When do rats go to sleep? - briefly
Rats are nocturnal; they begin activity at dusk and stay awake throughout the night. They typically rest during daylight hours, sleeping from early morning until early evening.
When do rats go to sleep? - in detail
Rats are primarily nocturnal; their activity peaks during darkness and sleep predominates in the light phase. In a standard 12 h light/12 h dark cycle, the majority of sleep begins within the first two hours after lights are turned on and continues for most of the daylight period.
Sleep in rats consists of alternating bouts of rapid eye movement (REM) and non‑REM (NREM) stages. A typical adult laboratory rat accumulates 10–14 hours of total sleep per 24‑hour period, divided into multiple episodes lasting 5–30 minutes each. REM periods are brief, usually 1–2 minutes, and recur every 10–15 minutes of NREM.
Factors that modify the timing and duration of rat sleep include:
- Light intensity and timing: sudden illumination suppresses sleep; dim light prolongs it.
- Food availability: scheduled feeding can shift sleep onset earlier or later.
- Age: younger rats exhibit longer total sleep time; older individuals show reduced REM proportion.
- Strain: some genetic lines display higher nocturnal activity and shorter daytime sleep.
- Environmental stressors: noise, temperature fluctuations, and cage enrichment alter bout length and fragmentation.
Laboratory recordings using electroencephalography confirm that the first major sleep episode starts shortly after the light phase begins, with a gradual increase in sleep depth throughout the morning. By mid‑day, rats reach peak NREM intensity, followed by intermittent REM bursts. As the dark phase approaches, activity rises and sleep episodes become increasingly sparse.
In summary, rats consolidate most of their sleep during daylight, initiating rest within the early light period and maintaining a fragmented yet predictable pattern influenced by environmental cues, physiological state, and genetic background.