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. But when the scientists dissected a gray whale tongue they discovered blood vessels clustered around the arteries that carry warm blood from the heart. As the blood circulates, its warmth is passed from the arteries which carry blood from the heart, to the surrounding vessels, which carry blood returning to the heart. Recently, though, other researchers have come to doubt this theory.