Behavioral sleep in captive owl monkey (Aotus azarae) and squirrel monkey (Saimiri boliviensis).

The objective of this study was to test the hypothesis that activity-behavioral sleep parameters differ between nocturnallyactive owl monkeys and diurnally-active squirrel monkeys which are sympatric and of Bolivian origin. The total sleep time (TST) and sleep episode length (SEL) of 7 adult owl monkey siblings and 4 adult squirrel monkeys were quantitated by actigraphy for 7 days under captive conditions. The higher TST/24 h values and longer SEL/12 h quiescent phase quantitated for owl monkeys in comparison to that of squirrel monkeys clearly indicate that the behavioral sleep is markedly different between these two groups, though they are sympatric in wild. Significant differences noted in the sleep architecture between squirrel monkeys and owl monkeys can be attributed to the influences in the selected sleep niche, threat perception from predators, and disturbances from natural elements (especially rain) in the natural habitat.