What makes them mammals?
Whales and dolphins are mammals in that they breathe air, give birth to live young (not hatched from eggs), nurse their babies, and they are warm-blooded. Mammals also have hair or fur, but the most that can be found on whales and dolphins are usually a few whiskers around the snout of some newborns. Even this small remnant of hair usually falls out within a few weeks, leaving only small pits behind.
What adaptations have made marine mammals successful at ocean living?
Proof that long-ago relatives were land animals can be found in the vestigial tails in embryonic whales and in the bones in whales' flippers that look like human hands. But in most ways, whales and dolphins are supremely suited for life in the sea, with their:
- streamlined shape for efficient movement through viscous medium, with no protruding ears, and little or no hair to slow them down
- insulating blubber, a thick layer of fat and oil, which keeps their bodies warm and buoyant. This layer is thinner in warmer temperatures, and thicker in colder climates.
- soft skin that sloughs off constantly
- limbs evolved into fins and flippers dorsal fin for balance, side flippers for balance and steering, tail fluke's up and down movement provides powerful propulsion through the water
- deep diving ability, due to:
- the proteins in muscles use and store oxygen efficiently
- their ability to tolerate high levels of carbon dioxide
- fact that their rib cages collapse to compress further for deep dives
- slower heartbeat while diving
- blood is shunted away from areas that can tolerate low oxygen and to heart, lungs, brain where it is needed most
- blowhole on top allows animal to surface to breathe while keeping most of body underwater
- camouflage coloration/countershading--dark top blends in with dark depths when viewed from above; light belly blends in with sunlit surface when seen from below
- ability to communicate over hundreds, even thousands of miles underwater
- echolocation which makes them able to avoid obstacles and find prey in murky depths
How do beaked whales feed?
Baleen whales strain plankton through their bristly baleen; toothed whales swallow their prey in huge gulps. 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. How can they gobble up their meals through their dainty mouths? Photo: credit Nan Hauser & Hoyt Peckham, CCRC
John Heyning, curator at the Natural History Museum of Los Angeles County, climbed into the tank of a rescued Hubb's beaked whale to find out for himself. 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.
Heyning and James Mead, curator of mammals at the National Museum of Natural History, have determined that beaked whales "use their tongues like pistons to suck in their prey."
(source: "Suction Power," National Wildlife, Oct/Nov, 1997)
How do feeding whales keep warm in frigid water?
John Heyning and James Mead have also made a curious discovery about the gray whale's mouth. A gray whale's five-foot-long tongue makes up fully 5% of its body surface area, a significant part of its body to be dragging through icy-cold waters. 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. These heat-conserving countercurrent exchanges are also found in other whale extremities-fins and flukes. (source: "Mighty Mouths: How Whales Keep the Heat," Science News, Nov. 8, 1997)
For a more detailed look at mammalian characteristics, see Animal Diversity Web