Sleep quantitation in common marmoset, cotton top tamarin and squirrel monkey by non-invasive actigraphy

Sleep quantitation data on the Neotropical primate species, apart from the squirrel monkey, are still sparse. As such, we have quantitated sleep in the common marmosets (Callithrix jacchus), cotton top tamarins (Saguinus oedipus) and squirrel monkeys (Saimiri sciureus) reared in one primate facility simultaneously, by non-invasive actigraphy. The range in total sleep time/24 h measured for male adult common marmosets, cotton top tamarins and squirrel monkeys were 713–793 min (n = 4), 707–889 min (n = 4) and 459–475 min (n = 2) respectively. The range in sleep episode length /12 h dark phase for marmosets, tamarins and squirrel monkeys were 21–52 min (n = 3), 10–28 min (n = 4) and 9–15 min (n = 2) respectively. Since vigilance is a critical evolutionary adaptive feature of predator avoidance among Callitrichid monkeys and squirrel monkeys, the shorter ranges in sleep episode length recorded, even under captivity, in this study could be interpreted as probable indicators of such vigilance behavior during the rest phase. We hypothesize that the vigilance behavior when it exists during a primate's active phase should also prevail when it is at rest (sleep). This hypothesis deserves additional testing in female Callitrichid monkeys.