Rank orders of arising,eating, and retiring in a family group of tamarins (Saguinus fuscicollis)

A family group of tenS. fuscicollis, housed in a greenhouse and subjected to natural variations in day length, was observed for a period of three months. All animals ordinarily slept together in the same hutch box. The order in which the various animals emerged in the morning was almost the precise inverse of the order in which they retired at night. Each of these orders was quite reliable and was related in nonlinear fashion to age—the ranks of the youngest offspring being the closest to those of the parents. Time of emergence and eating in the morning consistently preceded sunrise by about 30 min and was initiated by the oldest offspring; retiring was much more variable and was led by the parents.