Fecal steroids of breeding and non-breeding free-ranging black-tufted marmoset females.

The relationships between members of the groups include behaviors related to affiliation, dispute for dominant positions, parental care, and facing disputes for food and territory. All these activities are under hormone modulation and those of a steroidal nature are heavily involved. Despite this, only few data are available on steroid hormones in free-ranging marmosets of the Callithrix genus, which limits the understanding of the physiological functioning and modulation of the socio-sexual behavior by steroid hormones of this taxon. In this study, we characterized fecal concentrations of progesterone, estrogens, and glucocorticoids of six breeding and non-breeding females from two groups of free-ranging Callithrix penicillata (É. Geoffroy, 1812). The concentration of progesterone was significantly higher in females which gave birth, compared to non-breeding females. The levels of fecal estrogens and glucocorticoids did not differ between breeding and non-breeding females. The data are in agreement with the few studies on steroid values of wild and captive marmosets. This study shows the concentrations of progesterone and glucocorticoids in free-ranging C. penicillata for the first time, and it is the only study reporting the concentration of fecal estrogens in wild marmosets. Overall, the high levels of progesterone associated with pregnancy in free-ranging C. penicillata as well as levels of estrogens and glucocorticoids close to those reported for other species, suggest a conserved pattern of hormonal secretion between Callithrix species that have been studied in captivity.