into a novel environment for 20 min. In o ne group, marmosets were exposed to an unfamiliar, opposite-sex partner in the novel environment and remained paired with this partner for the 24 hr t est period. In three other groups, marmosets experienced the novel environm ent alone and subsequently were returned to their original social- or singl e-housing condition, or kept separate from their social groups for a 24 h p eriod. Blood samples were collected the day before, and at 30 min, 90 min, and at 24 h after separation. Cortisol responses were differentially affect ed by the length of separation and the presence of unfamiliar conspecifics. Brief separation followed by the return to the social group had minimal ef fect on plasma cortisol levels. All marmosets produced high levels of separ ation calls in the novel environment, but there was no apparent relationshi p between calling and cortisol levels. The lack of a temporal relationship between the production of distress vocalizations and serum cortisol has pre viously been noted in squirrel monkey and rhesus monkey infant separation s tudies; the behavioral and physiological responses to;separation appear to be similarly dissociated in the marmoset, Further, the characteristics of a separation environment can differentially affect the hormonal response by adult marmosets without differentially affecting their behavioral response. Am. J. Primatol. 47:209-222, 1999. Published 1999 Wiley-Liss, Inc.(dagger)