(A) During 10–14 days in seawater, the estimated deficit of REM sleep in fur seals reached 995%–1,370% of the daily baseline amount. Different seals are coded by color, and average values are shown as gray bars. The dotted lines connect the last day in seawater (the 10th, 11th, or 14th) and the first recovery day in each seal.
(B) Despite their REM sleep loss, only two out of four seals (marked blue and brown) displayed a substantial increase in REM sleep beyond baseline values after return to baseline conditions. In two other seals (labeled light green and dark blue), REM sleep amounts were similar to the daily variation seen under baseline conditions. Average values are shown as mean ± SEM (see also Table S3). See also Table S4.