Sleep and cardiac rhythm in the gray seal

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Science  14 Feb 1975:
Vol. 187, Issue 4176, pp. 553-555
DOI: 10.1126/science.163484


Telemetric studies of electroencephalograms, electrocardiograms, and electroculograms and concurrent observations of behavior revealed that seals can sleep underwater, on the surface, or while hauled out. Rapid eye movement preceded slow wave sleep and was accompanied by increased respiratory rate and rhythmic tachycardia. While slow wave sleep occurred under all sleep conditions, rapid eye movement occurred only when a seal was hanging at the water surface or hauled out, never underwater.

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