Fig. 3.

Rest on the bottom of pools in a captive killer whale (photo by O.I. Lyamin), beluga (from Lyamin et al., 2002b) and bottlenose dolphin (from Sekiguchi and Kohshima, 2003).

Rest on the bottom of pools in a captive killer whale (photo by O.I. Lyamin), beluga (from Lyamin et al., 2002b) and bottlenose dolphin (from Sekiguchi and Kohshima, 2003).