How many hours do rats sleep at night? - briefly
Laboratory rats typically rest 8–10 hours during the dark phase, contributing to a total daily sleep of 12–15 hours.
How many hours do rats sleep at night? - in detail
Rats are nocturnal mammals, and their sleep during the dark phase accounts for the majority of their daily rest. Laboratory observations indicate that adult rats typically spend 8 to 10 hours sleeping while the lights are off. This nocturnal sleep is polyphasic, consisting of multiple episodes lasting from a few minutes to half an hour, interspersed with brief periods of wakefulness for foraging and grooming.
Key factors that modulate the amount of night‑time sleep include:
- Strain and genetics – Some inbred strains (e.g., Wistar, Sprague‑Dawley) show slightly longer nocturnal sleep than others.
- Age – Juvenile rats may sleep up to 12 hours during darkness, while older animals often reduce nightly sleep to around 6 hours.
- Light intensity and photoperiod – Dimmer or longer dark periods extend sleep duration; abrupt light exposure can fragment sleep bouts.
- Environmental stressors – Noise, cage enrichment, and handling increase wakefulness and shorten night‑time sleep.
- Temperature – Ambient temperatures near thermoneutrality (28–30 °C) promote longer sleep episodes, whereas cooler conditions shorten them.
Sleep architecture is typically assessed with electroencephalography (EEG) and electromyography (EMG). These recordings reveal that rats spend roughly 70 % of their dark‑phase time in non‑rapid eye movement (NREM) sleep and 30 % in rapid eye movement (REM) sleep. NREM episodes dominate the early part of the night, while REM periods become more frequent toward the end of the dark cycle.
Comparisons with wild rats suggest similar patterns, though field studies report slightly more fragmented sleep due to predator avoidance and variable food availability. Nonetheless, the core characteristic—substantial sleep concentrated during darkness—remains consistent across laboratory and natural settings.