Circadian rhythmicity of grooming behavior during pregnancy in a marmoset (Callithrix jacchus) family group in captivity

One family group of common marmoset (Callithrix jacchus) was observed in ca ptivity under natural environmental conditions to describe the circadian pa ttern of grooming behavior during the pregnancy of the reproductive female. The animals were observed by focal sampling, from the beginning to the end of animal's active phase, during two non-consecutive days per week, from A ugust to November 1996. The duration of self-grooming and social grooming b ehavior of each animal were totalled each hour. The time series obtained we re analyzed by Cluster Analysis and by Single Cosinor Analysis. The daily p atterns of grooming behavior during pregnancy were divided by Cluster Analy sis into two stages, one corresponding to the second half of the third mont h of pregnancy, and the other from the last half of the third month to the last week before parturition. The confidence intervals of acrophases overla pped in all stages. The acrophases values of the first stage occurred betwe en 10:09 h and 11:00 h, and on the second stage between 8:51 h and 11:13 h. The daily pattern of grooming behavior of adult male and female showed a t rend to increase in the first hours of the active phase. This trend to adva nce grooming behavior during the second stage of pregnancy may be due to an effect of the coming parturition itself or to seasonal influences.