Grooming circadian rhythmicity, progesterone levels and partner preferenceof the reproductive pair of a captive common marmoset (Callithrix jacchus)family group during pregnancy and after parturition

One family group of common marmosets (Callithrix jacchus) maintained in cap tivity under natural environmental conditions (Natal, Brazil, 05 degrees 46 'S, 35 degrees 12'W) was observed by focal sampling at two non-consecutive days per week during two nonconsecutive pregnancies (pregnancy 1: the last 8 fortnights before parturition; pregnancy 2: the last 5 ones) and after pa rturition (4 fortnights for both). The hourly percentiles of the duration o f self-grooming and allogrooming interactions of the reproductive pair were submitted to Cosinor analysis for the 24-h period (p less than or equal to 0.05). The reproductive female's progesterone was monitored by fecal colle ction twice a week between 7: 00 h to 9: 00 h. Levels of progesterone were determined by ELISA method. During pregnancy 1, all interactions of the rep roductive pair showed a 24-h statistically significant period. However, aft er parturition this periodicity is not present in some behaviors of the rep roductive male. This animal presents the 24-h periodicity only toward to th e reproductive female, the subadult son and to the newborns. Hormonal level s of the reproductive female showed isolated increases above 100 ng/g at th e second and third fortnight after parturition, but did not characterize ov ulation. Between pregnancy 1 and 2, the family was increased by the birth o f four animals. During pregnancy 2, a statistically significant 24-h period was find only in self-grooming of the reproductive male and female, and in the interactions between the reproductive pair. Also, in the interactions of the reproductive male with only one of the juvenile son. After parturiti on the reproductive female ovulated at the second fortnight and became preg nant again. At this time, those interactions still have a 24-h period, exce pt in grooming directed to the juvenile son by the reproductive male. As in the first post-partum, grooming directed to the newborns showed statistica lly significant 24-h period. These results suggest that the reproductive pa ir performs 24-h rhythmic grooming interactions only with some animals, sup posed to be the preferential grooming partners. Furthermore, the temporal g rooming expression in common marmosets may be affected by the reproductive condition (progesterone levels) of the reproductive female, by the care of newborn after parturition and the group size.