When do mice sleep? - briefly
Mice are primarily nocturnal, resting during daylight and typically obtaining 12–14 hours of sleep each day. Their rest is fragmented into several short bouts rather than a single continuous period.
When do mice sleep? - in detail
Mice are primarily nocturnal mammals; the bulk of their rest occurs during the dark phase of the light‑dark cycle. In a typical laboratory setting with a 12‑hour light and 12‑hour dark schedule, they begin to settle down shortly after lights turn off and remain inactive for most of the night.
Total daily sleep averages 12–14 hours, divided into multiple short bouts rather than a single long episode. A single sleep episode usually lasts 5–30 minutes, and a mouse may experience 10–20 such periods each day.
The sleep architecture comprises two main stages:
- Non‑rapid eye movement (NREM) sleep – accounts for roughly 80 % of total sleep time; characterized by low muscle tone and slow brain waves.
- Rapid eye movement (REM) sleep – makes up the remaining 20 %; associated with dreaming‑like brain activity and muscle atonia.
Both stages appear cyclically throughout the night, with REM episodes typically shorter and more frequent toward the end of the sleep period.
Factors influencing the timing and duration of rest include:
- Light exposure – darkness triggers the onset of sleep; sudden illumination can interrupt ongoing bouts.
- Ambient temperature – optimal range (20–24 °C) promotes stable sleep; extreme temperatures shorten sleep periods.
- Age – juvenile mice display longer total sleep and more fragmented patterns; older individuals may show reduced REM proportion.
- Strain differences – some genetic lines exhibit altered circadian phase or increased total sleep compared with standard laboratory strains.
- Feeding schedule – restricted or timed feeding can shift the onset of sleep to align with periods of food scarcity.
In natural habitats, mice retain the nocturnal pattern but may adjust activity to avoid predators, leading to occasional daytime naps when shelter provides safety.
Overall, mouse sleep is polyphasic, dominated by the night, and modulated by environmental cues, physiological state, and genetic background.