Do primates other than humans have a consistent sleep schedule?

Question

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?

Answer 1

This is only a partial answer, but a reasonable starting point.

In a blog-article "The Evolution of Primate Sleep", the author identified 3 main patterns - the third pattern seems most relevant to your question.

What he found was that there are 2 divisions of sleep patterns - several primates, such as some species of lemurs are nocturnally active, whereas apes, gorillas etc tend not to be active at night. Seemingly adapting to the diurnal cycle. In the article "Mammalian Sleep Dynamics: How Diverse Features Arise from a Common Physiological Framework " (Phillips et al.), primates uniquely undergo monophasic sleep.

Answer 2

Check out Sleep Architecture in Unrestrained Rhesus Monkeys (Macaca mulatta) Synchronized to 24-Hour Light-Dark Cycles. From the abstract: "With minor exceptions, most notably a delay in peak delta activity, sleep-wake architecture, regulation, and consolidation in rhesus monkeys strongly resembles that of humans."