When do rats sleep? - briefly
Rats are primarily nocturnal, spending daylight hours sleeping for roughly 12–14 hours with frequent short naps. Their rest cycles are polyphasic, alternating sleep and brief activity throughout the day.
When do rats sleep? - in detail
Rats are primarily nocturnal mammals, displaying peak activity during the dark phase of a 24‑hour cycle. Their sleep periods concentrate in the light interval, with most individuals entering rest shortly after lights turn on and resuming activity near dusk. In laboratory settings that use a standard 12‑hour light/12‑hour dark schedule, sleep typically begins within the first two hours of the light period and can extend for 6–8 hours, interspersed with brief awakenings.
Sleep architecture in these rodents consists of alternating non‑rapid eye movement (NREM) and rapid eye movement (REM) episodes. A typical cycle lasts 10–15 minutes, repeating throughout the rest phase. NREM dominates the early portion of the sleep bout, while REM episodes increase in frequency toward the end of the sleep period. Total daily sleep time averages 12–14 hours, reflecting a polyphasic pattern with multiple short naps rather than a single consolidated block.
Factors that modify the timing and duration include:
- Light intensity: Dim lighting delays sleep onset; bright illumination accelerates it.
- Age: Juvenile rats exhibit longer total sleep (up to 16 hours) and more frequent REM bouts; seniors show reduced REM proportion.
- Sex: Males generally sleep slightly longer than females under identical conditions.
- Housing density: Crowded cages increase fragmentation, shortening individual sleep episodes.
- Feeding schedule: Access to food during the dark phase can shift activity peaks, marginally reducing daytime sleep.
In natural habitats, the same pattern persists: rats retreat to burrows or concealed nests at sunrise, remain dormant through daylight, and emerge at twilight to forage. Their circadian clock, regulated by the suprachiasmatic nucleus, synchronizes physiological processes to the external light-dark cycle, ensuring that sleep aligns with periods of low predation risk and reduced foraging efficiency.