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. Author manuscript; available in PMC: 2022 Jan 7.
Published in final edited form as: Dokl Biol Sci. 2012 Jul 5;444:188–191. doi: 10.1134/S0012496612030143

Characteristic of sleep and wakefulness in a walrus

Parameter Sleep on land, N = 5 Sleep in water, N = 3
Total sleep time, % of 24-h 26.3 ± 1.9 (21.9, 31.3) 21.6 ± 1.4 (19.2, 23.9)
Slow wave sleep (SWS), % of 24-h 19.4 ± 2.0 (15.5, 24.4) 20.5 ± 0.8 (19.0, 21.8)
Paradoxical sleep (PS), % of 24-h 6.9 ± 1.1 (5.5, 7.8) 1.1 ± 0.6 (0.1, 2.1)
Duration of bilateral SWS, % total SWS 90.2 ± 2.1 (85.6, 96.1) 96.7 ± 0.9 (95.8, 98.5)
Number of PS episodes during the 24-h period 15 ± 2 (11, 21) 13 ± 4* (9, 16)
Duration of PS episodes, min** 6.4 ± 0.6 (0.3, 22.7) 1.8 ± 0.1 (0.7, 3.3)

Note: The data presented as mean ± SEM. Minimal and maximal values are given in parentheses. N—number of recording sessions (days).

*

The mean values were calculated for the 2nd and 3rd recording days. Only one episode lasting 2.0 min was recorded on the first day.

**

The durations of PS episodes on land and in water were calculated for all recorded episodes—76 episodes when on land and 26 episodes when in water.