I'm doing some sleep research and would like to compare a human sleep pattern as recorded by a wrist-based actigraph with a "natural" sleep pattern, such as from apes. In an experiment like that, a human wears an activity monitor on a non-dominant arm over multiple days. The monitor analyzes activity pattern and can detect when the user is asleep versus active.
Can someone suggest a research article or a website that did a sleep study of primates (monkeys/apes) either in captivity or natural habitat over multiple days?
I'm particularly interested in how consistent their bedtimes are - do primates go to sleep in the evening whenever they feel like, or do they stick to a more consistent sleep schedule?