A. Dolphins, porpoises, and whales all belong to a group of marine animals known as cetaceans. Like all mammals, cetaceans are warm-blooded, breathe air, and suckle their young. But how do you distinguish one from the other? The approximately 86 species of cetaceans in the world are placed in two main groups. Cetaceans range in size from the vaquita porpoise (found in the Gulf of California) growing to 1.4 meters long, up to the 30-meter long blue whale who is found in all the waters of the world. The blue whale is the largest animal that has ever existed on earth.

B. The waters around Australia range from the warm tropical waters of northern Australia to the cooler waters around the southern coastline. To the south of the continent are the colder subantarctic waters and off the Australian Antarctic Territory, the very cold, sometimes ice-strewn, Antarctic waters. The killer whale occurs in all waters though it is most abundant in the southern oceans. The other wide-ranging species, the bottlenose dolphin, occurs in all but the colder waters.

C. In many species, there are distinct breeding seasons. Males of some species may fight when competing for females, often resulting in distinct scarring on the body as in the case of Risso's dolphin. Gestation maybe ten months for the smaller species, and from twelve to sixteen months for some larger species. The young are usually born tail first. Often other dolphins will nudge the newborn to the surface for its first breath. Calves may be suckled for eight to sixteen months in the small species, to several years for the larger pilot whales. In most species, there appears to be a strong and prolonged bond between mother and young. Bottlenose dolphins may breed every two to three years. Other species may breed over different time scales.

D. Most small cetaceans feed on fish, squid or cuttlefish. Sperm whales and pilot whales feed mainly on squid taken at great depths. Some of the inshore species such as bottlenose dolphins eat fish, squid, cuttlefish, eels, and even prawns and starfish. A layer of blubber or fat under the skin acts as a reserve of energy and provides insulation. In warmer waters, species such as bottlenose dolphins may be able to catch sufficient food in a few hours of active hunting. In colder waters, the smaller species need more time to catch enough food to provide for their increased energy needs. Diving abilities vary greatly with some species taking most of their food in relatively shallow water, diving for only a few minutes at a time. Bottlenose dolphins dive deeper and are able to remain underwater for up to fifteen minutes. One of the large beaked whales has been known to dive to 2400 meters and remain submerged for over an hour.

E. Not given in any of the above paragraphs