Rhesus macaques (Macaca mulatta) displaying self-injurious behavior show more sleep disruption than controls

Area of Science:

• Primate behavior
• Sleep science
• Animal welfare

Background:

• Self-injurious behavior (SIB) is a pathology seen in humans and animals, often linked to mental health conditions and sleep disruption in humans.
• In rhesus macaques, SIB involves self-biting, potentially causing wounds, with limited prior evidence of associated sleep disruption.

Purpose of the Study:

• To evaluate sleep disruption in rhesus macaques exhibiting self-injurious behavior (SIB) using a noninvasive monitoring system.
• To quantify nighttime activity patterns in SIB macaques compared to controls.

Main Methods:

• Utilized an infrared camera and video surveillance to record nighttime activity in 13 rhesus macaques (6 with SIB) over 6 nights each.
• Measured total movement time (TMT), activity in the first (HR1) and last (HR11) hours, and the number of movement videos of varying durations (≥10 secs, ≥30 secs).

Main Results:

• Monkeys with SIB exhibited significantly higher TMT (p < 0.01) and HR1 (p < 0.001) compared to controls.
• SIB macaques generated more movement videos of ≥10 secs (p < 0.01) and ≥30 secs (p < 0.01), indicating more frequent and longer awakenings.
• A four-fold increase in longer awakenings (≥30 secs) was observed in the SIB group, suggesting substantial sleep fragmentation.

Conclusions:

• Rhesus macaques with SIB demonstrate significant nighttime sleep disruption, including increased overall activity and frequent awakenings.
• The pattern of increased activity in the first hour of the night, but not the last, resembles sleep-onset insomnia observed in humans.
• The causal relationship between SIB and sleep disruption remains undetermined: whether sleep issues contribute to SIB or vice versa requires further investigation.