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Polygrams of main behavioral states in a walrus while on land (a) and in water (b). EEG—electroencephalogram of the left (L) and right (R) hemispheres. EMG—electromyogram of neck muscles. ECG—instantaneous heart rate (beats per min). B – respiratory acts (breaths). PS—paradoxical sleep. During breath holdings (apneas) the walrus submerged and lay on the bottom of pool.
