W hales have lungs, not gills, so they must come to the surface of the ocean to breathe. They spend most of their lives on the surface, but some species can dive at least a half mile in pursuit of food. A thick blanket of fatty blubber insulates the warm-blooded animal against cold seawater. The seasonal distribution and density of zooplankton, a main component of the whale diet, in various regions of the ocean are major factors influencing whale migration patterns. S ome species of small toothed whales are highly social, traveling in schools, and are apparently capable of engaging in simple communication with other members of the school.
Whales produce two basic types of underwater sounds that presumably serve two different purposes.
Low-pitched signals, such as barks, whistles, screams, and moans, are audible to humans and are believed to be used in social communication. Other sounds are brief clicks of high intensity that have a wide range in frequency, with some sounds having more than ten times the highest frequency audible to humans. These sounds are used for purposes of echolocation. Echolocation has been widely recognized as a means of navigating and of locating and identifying food sources. L ike dolphins and porpoises, some whales can be playful.