Bill Barklow thinks hippos, although they do have vocal cords, may also release sounds into the water through a roll of fat in their throats. Ken Norris of the University of California at Santa Cruz examined dolphin skulls to find evidence that sounds are conducted through the lower jaw to the dolphin's ears. Barklow found similar structures in hippos that he believes may make it possible for hippos to listen to sounds above the surface with their ears while simultaneously monitoring underwater sounds through its submerged jaw. They have a close blood match. Jerold Lowenstein of the University of California at San Francisco has compared blood serum of whales with many ungulates, including cattle, pigs, and gazelles.
Most whales can ingest vast quantities of food through mouths that match their enormous size.
Beaked whales, however, have small mouths and little or no teeth, but they still manage to devour squid and fish. He placed his hand over the whale's mouth which sucked it up like a dustball. Beaked whales use suction, as nurse sharks do, to swallow their prey. John Heyning and James Mead have also made a curious discovery about the gray whale's mouth. Slurping up krill in the Arctic Ocean should quickly chill the animal like eating ice cream in winter does to humans.