Behavioral and physiological response of juvenile sooty mangabeys to reunion with their mothers following a year's absence.

The return of 6 juvenile mangabey monkeys to their social group following an absence of a year resulted in increased basal cortisol secretion for both the offspring and the mothers and in significant decrements in the absolute number of lymphocyte subsets for the offspring. Six 9-month-old sooty mangabeys were removed from their socially housed mothers, subsequently peer housed, and returned to the maternal social group 1 year later. Offspring showed a significant increase in cortisol levels 24 hr following reunion (48 +/- 6%) and this difference persisted through 1 month, while the mothers showed a significant increase only at the 24-hr sample point (18 +/- 3%). Moreover, the offspring, but not the mothers, showed a significant decrease in lymphocyte subsets which were evident through the 1-month sample point. Behavioral data revealed a significant positive correlation between the percent of total scan samples offspring were with their mothers (proximity, contact, huddle) the day of return and the offspring's percent change from baseline in total T cells 24 hr later, r = 0.84. All mother-offspring pairs with the exception of one exhibited frequent affiliative behaviors toward one another by 6 days following the return. These data demonstrate that the reunion of juvenile mangabeys with their mothers after a year's absence is an acute stressor for the mothers and a relatively longer term stressor for the offspring, and that behavioral interactions which characterize the return of individual subjects to the natal group can predict acute physiological responses.