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| NOAA |
| A bottlenose dolphin and her calf (left). A killer whale surfaces to look for seals on the ice. |
It is hard to study cetacean sounds because there are usually no obvious signs that show which marine mammal is making the sound--even when they are close enough to see easily. Miniature recorders attached to the animals being studied that then detach after a few hours, such as the Dtag, have helped us get better recordings from individual animals. Peter Tyack, a behavioral biologist at Woods Hole Oceanographic Institution, devised vocalights to determine which dolphins in captivity were making sounds. The vocalight is attached to the bulging forehead of bottlenose dolphins, just above their snout, or rostrum, and light up when sounds are generated. Advanced technologies like this make it possible to better determine sound and response patterns between individuals rather than simply recording sounds without any clear knowledge of which specific animal is making the sound. Bottlenose dolphins (Tursiops truncatus)
Although there are more than 20 types of dolphins, bottlenose dolphins are the ones that most people think of when they think of dolphins. Bottlenose dolphins exist in oceans all over the world and are seen in movies, TV shows and in aquariums. In the wild, they can grow to as long as 4 m (13 ft) and live for 50 years or more. As cetaceans, or marine mammals, they share mammalian traits such as being warm-blooded, breathing air, giving birth to live young and feeding young with milk.
Bottlenose dolphins have excellent sight both in and out of the water. Their hearing is also excellent even though their small ear holes are hard to see. In fact, they actually hear through their jaw. Dolphins can produce sounds from inside their bulging forehead, called a melon. Dolphins make click sounds to find fish and whistles to communicate with each other. Scientists believe that individual dolphins have unique whistles, called a signature whistle.
Killer whales (Orcinus orca)
This "whale" is actually the largest of the dolphins, and is famous for ferocious feeding attacks on other whales. They usually eat seals, sea birds, and fish, and are the only cetaceans that regularly eat birds or mammals. They are commonly held in captivity and can grow to a length of 10 m (31 ft).
Recent detailed studies of fish-eating killer whales have shown that they stay with their mothers their whole lives, traveling in family pods. They produce a repertoire of calls that follow a consistent or stereotyped time-frequency pattern. The calls are actually made of two sounds that overlap, and are unique to each family group. To date, it is unknown whether individual whales within the pod sound different or not.
False killer whales (Pseudorca crassidens)
False killer whales are gregarious and are often found in groups of hundreds of animals. They feed on squid, large fish, and dolphins. Although not as thoroughly studied as some other whale species, they are found throughout the world and prefer mainly offshore waters in deep tropical, subtropical and warm temperate seas. They grow to about 6 m (18 ft) and are mostly black with occasional faint gray marks on the head and throat. They are also members of the dolphin family.
