Figure 1 |. Duration of rest behaviour in whales and dolphins.
a, b, Time spent by killer whales floating at the surface and lying on the bottom of the pool (a) and by bottlenose dolphins floating at the surface (b). The data represent percentages of the night, the main sleep period in captive cetaceans. Data for one non-pregnant orca female and one adult male are the averages (with s.e.m.) of 12 nights10. All other killer-whale, dolphin and calf data are averages over two consecutive nights. Red, mothers; yellow, calves; blues, adult females without calves; green, adult males.