Social and developmental influences on urinary androgen levels in young male white-faced marmosets (Callithrix geoffroyi)

Abstract

Callitrichine primates (marmosets and tamarins) often remain in their natal groups beyond the time of sexual maturity. Although studies have characterized the development of female reproductive function in callitrichine offspring, less is known about the male reproductive development. To document reproductive development in male marmosets, we monitored urinary androgen (uA) excretion in males housed in a captive colony of white-faced marmosets (Callithrix geoffroyi). Young male marmosets showed relatively low and stable rates of uA excretion early in life, with elevated production at the end of the juvenile period (9-10 months) and again at the onset of adulthood (16 months). uA levels of adult breeding males were also measured to compare to adult-aged sons. Although breeding males did have higher uA levels than their adult-aged sons, these differences did not reach conventional levels of significance. Evidence from some other reports has suggested that androgen levels of males in other species are influenced by social factors, such as the presence of a sexually receptive female or of dependent offspring. In this study, however, uA levels did not vary, based on their mothers' pregnancy status or the presence of younger siblings in the natal group. Patterns of androgen excretion in the white-faced marmoset roughly reflect those of other callitrichine species. Furthermore, unlike callitrichine daughters, gonadal activity in sons does not seem to be sensitive to within-group social cues.

Fig. 1

Patterns of monthly mean urinary androgen (uA) (μg/mg Creatinine) ± SEM across developmental life stages of young white-faced male marmosets with a comparison of average uA levels for breeding males. Mean uA levels for each life stage were significantly higher than the previous life stage, with the exception of juvenile stage uA levels, which were higher than infant uA levels, though not significantly. Fathers showed higher uA levels than young adult males still living in their natal groups, though the difference was not significant. Life stages adapted from Yamamoto [1993]. *P < 0.05, ^†P = 0.07; n.s., not significant.

Fig. 2

Urinary androgen (uA) levels of fathers and sons 30 days before parturition and 30 days following parturition. Sons’ average uA levels did rise following the birth of infants, though not significantly.